Polymer compositions with enhanced radiopacity
10590218 ยท 2020-03-17
Assignee
Inventors
Cpc classification
A61L2400/16
HUMAN NECESSITIES
A61L29/041
HUMAN NECESSITIES
A61L29/18
HUMAN NECESSITIES
A61L31/18
HUMAN NECESSITIES
C08F220/303
CHEMISTRY; METALLURGY
A61K49/0442
HUMAN NECESSITIES
A61L31/048
HUMAN NECESSITIES
International classification
A61L29/18
HUMAN NECESSITIES
C08F220/30
CHEMISTRY; METALLURGY
A61L31/18
HUMAN NECESSITIES
Abstract
Radiopaque polymer compositions and methods for making the compositions are provided. These radiopaque polymer compositions include polymer compositions comprising a crosslinked polymer network, the network comprising a first repeating unit derived from a monofunctional monomer and a second repeating unit derived from a crosslinker monomer or oligomer having more than two polymerizable groups. Devices formed from radiopaque polymer compositions are also provided.
Claims
1. A polymer composition comprising a crosslinked network, the network comprising a) a plurality of first repeating units derived from a first reagent, the first reagent comprising a monomer having the structure of Formula 1, Formula 1-A, Formula 1-B or Formula 1-C; ##STR00032## wherein X is Br or I; m in Formula 1-C is 1-5; each R.sup.11 is independently a substituted or unsubstituted C.sub.2-C.sub.36 alkylene group; C.sub.3-C.sub.36 cycloalkylene group; C.sub.2-C.sub.36 alkenylene group; C.sub.3-C.sub.36 cycloalkenylene group; C.sub.2-C.sub.36 alkynylene group; C.sub.5-C.sub.36 arylene group; or C.sub.5-C.sub.36 heteroarylene group; each L.sup.11 is independently a single bond; (CH.sub.2).sub.q; (HCCH).sub.q; O; S; SO; SO.sub.2; SO.sub.3; OSO.sub.2; NR.sup.12; CO; COO; OCO; OCOO; CONR.sup.13; NR.sup.14CO; OCONR.sup.15, NR.sup.16COO, or NR.sup.17CONR.sup.18; each Ar.sup.11 is independently an iodine-, bromine or bismuth-containing C.sub.5-C.sub.36 aryl group containing one or more rings, or an iodine-, bromine or bismuth-containing C.sub.5-C.sub.36 heteroaryl group containing one or more rings; each of R.sup.12-R.sup.18 is independently hydrogen or a C.sub.1-C.sub.10 alkyl group; each q is independently an integer selected from the range of 1 to 10; b) a plurality of second repeating units derived from a second reagent, the second reagent comprising a branched monomer or oligomer comprising at least three terminal polymerizable groups but not comprising iodine, bromine or bismuth, wherein the branched monomer of the second reagent comprises a central portion R.sup.1 linked to at least two end portions, Y.sup.1 and Y.sup.2, at least one of the end portions being branched, wherein both Y.sup.1 and Y.sup.2 are represented by the structure of ##STR00033## wherein R.sup.1 is C.sub.6 to C.sub.20 alkylene, and wherein the central portion R.sup.1 is linked to the end portions Y.sup.1 and Y.sup.2 through linker L.sup.1, wherein L.sup.1 is a single bond, (CH.sub.2).sub.n, (HCCH).sub.n, O, S, SO, SO.sub.2, SO.sub.3, OSO.sub.2, NR.sup.3, CO, COO, OCO, OCOO, CONR.sup.4, NR.sup.5CO, OCONR.sup.6, NR.sup.7COO, or NR.sup.8CONR.sup.9 and each of R.sup.3-R.sup.9 is independently hydrogen or C.sub.1-C.sub.10 alkyl; and c) a plurality of third repeating units derived from a third reagent, the third reagent comprising a monomer having at least two terminal polymerizable groups.
2. The polymer composition of claim 1, wherein the second reagent comprises a branched monomer selected from the group consisting of: ##STR00034##
3. The polymer composition of claim 1, wherein the monomer of the first reagent has the formula ##STR00035## where r is an integer from 2 to 18.
4. The polymer composition of claim 3, wherein r is from 3 to 8.
5. The polymer composition of claim 1, wherein from 60 to 90 wt % of the first reagent is present in the composition.
6. The polymer composition of claim 1, wherein the third reagent comprises a monomer having the structure of Formula 14: ##STR00036## wherein R.sup.21 is a substituted or unsubstituted C.sub.2-C.sub.36 alkylene group; C.sub.3-C.sub.36 cycloalkylene group; C.sub.2-C.sub.36 alkenylene group; C.sub.3-C.sub.36 cycloalkenylene group; C.sub.2-C.sub.36 alkynylene group; C.sub.5-C.sub.36 arylene group; C.sub.5-C.sub.36 heteroarylene group; Formula 3; Formula 4 or Formula 5; ##STR00037## where in Formula 3, each R.sup.23 is independently a C4-C20 alkylene group and each n1 is independently an integer from 1 to 50; ##STR00038## where in Formula 4, each R.sup.24 is independently a C3-C20 alkylene group and each n2 is independently an integer from 1 to 50.
7. The polymer composition of claim 1, wherein from 60 to 90 wt % of the plurality of first repeating units are present in the crosslinked network.
8. A method of making a crosslinked polymer composition, the method comprising the steps of: a) forming a polymer precursor mixture comprising i) a first reagent comprising a monomer having the structure of Formula 1, Formula 1-A, Formula 1-B or Formula 1-C; ##STR00039## wherein X is Br or I; m in Formula 1-C is 1-5; each R.sup.11 is independently a substituted or unsubstituted C.sub.2-C.sub.36 alkylene group; C.sub.3-C.sub.36 cycloalkylene group; C.sub.2-C.sub.36 alkenylene group; C.sub.3-C.sub.36 cycloalkenylene group; C.sub.2-C.sub.36 alkynylene group; C.sub.5-C.sub.36 arylene group; or C.sub.5-C.sub.36 heteroarylene group; each L.sup.11 is independently a single bond; (CH.sub.2).sub.q; (HCCH).sub.q; O; S; SO; SO.sub.2; SO.sub.3; OSO.sub.2; NR.sup.12; CO; COO; OCO; OCOO; CONR.sup.13; NR.sup.14CO; OCONR.sup.15, NR.sup.16COO, or NR.sup.17CONR.sup.18; each Ar.sup.11 is independently an iodine-, bromine or bismuth-containing C.sub.5-C.sub.36 aryl group containing one or more rings, or an iodine-, bromine or bismuth-containing C.sub.5-C.sub.36 heteroaryl group containing one or more rings; each of R.sup.12-R.sup.18 is independently hydrogen or a C.sub.1-C.sub.10 alkyl group; each q is independently an integer selected from the range of 1 to 10; ii) a second reagent comprising a branched monomer or oligomer comprising at least three terminal polymerizable groups but not comprising iodine, bromine or bismuth, wherein the branched monomer of the second reagent comprises a central portion R.sup.1 linked to at least two end portions, Y.sup.1 and Y.sup.2, at least one of the end portions being branched, wherein both Y.sup.1 and Y.sup.2 are represented by the structure of ##STR00040## wherein R.sup.1 is C.sub.6 to C.sub.20 alkylene, and wherein the central portion R.sup.1 is linked to the end portions Y.sup.1 and Y.sup.2 through linker L.sup.1, wherein L.sup.1 is a single bond, (CH.sub.2).sub.n, (HCCH).sub.n, O, S, SO, SO.sub.2, SO.sub.3, OSO.sub.2, NR.sup.3, CO, COO, OCO, OCOO, CONR.sup.4, NR.sup.5CO, OCONR.sup.6, NR.sup.7COO, or NR.sup.8CONR.sup.9 and each of R.sup.3-R.sup.9 is independently hydrogen or C.sub.1-C.sub.10 alkyl; and iii) a third reagent comprising a monomer having at least two terminal polymerizable groups, and b) polymerizing the polymer precursor mixture with an initiator.
9. The method of claim 8, wherein from 60 to 90 wt % of the first reagent is present in the polymer precursor mixture.
10. A radiopaque polymer device for medical applications, the device or a device feature comprising a polymer composition according to claim 1.
11. The device of claim 10 wherein the polymer exhibits a glass transition temperature (Tg) and a Tan Delta (Loss Modulus/Storage Modulus ratio) curve related to temperature; the polymer's maximum rate of shape change occurs at an environmental operating temperature (To) that is coincident with the temperature at which the material's Tan Delta value is 60% of its peak value, above Tg.
12. The device of claim 10 for purposes of an indwelling, permanent implant to provide the function of: a. opening, or maintaining an open anatomical lumen; or b. closing an anatomical lumen, either partially as a valve, or complete lumen occlusion for any physiological fluid or gas flow or for an applied therapeutic fluid or gas flow; or c. support of an anatomical structure to assist in therapeutic restoration of an organ, vascular, digestive, excrement, or airway function; or d. support of an anatomical structure to assist in therapeutic restoration of an orthopaedic, maxiofacial, spinal, joint or other skeletal or function; or e. to support hemostasis by covering an area after tissue dissection or resection, a patch.
13. The device of claim 10 for purposes of a diagnostic or therapeutic instrument or device to provide the function of: a. a catheter for the purposes of accessing an anatomical location; delivering another device and/or therapeutic agent; or controlling the access or delivery of another device and/or therapeutic agent; or b. a temporarily indwelling device to provide a limited time therapeutic benefit left indwelling for a period of time and subsequently removed when the therapeutic period is completed.
14. The polymer composition of claim 1, wherein Ar.sup.11 is an iodine containing C.sub.6 aryl with 3 to 5 iodine atoms attached directly to the aryl ring.
15. The polymer composition of claim 14 wherein R.sup.11 is an C.sub.6-C.sub.36 alkylene group.
16. The polymer composition of claim 14, wherein R.sup.11 is an C.sub.6-C.sub.24 alkylene group.
Description
BRIEF DESCRIPTION OF THE FIGURES
(1)
(2)
(3)
(4)
(5)
DETAILED DESCRIPTION OF THE INVENTION
(6) As used herein, a crosslinked network is a polymer composition comprising a plurality of polymer chains wherein a large portion (e.g., 80%) and optionally all the polymer chains are interconnected, for example via covalent crosslinking, to form a single polymer composition. In an embodiment, the invention provides a radiopaque polymer in the form of a crosslinked network in which at least some of the crosslinks of the network structure are formed by covalent bonds. Radiopacity refers to the relative inability of electromagnetism, particularly X-rays, to pass through dense materials. The two main factors contributing to a material's radiopacity are density and atomic number of the radiopaque element. In an embodiment, this invention utilizes incorporated (trapped) iodine molecules within the polymer matrix to induce radiopaque functionality. In an embodiment, the radiopaque polymer is an iodinated polymer. As referred to herein, iodinated polymers are produced by incorporating (trapping) iodine molecules on a select monomer prior to formulation of the monomer into a polymer. Although iodine is used in some examples and descriptions herein, it is recognized that other radiopaque materials may be used, such as Bi and Br and that the descriptions here apply to and may be used with other radiopaque materials.
(7) As referred to herein, a monomer or monomer reagent is a reagent which can undergo polymerization under appropriate conditions. A monomer reagent comprises at least one monomer molecule, where a monomer molecule is a molecule which can undergo polymerization, thereby contributing constitutional units to the structure of a macromolecule or oligomer. In an embodiment, a monomer reagent may be represented by an average or dominant chemical structure and comprise monomer molecules having that chemical structure but may also contain components with other chemical structures. For example, a monomer reagent may comprise impurities having chemical structures other than the average or dominant structure of the reagent. An oligomer or oligomeric reagent is also a reagent which can undergo polymerization under appropriate conditions. An oligomeric reagent comprises an oligomer molecule, the oligomer molecule comprising a small plurality of units derived from molecules of lower relative molecular mass. In an embodiment, certain hyperbranched crosslinking reagents suitable for use with the invention may be regarded as oligomeric reagents.
(8) As is known in the art, the chemical structures of the compositions shown are intended to be representation of average or dominant structures. In an embodiment, a monomer or oligomer reagent may be represented by an average or dominant chemical structure and comprise components having that chemical structure, but may also contain components with other chemical structures. For example, when a monomer or oligomer reagent functionalized with polymerizable groups is formed through reaction of a first component with a second component comprising polymerizable groups, the resulting product may vary due to impurities present in the two components and/or due to variation in the extent of reaction between the two components. In an embodiment, extent of reaction between the two components is limited so that at least some of the reaction products include less than the maximum number of possible polymerizable groups. In an embodiment, for example, all structures involving the pentaerythritol triacrylate appendages are average structures.
(9) In an embodiment, the iodinated crosslinked polymers of the invention are formed by the polymerization of a polymer precursor mixture comprising an iodinated monofunctional monomer, a multifunctional crosslinker monomer or oligomer having more than two polymerizable groups, and an initiator. The polymer precursor mixture may also comprise one or more additional iodinated monofunctional monomers, one or more additional crosslinker monomers or oligomers, and/or one or more additional monofunctional monomers. As used herein, monofunctional refers to a monomer containing only one polymerizable group, while multifunctional refers to a monomer containing more than one polymerizable group.
(10) In an embodiment, the monofunctional iodinated monomer comprises an acrylate polymerizable group. In another embodiment, the monofunctional iodinated monomer comprises a styrene, acrylamide, or methacrylamide polymerizable group. In an embodiment, the polymerizable group is a terminal or end group.
(11) As used herein, an iodinated monomer comprises an iodine-containing moiety. In an embodiment, the iodinated monomer comprises an iodine-containing moiety which is an iodinated aryl or heteroaryl group. In an embodiment, the iodine-containing moiety is C.sub.5-C.sub.30 aryl or C.sub.5-C.sub.30 heteroaryl having at least 1 iodine atom. In an embodiment, the iodine-containing moiety is C.sub.5-C.sub.30 aryl or C.sub.5-C.sub.30 heteroaryl having at least 2 iodine atoms. In an embodiment, the iodine-containing moiety is C.sub.5-C.sub.30 aryl or C.sub.5-C.sub.30 heteroaryl having at least 3 iodine atoms. In an embodiment, the iodine-containing moiety is C.sub.6 aryl with iodine atoms attached directly to the ring, with the number of iodine atoms being from 3 to 5. The description herein can be used for embodiments using Br or Bi as radiopaque moieties.
(12) In the description immediately below, the variables are used in the context of the immediate structures shown, as will be apparent to one of ordinary skill in the art.
(13) In an embodiment, the repeating unit derived from the first radiopaque monomer has the general formula:
(14) ##STR00016##
(15) wherein R.sup.11 is independently a substituted or unsubstituted C.sub.2-C.sub.36 alkylene group; C.sub.3-C.sub.36 cycloalkylene group; C.sub.2-C.sub.36 alkenylene group; C.sub.3-C.sub.36 cycloalkenylene group; C.sub.2-C.sub.36 alkynylene group; C.sub.5-C.sub.36 arylene group; or C.sub.5-C.sub.36 heteroarylene group;
(16) each L.sup.11 is independently a single bond; (CH.sub.2).sub.q; (HCCH).sub.q; O; S; SO; SO.sub.2; SO.sub.3; OSO.sub.2; NR.sup.12; CO; COO; OCO; OCOO; CONR.sup.13; NR.sup.14CO; OCONR.sup.15, NR.sup.16COO, or NR.sup.17CONR.sup.18;
(17) each Ar.sup.11 is independently an iodine-, bromine or bismuth-containing C.sub.5-C.sub.36 aryl group containing one or more rings, or an iodine-, bromine or bismuth-containing C.sub.5-C.sub.36 heteroaryl group containing one or more rings;
(18) each of R.sup.12-R.sup.18 is independently hydrogen or a C.sub.1-C.sub.10 alkyl group; each q is independently an integer selected from the range of 1 to 10. In an embodiment, R.sup.11 is substituted or unsubstituted C.sub.2-C.sub.36 alkylene, C.sub.3-C.sub.36 cycloalkylene, C.sub.2-C.sub.36 alkenylene, C.sub.3-C.sub.36 cycloalkenylene, C.sub.2-C.sub.36 alkynylene, C.sub.5-C.sub.36 arylene, or C.sub.5-C.sub.36 heteroarylene; L.sup.11 is a single bond, (OH.sub.2).sub.n, (HCCH).sub.n, O, S, SO, SO.sub.2, SO.sub.3, OSO.sub.2, NR.sup.2, CO, COO, OCO, OCOO, CONR.sup.3, NR.sup.4CO, OCONR.sup.5, NR.sup.6COO, or NR.sup.7CONR.sup.8; Ar.sup.11 is an iodinated C.sub.5-C.sub.36 aryl or C.sub.5-C.sub.36 heteroaryl; and each of R.sup.12-R.sup.18 is independently hydrogen or C.sub.1-C.sub.10 alkyl; n is an integer selected from the range of 1 to 10. In an embodiment, L.sup.11 is ester or amide. In an embodiment, the first repeating unit is derived from an iodinated monofunctional monomer comprising iodinated C.sub.5-C.sub.36 aryl or C.sub.5-C.sub.36 heteroaryl.
(19) In an embodiment, a second repeating unit in the polymer is derived from a crosslinking reagent comprising a non-iodinated multifunctional crosslinker monomer or oligomer. In another embodiment, the repeating unit derived from the crosslinker monomer has the general average formula 16-A below:
(20) ##STR00017##
wherein R.sup.1 is as defined for Formula 2.
(21) In another embodiment, the repeating unit derived from the crosslinker has the average general formula (Formula 16-B), wherein R.sup.1 is as defined for Formula 2. R.sup.7 in Formula 6-A is substituted or unsubstituted C.sub.2-C.sub.36 alkylene, C.sub.3-C.sub.36 cycloalkylene, C.sub.2-C.sub.36 alkenylene, C.sub.3-C.sub.36 cycloalkenylene, C.sub.2-C.sub.36 alkynylene, C.sub.5-C.sub.36 arylene, C.sub.5-C.sub.36 heteroarylene, an oligomeric polyether, (Formula 3) an oligomeric polycarbonate (Formula 4), or an oligomeric polyurethane (Formula 5), wherein R.sup.3 in Formula 3 is C.sub.4-C.sub.20 alkylene and n1 is an integer from 1 to 50 or wherein R.sup.4 in Formula 4 is C.sub.3-C.sub.20 alkylene and n2 is an integer from 1 to 50 or wherein where R.sup.5 in Formula 5 is aliphatic group, substituted or unsubstituted C.sub.2-C.sub.36 alkylene, C.sub.3-C.sub.36 cycloalkylene, C.sub.2-C.sub.36 alkenylene, C.sub.3-C.sub.36 cycloalkenylene, C.sub.2-C.sub.36 alkynylene, C.sub.5-C.sub.36 arylene, C.sub.5-C.sub.36 heteroarylene, aromatic group, polyalkyl siloxane group, polyether group, polyester group, polycarbonate group or a combination of linear or branched aliphatic groups and aromatic groups and n3 is an integer from 1 to 50.
(22) ##STR00018##
(23) In another embodiment, the repeating unit derived from the crosslinker monomer has the general formula (Formula 16-C), wherein the pentaerythritol moieties are attached by ester linkages to a central trimesic (with 1,3,5-substitution pattern; 1,2,4-substitution is also available commercially) acid moiety that is an aromatic group and the resultant crosslinker average structure is nonafunctional (having nine functional groups).
(24) ##STR00019##
(25) In another embodiment, the repeating unit derived from the crosslinker monomer has the general formula shown in Formula 16-D, in which a central toluene-2,4,6-triisocyanate core reacted with pentaerythritol triacrylate produces an averaged structure that is a nonafunctional crosslinker with urethane linkages to the aromatic core moiety:
(26) ##STR00020##
(27) In another embodiment, the repeating unit derived from the crosslinker monomer has the general average trifunctional formula (Formula 16-E),
(28) ##STR00021##
in which R.sup.8, R.sup.9 and R.sup.10 are as defined for formula 2-F. As appreciated by those skilled in the art, R.sup.8, R.sup.9 and R.sup.10 in Formula 16-E can be, in whole or part, substituted for the multi-functional pentaerythritol moiety seen in Formulas 16-A, 16-B, 16-C and 16-D to generate a penta-acrylate to nona-acrylate crosslinker, and the 1,1,1-tris-(4-isocyanatophenyl)-methane core of the Formula 16-E crosslinker can be substituted for the toluene 2,3,5-triisocyanate core of the Formula 16-E crosslinker. The structure shown in Formula 16-E can be optimized by adjusting the carbon number of R.sup.8, R.sup.9 and R.sup.10 using the same chemistry approach used to generate the different R.sup.1 segment lengths for the radiopaque iodinated monomer, and in so doing provide additional distance between crosslinks to alleviate brittleness while allowing for durable, reversible H-bonding contribution of the urethane groups to total network reinforcement.
(29) Though Formulas 16-A, 16-B, 16-C, 16-D and 16-E are all non-iodinated and comprised in part of pentaerythritol triacrylate clustered crosslinker groups, exemplify hexa- and nona-functional acrylate clustered crosslinkers with central aromatic and non-aromatic cores and are averaged structures as assembled, the description and structures are not intended to be limiting in terms of: 1) functionality, the extreme being dendrimers with an unlimited number of branches, 2) linkage type between the polymerizable groups and the center segment, or 3) random averaged structures vs. well-defined controlled structures, as is understood by those skilled in the art.
(30) The clustered crosslinkers in 16-A, 16-B, 16-C, 16-D and 16-E, for example, provide a means of achieving higher crosslink density than a bifunctional crosslinker while the spacer segment retains a means of imparting flexibility to avoid brittleness.
(31) In an embodiment, the non-iodinated polyfunctional crosslinker monomer has a central segment that is an oligomeric polyester, an oligomeric polycarbonate or an oligomeric polyurethane. In an embodiment, the molecular weight of the oligomer is less than 1000. In an embodiment, the molecular weight of the oligomer is greater than or equal to 100 and less than 1000. In an embodiment, the molecular weight of the oligomer is greater than or equal to 500 and less than 1000. In an embodiment, the molecular weight of the oligomer is any molecular weight that produces a composition having properties that are useful in the desired use. In an embodiment, the molecular weight of the oligomer is greater than 1000 and less than 10,000. The molecular weight of the oligomer may be greater than 1000 and less than 2500, greater than 1500 and less than 2500, or greater than 2000 and less than 2500. In an embodiment, the dispersity or polydispersity index may be from 1.0 to 10. In an embodiment, the oligomeric center segment is a poly (C.sub.2-C.sub.36 carbonate). In another embodiment, the center segment comprises a polycondensate of one or more compounds selected from the group consisting of: diacid chloride, diol, diisocyanate, and bis-chloroformate. In an embodiment, the number of atoms in the central segment may be from 10 to 100. The compounds used to form the polycondensate can be linear or branched aliphatic, cycloaliphatic, partially cycloaliphatic or partially aromatic. In an embodiment, the compounds used to form the polycondensate may be linear or branched aliphatic or cycloaliphatic.
(32) The polymer network may also comprise repeating units derived from at least two crosslinker monomers or oligomers, both or one of which have a functionality higher than two. The two crosslinker monomers or oligomers may be any suitable structure shown or described here. The repeating units from one of the crosslinker monomers may be derived from diacrylate crosslinker monomers. In addition to Formulas 2 and 3, the repeating units for a second crosslinker monomer of a bifunctional type may be described by Formula 17-A:
(33) ##STR00022##
wherein R.sup.14 in Formula 17-A is substituted or unsubstituted C.sub.2-C.sub.36 alkylene, C.sub.3-C.sub.36 cycloalkylene, C.sub.2-C.sub.36 alkenylene, C.sub.3-C.sub.36 cycloalkenylene, C.sub.2-C.sub.36 alkynylene, C.sub.5-C.sub.36 arylene, C.sub.5-C.sub.36 heteroarylene, an oligomeric polyester, an oligomeric polycarbonate, or an oligomeric polyurethane.
(34) The polymer network may further comprise a repeating unit derived from a monofunctional non-iodinated monomer. In an embodiment, this repeating unit may be described by Formula 5 or any suitable structure shown or described here.
(35) In an embodiment, the cross-linked polymer network comprises a repeating unit derived from a monofunctional iodinated monomer and a repeating unit derived from a multifunctional non-iodinated crosslinker monomer or oligomer having more than two polymerizable groups. In an embodiment, the network may also comprise a repeating unit derived from a non-iodinated monofunctional co-monomer. In an embodiment, the repeating unit derived from this co-monomer may be described by the general formula:
(36) ##STR00023##
(37) In an embodiment R.sup.27 in Formula 18 is C.sub.2 to C.sub.36 alkyl. R.sup.27 in Formula 18 may be branched or unbranched.
(38) In another embodiment, the network may further comprise a repeating unit derived from an additional iodinated monomer. This repeating unit may be described by the general formula:
(39) ##STR00024##
(40) In an embodiment in Formula 19, R.sup.28 is substituted or unsubstituted C.sub.2-C.sub.36 alkylene, C.sub.3-C.sub.36 cycloalkylene, C.sub.2-C.sub.36 alkenylene, C.sub.3-C.sub.36 cycloalkenylene, C.sub.2-C.sub.36 alkynylene, C.sub.5-C.sub.36 arylene, or C.sub.5-C.sub.36 heteroarylene; L.sup.2 is a single bond, (CH.sub.2).sub.n, (HCCH).sub.n, O, S, SO, SO.sub.2, SO.sub.3, OSO.sub.2, NR.sup.2, CO, COO, OCO, OCOO, CONR.sup.3, NR.sup.4CO, OCONR.sup.5, NR.sup.6COO, or NR.sup.7CONR.sup.8;
(41) Ar.sup.2 is an iodinated C.sub.5-C.sub.30 aryl or C.sub.5-C.sub.30 heteroaryl having at least 3 iodine atoms; and
(42) each of R.sup.2-R.sup.8 is independently hydrogen or C.sub.1-C.sub.10 alkyl;
(43) n is an integer selected from the range of 1 to 10
(44) and R.sup.28 is other than R.sup.11.
(45) In embodiments, there is more than one crosslinker included in a composition. Examples of additional crosslinker monomers that can be included to any useful amount in the composition include: polycarbonate diacrylate, C10 diacrylate, and multiple others as described in WO 2012/019145, for example, along with the clustered crosslinkers described herein. In an embodiment, there is more than one crosslinker as described herein used in a composition.
(46) In another aspect, the invention also provides methods for making radiopaque polymers comprising a crosslinked network. In an embodiment, the method comprises the steps of forming a polymer precursor mixture comprising one or more first monomers described herein, one or more crosslinker monomers or oligomers described herein, a free radical initiator; and polymerizing the polymer precursor mixture.
(47) In a specific embodiment, the method comprises the steps of:
(48) a) forming a polymer precursor mixture comprising i) a first monomer having the general structure
(49) ##STR00025##
(50) R.sup.11 is independently a substituted or unsubstituted C.sub.2-C.sub.36 alkylene group; C.sub.3-C.sub.36 cycloalkylene group; C.sub.2-C.sub.36 alkenylene group; C.sub.3-C.sub.36 cycloalkenylene group; C.sub.2-C.sub.36 alkynylene group; C.sub.5-C.sub.36 arylene group; or C.sub.5-C.sub.36 heteroarylene group;
(51) each L.sup.11 is independently a single bond; (CH.sub.2).sub.q; (HCCH).sub.q; O; S; SO; SO.sub.2; SO.sub.3; OSO.sub.2; NR.sup.12; CO; COO; OCO; OCOO; CONR.sup.13; NR.sup.14CO; OCONR.sup.15, NR.sup.16COO, or NR.sup.17CONR.sup.18;
(52) each Ar.sup.11 is independently an iodine-, bromine or bismuth-containing C.sub.5-C.sub.36 aryl group containing one or more rings, or an iodine-, bromine or bismuth-containing C.sub.5-C.sub.36 heteroaryl group containing one or more rings;
(53) each of R.sup.12-R.sup.18 is independently hydrogen or a C.sub.1-C.sub.10 alkyl group;
(54) each q is independently an integer selected from the range of 1 to 10;
(55) a second monomer having the general average structure
(56) ##STR00026##
wherein R.sup.1 is substituted or unsubstituted C.sub.2-C.sub.36 alkylene, C.sub.3-C.sub.36 cycloalkylene, C.sub.2-C.sub.36 alkenylene, C.sub.3-C.sub.36 cycloalkenylene, C.sub.2-C.sub.36 alkynylene, C.sub.5-C.sub.36 arylene, C.sub.5-C.sub.36 heteroarylene, an oligomeric polyester, an oligomeric polycarbonate, an oligomeric polyurethane;
(57) ##STR00027##
Wherein R.sup.23 is as defined for Formula 3 above, R.sup.24 is as defined for Formula 4 above and R.sup.25 and R.sup.26 are as defined for Formula 5 above and ii) a free radical initiator; and
(58) b) polymerizing the polymer precursor mixture.
(59) In an embodiment, a first monomer is an iodinated monomer having one of the structures shown below:
(60) ##STR00028##
(61) The crosslinker monomer or oligomer, in combination with the other monomers in the mixture, allows formation of a crosslinked network. The structure and amount of crosslinker(s) in the polymer precursor mixture may be selected to provide a sufficiently high crosslink density to achieve the desired modulus in the composition. In different embodiments, the molecular weight of the crosslinker is in the range from 100 to 1000, 200 to 2000 or 200-5000, or any other useful molecular weight range. Blends of crosslinkers can allow shorter and longer crosslinkers to be used together.
(62) In an embodiment, the multifunctional crosslinker monomer or oligomer comprises a plurality of acrylate polymerizable groups. In another embodiment, the multifunctional iodinated monomer comprises a plurality of styrene, acrylamide, or methacrylamide polymerizable groups.
(63) In an embodiment, the crosslinker monomer or oligomer may be classified as hydrophobic. In an embodiment, a hydrophobic monomer or oligomer may be defined as being insoluble in water. In an embodiment, the crosslinker monomer or oligomer is less soluble in water than a poly(ethylene glycol) di(meth)acrylate of comparable molecular weight.
(64) An optional monofunctional non-iodinated co-monomer can be used to adjust the properties of the polymer. For example, the co-monomer can be used to modify the glass transition temperature (Tg) of the polymer. As another example, the co-monomer can be selected to assist in system compatibilization.
(65) In an embodiment, the co-monomer is a vinyl monomer. A wide range of commercially-available vinyl monomers can be utilized, including but not limited to butyl acrylate, which imparts a Tg value near 40 C. Such a low glass transition temperature can help to offset the typically higher Tg contribution of radiopaque monomer and crosslinkers having relatively low molecular weight values. The amenability of a wide cross section of vinyl monomers to polymerization or copolymerization by a free radical mechanism facilitates access to useful structure-property modifications.
(66) In an embodiment, the monofunctional co-monomer comprises an acrylate polymerizable group. In another embodiment, the monofunctional co-monomer comprises a styrene, acrylamide, or methacrylamide polymerizable group. In an embodiment, the polymerizable group is an end group. Though styrene monomers typically do not polymerize as aggressively and to as high a conversion as acrylates, in copolymerization reactions with acrylates styrene monomers propagate more readily and can be used to good advantage where required. In different embodiments, the amount of comonomer may be at least 50 wt %. In different embodiments, the amount of comonomer may be from 50-90 wt %, 50-80 wt %, 60-80 wt %, 60-90 wt %, 2.5-90 wt %, 5-50 wt %, 5-25 wt %, 25-50 wt %, 50-80 wt %, 10-50 wt %, 20-50 wt %, 50-99 wt %, 90-near 100 wt %, or 50-70 wt %, or any other range producing a functional end-product. In different embodiments, the amount of comonomer may be from 2.5-90 wt %, 5-80 wt %, 10-80 wt %, 20-90 wt %, 2.5-10 wt %, 5-50 wt %, 5-25 wt %, 25-50 wt %, 50-80 wt %, 10-50 wt %, 20-50 wt %, or 10-70 wt %, or any other range producing a functional end-product. In an embodiment, the comonomer is not present.
(67) In an embodiment, the number of repeating units in any repeating unit described or shown herein is not specifically limited, but is rather any number that is functionally feasible, that is, can be synthesized and has the desired use in the desired compositions, compounds, methods and devices. As a non-limiting example, the number of repeating units in the first repeating is between 1 and 10,000 in an embodiment. As a non-limiting example, the number of repeating units in the second repeating is between 5 and 10,000 in an embodiment.
(68) In an aspect, more than one monomer or oligomer is used to form repeating units characterized as first repeating unit, second repeating unit, etc. I In an embodiment of this aspect, the weight percentage of the first repeating unit is from 1-100 wt %, the weight percentage of the second repeating unit is from 5 to 90 wt % and the weight percentage of the third repeating unit is from 0 to 75 wt %. In an embodiment of this aspect, the weight percentage of the first repeating unit is from 20-90 wt %, the weight percentage of the second repeating unit is from 5 to 75 wt % and the weight percentage of the third repeating unit is from 5 to 75 wt %. In an embodiment of this aspect, the weight percentage of the first repeating unit is from 50-85 wt %, the weight percentage of the second repeating unit is from 10 to 55 wt % and the weight percentage of the third repeating unit is from 0 to 55 wt %. In an embodiment of this aspect, the weight percentage of the first repeating unit is from 30-75 wt %, the weight percentage of the second repeating unit is from 10 to 50 wt % and the weight percentage of the third repeating unit is from 10 to 50 wt %. In an embodiment of this aspect, the amount of the second repeating unit is between 65 and 85 wt %. As is recognized, any permutation of the components described that produces a functional final product can be used, even if not specifically described herein. In an embodiment of this aspect, the weight percentage of the first repeating unit is from 10-50 wt %, the weight percentage of the second repeating unit is from 65 to 85 wt %. In an embodiment of this aspect, the weight percentage of the first repeating unit is from 10-90 wt %, the weight percentage of the second repeating unit is from 90 to 10 wt %. It is understood that all lower, intermediate and higher values and ranges are included to the same extent as if they were included separately.
(69) In an embodiment, the amount of the first repeating unit is at least 50% of the total weight of the composition. In an embodiment, the amount of the first repeating unit is at most 50% of the total weight of the composition. In an embodiment, the amount of the first repeating unit is from 15-70 wt % of the total weight of the composition. In an embodiment, the amount of the first repeating unit is from 5-90 wt % of the total weight of the composition. In an embodiment, the amount of the first repeating unit is from 40-70 wt % of the total weight of the composition. In an embodiment, the amount of the second repeating unit is below 80 wt % of the total weight of the composition. In an embodiment, the amount of the second repeating unit is at most 50 wt % of the total weight of the composition. In an embodiment, the amount of the second repeating unit is at least 50 wt % of the total weight of the composition. In an embodiment, the amount of the second repeating unit is at most 40 wt % of the total weight of the composition. In an embodiment, the amount of the first repeating unit is from 40 wt %-70 wt % of the network, the amount of the second repeating unit is from 10 wt %-60 wt % of the network, and the amount of the third repeating unit is from 20 wt %-50 wt % of the network, with the total amounts of the first, second and third repeating units being 100 wt %. Any permutation of the components described where the total amounts of the second and third repeating units is 100 wt % can be used and is intended to be described to the same extent as if specifically described.
(70) In an embodiment, provided is a method for making a polymer composition comprising a crosslinked network, the method comprising the steps of: a) forming a polymer precursor mixture comprising a first monomer as described herein, a crosslinker monomer or oligomer as described herein, and a free radical initiator; and b) polymerizing the polymer precursor mixture. In an embodiment, the polymer precursor mixture is substantially homogeneous.
(71) In an embodiment, the amount of the radiopaque monomer in the monomer mixture is at least 5-10 wt %. In an embodiment, the amount of the radiopaque monomer in the polymer precursor mixture is at least 20 wt %. In an embodiment, the amount of the radiopaque monomer in the polymer precursor mixture is at least 25 wt %. In an embodiment, the amount of the radiopaque monomer in the polymer precursor mixture is at least 30 wt %. In an embodiment, the amount of the radiopaque monomer in the polymer precursor mixture is at least 50 wt % and can even reach 100%. In an embodiment, the amount of the crosslinker in the polymer precursor mixture is less than or equal to 80 wt %. In an embodiment, the amount of the crosslinker in the polymer precursor r mixture is less than or equal to 90 wt %. In an embodiment, the amount of the crosslinker in the polymer precursor mixture is less than or equal to 75 wt %. In another embodiment, the polymer precursor mixture comprises 40%-70 wt % of radiopaque monomer(s), 10-40 wt % crosslinker, and 20-50 wt % added co-monomer with the total amount including photoinitiator or other free radical initiator being 100 wt %. In an embodiment, the amount of initiator is less than 1 wt %. In an embodiment, the polymer precursor mixture comprises at least 60 wt % radiopaque monomer(s), and less than or equal to 40 wt % crosslinker(s). In an embodiment, the polymer precursor mixture comprises at least 50 wt % radiopaque monomer(s), and less 50 wt % crosslinker(s). As will be understood, any permutation of the components that produces a functional compound or composition can be used.
(72) A wide range of free radical initiating systems may be used for polymerization. In different embodiments, the initiator may be a photoinitiator, a thermal initiator or a redox (reduction oxidation) initiator. Photoinitiating systems are particularly useful, provided that a photoinitiator is chosen that does not require wavelengths of light that are absorbed excessively by the base monomer ingredients of the formulation. Irgacure 819 (Ciba (BASF), Bis(2,4,6-trimethylbenzoyl)-phenylphosphineoxide) is one example of a photoinitiator that has been found to be particularly useful for the curing system.
(73) Photopolymerization occurs when monomer solution is exposed to light of sufficient power and of a wavelength capable of initiating polymerization. The wavelengths and power of light useful to initiate polymerization depends on the initiator used. Light used in the invention includes any wavelength and power capable of initiating polymerization. Preferred wavelengths of light include ultraviolet. In different embodiments, the light source primarily provides light having a wavelength from 200 to 500 nm or from 200 to 400 nm. In an embodiment, 1-100 mW/cm.sup.2 of 200-500 nm light is applied for a time from 10 sec to 60 mins. Any suitable source may be used, including laser sources. The source may be filtered to the desired wavelength band. The source may be broadband or narrowband, or a combination. The light source may provide continuous or pulsed light during the process.
(74) Thermal initiating systems, with low-temperature or high-temperature initiators, common examples being benzoyl peroxide and azobisisobutyronitrile (AIBN), are also useful in situations where a particularly large or irregularly-shaped object that is difficult to illuminate uniformly is to be prepared. Also of use in the latter scenario are free radical initiating systems that produce free radicals by any type of redox reaction, such as the Fenton system involving ferrous salts with tert-butyl hydroperoxide, or other metal-organic, organic such as triethylamine+hydroperoxides, or photo-organic redox systems, an example of the latter being the Eosin-Y+triethanolamine visible light initiating system.
(75) A number of pseudo-living free radical polymerization systems, some of which are capable of producing polymers with narrower molecular weight distributions than conventional free radical polymerizations, are also described in the art and can be amenable to production of crosslinker segments for SMPs or for SMP curing. For example, styrene monomers that polymerize to low conversion in a conventional system may be driven to high conversion in a pseudo-living system. These pseudo-living systems typically involve variable combinations of reversible chain propagation-termination and/or chain transfer steps. Living free radical polymerizations known to the art include, but are not limited to, NMP, RAFT, and ATRP.
(76) Additionally; any other type of non-conventional free radical polymerization process, whether pseudo-living or not, that produces free radicals capable of initiating polymerization of the radiopaque and non-radiopaque monomers and crosslinkers comprising the SMPs of this invention, fall within the scope of potential initiating-polymerization methods. These and other free radical initiating systems are conceivable and known to those skilled in the art.
(77) In embodiments, examples of the useful initiating systems include anionic, cationic, free radical polymerizations that are non-living, pseudo-living or living as well as Ziegler-Natta and olefin metathesis. The use of these systems is known in the art. In an embodiment, these systems are useful if a prepolymerized segment is at least difunctional and has hydroxyl or other groups known in the art which can be used to attach polymerizable groups, including acrylate groups in an embodiment.
(78) In an embodiment, some or all of the components of the polymer precursor mixture are combined at a temperature greater than ambient temperature. In different embodiments, the initiator may be added at the same time as the monomer components or added just prior to or at the time of molding. In another embodiment where a thermal initiator is used, the polymer precursor mixture ingredients may be divided into two parts; wherein the high storage temperature ingredients are in Part A, and the lower storage temperature ingredients are in Part B. The thermal initiator may be added to the lower storage temperature ingredients in Part B at a storage temperature that is below the initiator's polymerization temperature. In an embodiment, forming the polymer precursor mixture (or a portion of the polymer precursor mixture) at greater than ambient temperature can assist in maintaining solubility of the polymer precursor mixture components, thereby enabling formation of a homogenous mixture.
(79) In an embodiment, the polymer precursor mixture is held at a temperature greater than ambient temperature during free radical polymerization. In an embodiment, the polymer precursor mixture is held a temperature between 65 C. and 150 C. or from 65 C. and 100 C. during the polymerization step. In an embodiment, a pre-cure step is performed in a vacuum environment. In separate embodiments, the curing step is performed using free radical, anionic, cationic, Diels-alder, thiol-ene, polycondensation, or other mechanisms known in the art. During molding, pressure may be applied during polymerization to ensure mold filling.
(80) In an embodiment, an additional curing or heat treatment step is employed after the polymerization step (e.g. after photopolymerization). In an embodiment, the cured parts are removed from the mold and then undergo additional curing operations through exposure to elevated temperatures. In an embodiment, the curing temperature is from 50 C. and 150 C. and the curing time from 5 seconds to 60 minutes during this additional step.
(81) In different embodiments, the amount of functional group conversion is at least 30%, 40%, 50%, 60%, 70%, 80% or 90% or higher. In an embodiment, the amount of extractables is less than or equal to 1% or less than or equal to 0.5%. In an embodiment, the amount of extractables is less than or equal to 5%. In an embodiment, the amount of extractables is less than or equal to 3%. In an embodiment, the amount of extractables is less than or equal to 2%. In an embodiment, the amount of extractables is determined by isopropanol extraction.
(82) As used herein, a crystalline material displays long range order. The crystallinity of polymers is characterized by their degree of crystallinity, or weight or volume fraction of crystalline material in the sample ranging from zero for a completely non-crystalline polymer to one for a theoretical completely crystalline polymer.
(83) If a polymer is semicrystalline, shape change can be hindered and slowed, and performance of devices incorporating the polymer can become clinically unacceptable. In an embodiment, the polymer compositions of the invention are considered substantially amorphous. As used herein, substantially amorphous is defined as the absence of crystalline features as detected by differential scanning calorimetry (DSC), or by inconsistency and lack of reproducibility in mechanical tensile test results, e.g. stress-strain curve at a fixed temperature. In an embodiment, lack of reproducibility may be indicated by reproducibility of less than 95% at 95% confidence interval. A substantially amorphous polymer may incorporate relatively small amounts of crystallinity. As is typical of amorphous polymers, the substantially amorphous polymer compositions of the invention show a transition from a glassy state to a rubbery state over a glass transition temperature range. Crystallinity can be reduced or eliminated by reducing the concentration of specific monomers that enhance this condition, and/or by introducing dissimilar structures to ensure that the polymer's molecular structure doesn't align during polymerization to result in crystallinity.
(84) In an embodiment, the monomers and oligomers (including crosslinker monomers or oligomers) used to form the radiopaque polymer are selected to assure compatibility (e.g. homogeneity after polymerization). In an embodiment, the radiopaque polymer is sufficiently homogenous in terms of solid-phase compatibility of the polymerized units and in the sufficiently random incorporation of units throughout polymerization to obtain the desired performance characteristics. Phase incompatibility can lead to voids in the SMP morphology. Voids in the SMP matrix compromise mechanical performance and can lead to uptake of water and other fluids that displace the generated void volume, even when the incompatible phases are hydrophobic or even water-repellant. Excessively non-random incorporation of comonomers, especially diacrylate or other polyacrylate crosslinkers, as polymerization proceeds from low conversion to high conversion can lead to a non-uniform crosslink density, with regions of higher (brittle) and lower (rubbery) crosslink density.
(85) In an embodiment, the radiopaque polymer is homogenous enough that repeatable results (95% reproducible data at 95% confidence interval) can be obtained in a simple ultimate tensile test at a fixed temperature. In an embodiment, homogeneity of the polymer may be improved by selection of the components of the monomer solution to reduce phase separation in the liquid or solid state. In addition, the monomer components and polymerization technique may be selected to facilitate random incorporation of monomer and crosslinker groups by free radical polymerization during the cure. In an embodiment, the same type of polymerizable groups is present in each of the monomers. For example, for monomers and ologimers (and crosslinker monomers) having acrylate polymerizable groups and aliphatic hydrocarbon linkers, the inductive effect exerted upon the acrylate group by the typically aliphatic linker attachments is expected to be similar.
(86) In many applications, biodurability can be defined as durability for the period of time necessary to assure that the body has overcome the need of the device's function, e.g. a fallopian tube occlusion device that relies upon scar tissue formation to close the lumen no longer needs the device to generate scar tissue once the lumen is fully closed. If that period of time is 90 days, for example, then the biodurable life of the device can be this value plus a suitable safety factor used in the design. Biodurability then is the ability of the device, and its material, to withstand the environmental challenges at its location of placement in the body, e.g. if in the bloodstream, it must withstand a bloody environment. In an embodiment, the radiopaque polymer is not biodegradable within the desired lifetime of the medical device. In another embodiment, the radiopaque polymer is not biodegradable within three years. In an embodiment, the non-biodegradable polymer does not include aromatic groups other than those present in naturally occurring amino acid. In an embodiment, the non-biodegradable polymer does not contain esters that are readily hydrolyzed at physiological pH and temperature.
(87) For almost all locations within the body, one of the several primary mechanisms of degradation can be caused by absorption of water or moisture. Whether the environment contains interstitial fluids, blood, saliva, urine, bile, intracranial fluid, etc., these environments are aqueous based. If the device or its material absorbs water, the material properties and device dimensions can change due to swelling, or the device function can be affected, such as the autogenesis of an errant electrical path, or the material properties can degrade causing the device to weaken or break apart. Therefore a primary consideration for biodurability of an implanted device is the device and all of its material's ability to not absorb water.
(88) In an embodiment, water uptake, or water absorption, can change the device's characteristics or detrimentally affect the device's performance over its intended life. In an embodiment, medical devices fabricated from the polymers of the invention will exhibit minimal water uptake. The water uptake can be measured over a test period equivalent to the lifetime or the device or can be measured over a shorter screening period. In an embodiment, the extent of water uptake is <1% by weight over 24 hours. For devices which exhibit water uptake of greater than 1% by weight over 24 hours, typically continuous exposure results in material changes such as brittleness and eventual mechanical failure in standard testing.
(89) The minimal level of iodine concentration needed to achieve sufficient radiopacity to provide clinically acceptable imaging may be determined empirically. In an embodiment, evaluation of identically sized devices formulated from polymers using different weight percentages of iodinated monomer can be compared under simulated clinical use conditions. Using physicians' subjective review and correlating their opinion with the results from an image analysis program, Image J, to quantify signal levels, clinically imaging quality is correlated with iodine concentration. The result is a determination of the minimum iodine concentration to assure acceptable image quality. In an embodiment, the minimum iodine concentration value was established at 511 mg/cm.sup.3. In an embodiment, the minimum iodine concentration value is above 200 mg/cm.sup.3. In an embodiment, the iodine concentration value is between 50 and 600 mg/cm.sup.3. As is recognized in the art, the radiopaque atom incorporation range for suitable visualization is dependent on the configuration of the device. In an embodiment, the first repeating unit contains the radiopaque atom(s) and is present in an amount of above 15 wt % of the network. In an embodiment, the first repeating unit contains the radiopaque atom(s) and is present in an amount of above 20 wt % of the network. In an embodiment, the first repeating unit contains the radiopaque atom(s) and is present in an amount of above 30 wt % of the network. In an embodiment, any incorporation of radiopaque moieties that produces a functional product can be used. As described elsewhere, the radiopaque atom(s) can include atoms other than iodine, including bromine or bismuth.
(90) In another embodiment, the signal obtained from a radiopaque polymer device may be compared with that of a platinum device of similar dimensions. In an embodiment where signal level is obtained by X-ray under a 6 inch water phantom, the signal from the radiopaque polymer device may be 70%-90% or 80%-90% of that of the platinum device.
(91) Any polymer that can recover an original shape from a temporary shape by application of a stimulus such as temperature is considered a SMP. The original shape is set by processing and the temporary shape is set by thermo-mechanical deformation. A SMP has the ability to recover large deformation upon heating. Shape memory functionality can be utilized to develop medical devices that can be introduced into the body in a less invasive form, wherein the pre-deployed, or temporary, shape is intentionally smaller, or thinner, resulting in a lower profile and a smaller opening (smaller catheter or incision) to introduce the device into the patient than would otherwise be required without the shape change functionality. Then, when stimulated by temperature, typically body temperature but can also be greater than body temperature, the device undergoes shape recovery to return to its permanent, larger form.
(92) A polymer is a SMP if the original shape of the polymer is recovered by heating it above a shape recovery temperature, or deformation temperature (T.sub.d), even if the original molded shape of the polymer is destroyed mechanically at a lower temperature than T.sub.d, or if the memorized shape is recoverable by application of another stimulus. Any polymer that can recover an original shape from a temporary shape by application of a stimulus such as temperature may be considered a SMP.
(93) From a biomedical device perspective, there are characteristics that are considered favorable in device design. They are quantified in terms of stimuli (such as temperature) driven response, well-defined response temperature, modulus, and elongation. In an embodiment, the thermomechanical properties of the shape memory polymer used to form the device are optimized for one or more of the following: Rubbery modulus (Erub), Glass transition temperature (Tg), and Speed of recovery (S).
(94) The preferred ranges of rubbery modulus can be different for different applications. The range of moduli of biological tissue can vary from 20 GPa (bone) to 1 kPa (eye) In an embodiment, the rubbery modulus is between 0.1 MPa and 15 MPa at 37 C. In an embodiment, the rubbery modulus is between 0.1 MPa and 50 MPa for the flexible state and between 0.1 to 500 MPa for the rigid state at 37 C. Any rubbery modulus value that produces a functional product can be used. By polymer formulation adjustments, the SMP's modulus, e.g. stiffness, can be established as very soft, on the order of 0.1 MPa. In one embodiment, for use as a device such as an embolic coil, this soft material enhances compaction of the coil pack, shortening the resulting pack for easier placement and ultimately increasing the speed of occlusion. Through other formulations, a higher value can be achieved for the SMP's modulus, such as 15 MPa, to enhance stiffness. In another embodiment, stiffer SMPs can be used to form a tube stent wherein localized stiffness is used to generate outward radial force against a vessel wall when deployed which is required for retention.
(95) In an embodiment, the polymers are selected based on the desired glass transition temperature(s) (if at least one segment is amorphous) taking into consideration the environment of use. In one method, the polymer transition temperature is tailored to allow recovery at the body temperature, T.sub.rT.sub.g37 C. (A. Lendlein and R. Langer, Biodegradable, elastic shape-memory polymers for potential biomedical applications. Science, vol. 296, pp. 1673-1676, 2002). The distinct advantage of this approach is the utilization of the body's thermal energy to naturally activate the material. The disadvantage of this approach, for some applications, is that the mechanical properties (e.g., stiffness) of the material are strongly dependent on T.sub.g, and can be difficult to alter in the device design process. In particular, it would be difficult to design an extremely stiff device when the polymer T.sub.g is close to the body temperature due to the compliant nature of the polymer. Another possible disadvantage is that the required storage temperature, T.sub.s, of a shape memory polymer with T.sub.g37 C. will typically be below room temperature requiring cold storage prior to deployment. In different embodiments, the glass transition temperature of the SMP of the present invention as determined from the peak of tan is 75 C., 50 C., 45 C. or any useful temperature. In general, as low a glass transition temperature is best, as understood in the art with the desired applications. In different embodiments, the glass transition temperature may be below body temperature (e.g. 25-35 C.), near body temperature (32-42 C.) or above body temperature (40-50 C.). Any Tg value that produces a functional product can be used.
(96) The storage modulus of at least partially non-crystalline polymers decreases in the glass transition region. DMA results highlight the changes that occur as the material is heated from its storage temperature (T.sub.s)) to its response temperature (T.sub.r) and above. Methods are known in the art to determine relevant values to describe SMPs including thermal mechanical analysis (TMA) and differential scanning calorimetry (DSC); TMA and DSC are heating rate dependent. Such methods are described for example in WO 2012/019145, hereby incorporated by reference.
(97) Typically, for each medical device application that incorporates shape recovery, the clinician is anticipating relatively rapid and repeatable shape recovery. In an embodiment, the shape memory polymer devices of the invention produce shape recovery that is fast enough to be detected, completes in a reasonable (intraoperative) time, and repeatable from one device to another. In an embodiment, the shape recovery time can be measured in use or from a screening procedure. The shape recovery time can be measured either from release to 100% recovery or from release to a predetermined amount of recovery.
(98) The rate of shape change correlates with the rate of storage modulus change on the DMA curve between the operating temperature and T.sub.r. For SMPs, rate of shape change can be primarily affected by the temperature difference between T.sub.o, the operating temperature (external heating or body core temperature if self actuated), and the polymer's T.sub.g (derived from the formulation). T.sub.o is typically set above T.sub.r. Typically, a larger difference between these temperatures will produce a faster rate of change up to an inherent rate limit, or asymptote of the change rate, of the material and device. This limit can be identified by monitoring shape change response time at different temperatures and plotting this relationship. Typically, the amount of response time decreases until it reaches an asymptote. The corresponding T.sub.o reflects the lowest, optimum temperature for the fastest rate of shape change for that material. Increasing the temperature above this point does not induce further reductions in the shape change recover time, e.g. does not further increase the rate of shape change. In an embodiment this inherent limit, or asymptote begins when T.sub.o is set at the temperature at which the Tan Delta curve is about 60% of its maximum value. In an embodiment, the polymer's maximum rate of shape change occurs at an environmental operating temperature (To) that is coincident with the temperature above Tg at which the material's Tan Delta value is equal to 60% of its peak value. The device may be designed so that this optimum temperature is at a useful operating temperature for the device (e.g. at body temperature or another preselected temperature).
(99) In an embodiment, the device is operated at a temperature which is the lowest temperature at which no further increase in shape change rate is seen. In another embodiment, the device is operated at a temperature which is within +/5 C. of this optimum temperature.
(100) In different embodiments, the recovery ratio of the SMPs employed in the biomedical devices of the invention is greater than 75%, 80%, 90%, 95%, from 80-100%, from 90-100%, or from 95-100%. In various embodiments, the maximum achievable strain is of the radiopaque SMP from 10% to 800%, from 10% to 200%, from 10% to 500%, from 10% to 100%, from 20% to 800%, from 20% to 500%, from 20% to 800%. as measured at a temperature above the glass transition temperature. In different embodiments, the maximum achievable strain or strain to failure of the radiopaque SMP is at least 30% at least 40%, at least 50%, at least 60%, or at least 70%, from 40% to 100%, from 40% to 60%, from 50% to 100%, from 60% to 100% as measured below the glass transition temperature. In different embodiments, the maximum achievable strain or strain to failure of the SMP is at least 30% at least 40%, at least 50%, at least 60%, or at least 70%, from 40% to 100%, from 40% to 60%, from 50% to 100%, from 60% to 100% as measured at ambient temperature (20-25 C.).
(101) In general, the ability of the device (whether technically shape memory or not) to change conformation or configuration (e.g. to expand) is made possible by manufacturing a device having a first conformation or configuration (initial configuration) and, thereafter configuring the device into a second conformation or configuration (temporary or storage configuration), wherein this configuration is at least partially reversible upon the occurrence of a triggering event. After the triggering event, the device assumes a third configuration. In an embodiment, the third configuration (deployed configuration) is substantially similar to the first configuration. However, for an implanted medical device, the device may be constrained from assuming its initial shape (first configuration). In an embodiment, the device is capable of self-expansion to the desired dimensions under physiological conditions.
(102) The invention can provide a variety of radiopaque polymer devices for medical applications, these devices incorporating the polymer compositions of the invention. In different embodiments, these devices can be for purposes of an indwelling, permanent implant to provide the function of: opening, or maintaining an open anatomical lumen; closing an anatomical lumen, either partially as a valve, or complete lumen occlusion for any physiological fluid or gas flow or for a applied therapeutic fluid or gas flow; support of an anatomical structure to assist in therapeutic restoration of an organ, vascular, digestive, excrement, or airway function; support of an anatomical structure to assist in therapeutic restoration of an orthopaedic, maxillofacial, spinal, joint or other skeletal or function; to support hemostasis by covering an area inside the body after tissue dissection or resection, a patch, such as for hemostasis of the liver, or other organ, In other embodiments, these devices can be used for purposes of a diagnostic or therapeutic instrument or device to provide the function of: a catheter for the purposes of accessing an anatomical location; delivering another device and/or therapeutic agent; or controlling the access or delivery of another device and/or therapeutic agent; a temporarily indwelling device to provide a limited time therapeutic benefit, such as a vena cava filter that is placed in a vessel, left indwelling for a period of time, for example to capture blood clots, and subsequently removed when the therapeutic period is completed.
(103) In one embodiment for neurovascular cases, wherein intracranial aneurysms are repaired, current state of care may use very fine metal (platinum) based embolic coils delivered into the aneurysm sack to fill this space and effect an isolation of the weakened vessel wall from the parent vessel thereby reducing the risk of rupture and stroke. However, because of the metal nature of these devices, two deficiencies typically occur: 1. Approximately 25% of these patients must return for retreatment as the aneurysm continues to grow, and 2. To diagnose the need for retreatment, many of these patients must have an invasive angiogram (contrast injection) of the aneurysm area under fluoroscopy to be able to visualize the condition given that the metal coil materials are not compatible with MRI or CT Scan imaging modalities. A non-metallic, radiopaque SMP embolic device for aneurysm repair does not suffer this limitation in imaging capability.
(104) Although the description herein contains many specificities, these should not be construed as limiting the scope of the invention but as merely providing illustrations of some of the presently preferred embodiments of the invention. For example, thus the scope of the invention should be determined by the appended claims and their equivalents, rather than by the examples given. If any variable is not defined, the variable takes any definition that will allow the group or moiety to be synthesized and function in the desired way, as determined by one of ordinary skill in the art by the context and other information provided herein.
(105) All references throughout this application, for example patent documents including issued or granted patents or equivalents; patent application publications; and non-patent literature documents or other source material; are hereby incorporated by reference herein in their entireties, as though individually incorporated by reference, to the extent each reference is at least partially not inconsistent with the disclosure in this application (for example, a reference that is partially inconsistent is incorporated by reference except for the partially inconsistent portion of the reference).
(106) All patents and publications mentioned in the specification are indicative of the levels of skill of those skilled in the art to which the invention pertains. References cited herein are incorporated by reference herein in their entirety to indicate the state of the art, in some cases as of their filing date, and it is intended that this information can be employed herein, if needed, to exclude (for example, to disclaim) specific embodiments that are in the prior art. For example, when a compound is claimed, it should be understood that compounds known in the prior art, including certain compounds disclosed in the references disclosed herein (particularly in referenced patent documents), are not intended to be included in the claim.
(107) When a compound or composition is claimed, it should be understood that compounds or compositions known in the art including the compounds or compositions disclosed in the references disclosed herein are not intended to be included. When a Markush group or other grouping is used herein, all individual members of the group and all combinations and subcombinations possible of the group are intended to be individually included in the disclosure.
(108) In the moieties and groups described herein, it is understood that the valence form of the group that is required to fulfill its purpose in the description or structure is included, even if not specifically listed. For example, a group that is technically a closed shell group as listed or described can be used as a substituent in a structure, as used herein. For every closed shell moiety or group, it is understood that a group corresponding to a non-closed structural moiety is included, for use in a structure or formula disclosed herein.
(109) Every formulation or combination of components described or exemplified can be used to practice the invention, unless otherwise stated. Specific names of compounds are intended to be exemplary, as it is known that one of ordinary skill in the art can name the same compounds differently. When a compound is described herein such that a particular isomer or enantiomer of the compound is not specified, for example, in a formula or in a chemical name, that description is intended to include each isomers and enantiomer of the compound described individual or in any combination. One of ordinary skill in the art will appreciate that methods, device elements, starting materials, and synthetic methods, and other than those specifically exemplified can be employed in the practice of the invention without resort to undue experimentation. All art-known functional equivalents, of any such methods, device elements, starting materials, and synthetic methods are intended to be included in this invention. Whenever a range is given in the specification, for example, a temperature range, a time range, a composition range or a mechanical property range, all intermediate ranges and subranges, as well as all individual values included in the ranges given are intended to be included in the disclosure.
(110) As used herein, comprising is synonymous with including, containing, or characterized by, and is inclusive or open-ended and does not exclude additional, unrecited elements or method steps. As used herein, consisting of excludes any element, step, or ingredient not specified in the claim element. As used herein, consisting essentially of does not exclude materials or steps that do not materially affect the basic and novel characteristics of the claim. Any recitation herein of the term comprising, particularly in a description of components of a composition or in a description of elements of a device, is understood to encompass those compositions and methods consisting essentially of and consisting of the recited components or elements. The invention illustratively described herein suitably may be practiced in the absence of any element or elements, limitation or limitations which is not specifically disclosed herein.
(111) The terms and expressions which have been employed are used as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the invention claimed. Thus, it should be understood that although the present invention has been specifically disclosed by preferred embodiments and optional features, modification and variation of the concepts herein disclosed may be resorted to by those skilled in the art, and that such modifications and variations are considered to be within the scope of this invention as defined by the appended claims.
(112) In general the terms and phrases used herein have their art-recognized meaning, which can be found by reference to standard texts, journal references and contexts known to those skilled in the art. The preceding definitions are provided to clarify their specific use in the context of the invention.
(113) The invention may be further understood by the following non-limiting examples.
EXAMPLES
Example 1. Polymer Formation
(114) Methods for making polymer compositions are known in the art, including as described in WO2012/019145, incorporated by reference.
Example 2. Formation of Clustered Crosslinkers
(115) Shown below is an exemplary synthesis of a clustered pentaerythritol triacrylate (Sartomer SR444, Sartomer USA) with spacer:
(116) ##STR00029##
(117)
(118)
(119)
Example 3. Formation of Iodinated Monomers with Spacers
(120) The synthesis of structures such as the first monomer having different chain length between the polymerizable group and iodinated ring can be performed as described herein and known in the art. As a specific example, the structure
(121) ##STR00030##
can be synthesized by the following exemplary procedure.
(122) Set-up a 500 mL multi-neck flask in a water bath with mechanical agitator, thermocouple, nitrogen purge, and condenser vented to the basic solution scrubber. Charge 70 g 2,3,5-triiodobenzoic acid (TIBA) to the flask. Then charge 30 g thionyl chloride and Charge 300 g dichloromethane to the flask. Heat the pot to reflux at 40 C. with vigorous mixing. Hold for 20 hours at temperature. There should be very little solids remaining if TIBA is converted. Distill away most of the dichloromethane at atmospheric pressure, then add 100 g toluene to the flask and vacuum to distill away the remaining thionyl chloride, allowing flask temperature to reach 55-60 C. When no longer condensing thionyl chloride, add 100 g toluene and pull a maximum vacuum of 25 in. Hg. Stop distilling when the head temperature is above 45 C. for at least 30 minutes. Charge 58 g toluene, 21 g pyridine, and 32.5 g 2-hydroxyethyl acrylate (2-HEA) to a 1 L addition funnel. Switch to air sparge and heat flask to 30 C. Begin the addition of the 2-HEA solution. The addition should take about 45 minutes and the flask temperature should be kept below 50 C. After the addition, increase the flask temperature to 45-50 C. and maintain for 1 hour. Cool the flask to room temperature and decant the product solution. Filter product solution with 1 micron filter paper to clear. Wash the product consecutively, retaining the organic layer each time, with 140 g of 3.6% hydrochloric acid solution, then with 140 g of 6.6% potassium carbonate solution, then with 140 g deionized water. Filter the organic layer with 1 micron filter paper. Place the filtered organic layer back into a clean 500 mL flask and remove toluene by heating flask to maximum temperature of 60 C and pull vacuum to strip toluene. Distill toluene until it the system is 30-35% solids. Cool the flask to room temperature. Weigh the solution. Heat the solution to about 50 C. so that it is completely dissolved. Slowly add hexane to precipitate the product. The amount of hexane should total 1.5 times the product solution weight. Chill the solution to about 5 C.
(123) The structure below can be made by the following exemplary synthetic method:
(124) ##STR00031##
(125) A solution of 6-bromohexanol (15 g) in anhydrous THF (85 mL) was stirred under nitrogen in a methanol/ice bath. Triethylamine (12 mL) was added slowly and the solution became cloudy. Acryloyl chloride (7.1 mL) in anhydrous THF (35 mL) was then added dropwise. The milky suspension was then warmed slowly to room temperature and stirred for 30 minutes, whereupon the reaction was judged complete by TLC (KMnO.sub.4 stain). A small aliquot was removed and after small workup was analyzed by NMR to confirm completion. The reaction mixture was then diluted with methyl tert-butyl ether (MTBE) and water and the mixture partitioned. The MTBE layer was then washed successively with water three times and then with brine, and then dried with anhydrous magnesium sulfate filtered, and evaporated to afford 11.6 g of pure product. Product identity was confirmed by .sup.1H-NMR and .sup.13C-NMR. Purity was >95% by NMR. A flask containing compound 1 (11.6 g), 2,3,5-triiodobenzoic acid (TIBA; 35 g), potassium carbonate (13.5 g), and anhydrous DMF (250 mL) was heated to 85 C. under nitrogen for 90 minutes. The reaction was judged complete by TLC (KMnO.sub.4 stain). The reaction mixture was cooled to room temperature and then in an ice bath for 15 minutes. To the cooled flask was added water (500 mL) and the product was extracted into MTBE (2500 mL). The combined MTBE extracts were washed successively with water (4500 mL) and brine (500 mL) and then dried with anhydrous magnesium sulfate, filtered, and evaporated to afford an oil which solidified upon standing. Yield: 24.2 g (73%). The product was judged >97% pure by .sup.1H NMR. Product identity was confirmed by .sup.1H-NMR and .sup.13C-NMR.
Example 4. Synthesis of C8-TIA
(126) A multi-neck flask was flushed with nitrogen and charged with 8-bromo-1-octanol (30 g) as a liquid via pipet. THF (180 mL) was added to the flask via syringe and the mixture was stirred with a magnetic stir bar. The flask was cooled in an ice/methanol bath. Triethylamine (21 mL) was added via syringe and the mixture turned cloudy. Acryloyl chloride (12.3 mL) was dissolved in THF (30 mL) and added slowly to the mixture via an addition funnel. The reaction mixture turned into a milky white suspension. After the addition was complete, the cold bath was removed and the mixture was allowed to warm to RT and stirred for 1 hour. The mixture was diluted with methyl tert-butyl ether (MTBE) and washed with water three times. The organic layer was dried over MgSO.sub.4, filtered, and concentrated in vacuo to a neat liquid. The material was dried briefly under high vacuum to give 8-bromooctyl-acrylate (20.7 g, 55% yield) as a lightly colored liquid. The product was charged as a liquid via pipet into a multi-neck flask that had been flushed with nitrogen. DMF (400 mL) was poured into the flask and the mixture was stirred with a magnetic stir bar. 2,3,5-Triiodobenzoic acid (55.1 g) was added as a solid and the mixture turned darker in color. Potassium carbonate (21.8 g) was added as a solid and the reaction mixture was heated with a heating mantle to 85 C. for 2.5 hours. A small aliquot was worked up and analyzed by NMR to determine that the reaction was complete. The reaction was cooled to ambient temperature and diluted with water. The mixture was extracted with MTBE four times until TLC confirmed that almost no product remained in the aqueous layer. The combined organics were washed with water three times followed by a brine wash. The layer was dried with anhydrous MgSO.sub.4, filtered, and concentrated to an oil. The oil was allowed to sit (in darkness) overnight during which time some of it precipitated into a white solid. A mixture of 10% ethyl acetate in heptane was added to dissolve the oil and triturate the solid. The solid was isolated in a Buchner funnel and dried under high vacuum to give about 8 grams of product. The filtrate was concentrated and re-dissolved in hot pentane with a minimal amount of MTBE added to get the material to dissolve. The mixture was allowed to cool slowly to ambient temperature and then the flask was placed in a freezer for 1 hour. A white solid precipitated during this time. The cold suspension was briefly sonicated to precipitate more material. The solid was collected on a Buchner funnel, rinsed with a small amount of pentane, and dried under high vacuum to give 12.5 grams of product that was checked by NMR. The filtrate was concentrated to give about 20 grams of product as an oil. The material was dissolved in DCM and adsorbed onto silica gel. The material was purified via silica gel vacuum chromatography using 0% to 5% to 10% ethyl acetate in heptane as eluent. The fractions containing the product spot were isolated and concentrated in vacuo to give an oil. The oil was dissolved in hot pentane with a minimal amount of MTBE to dissolve the material. The flask was allowed to slowly cool to RT and then stored in a freezer overnight. More solid had precipitated during this time. The solid was collected on a Buchner funnel, rinsed with a minimal amount of pentane, and dried under high vacuum to give 14 g of product that was checked by NMR. All of the batches were combined to give 35 g (66% yield) of 2,3,5-Triiodobenzoic acid-8-acryloyloxy-octyl ester as a white solid. The product was characterized by .sup.1H NMR, .sup.13C NMR, LC-MS, and melting point analysis.
Example 5. Synthesis of 6XLE Crosslinker
(127) Charge pentaerythritol triacrylate (19.97 g) to a pressure-equalizing addition funnel fitted with a Drie-Rite drying tube and add anhydrous pyridine (3.0 mL), then dissolve both to 100 mL in the funnel with anhydrous dichloromethane. In a 1000 mL 3-neck round-bottom flask, dissolve sebacoyl chloride (3.99 g) to 500 mL with anhydrous dichloromethane. While stirring the sebacoyl chloride solution, add the pentaerythritol triacrylate-pyridine solution at an average rate of 2.5 mL/min, keeping the exotherm below 26 C. At the end of the addition, reflux the system for 2 hours, then extract sequentially with 175 mL quantities of 0.5N HCl, 0.5 M Na.sub.2CO.sub.3 and distilled water. Dry the organic phase with 10 g anhydrous magnesium sulfate and filter through fluted filter paper into 1000 mL round-bottom flask. Remove excess dichloromethane on rotary evaporator; transfer solution into 50 mL round-bottom flask and finish solvent removal on rotary evaporator. Add a magnetic stir bar to the 50 mL round-bottom flask and sparge with nitrogen for 3 hours while stirring the viscous solution magnetically. Add acetone (3.0 mL), distilled water (1.0 mL) and pyridine (3.0 mL) to the 50 mL flask and stir at 50 C. for 1 hour. Extract solution sequentially with 175 mL quantities of 0.5N HCl, 0.5 M Na.sub.2CO.sub.3 and distilled water. Dry the organic phase with 10 g anhydrous magnesium sulfate and filter through fluted filter paper into 1000 mL round-bottom flask. Remove excess dichloromethane on rotary evaporator; transfer solution into 50 mL round-bottom flask and finish solvent removal on rotary evaporator. Add a magnetic stir bar to the 50 mL round-bottom flask and sparge with nitrogen for 3 hours while stirring the viscous solution magnetically. Remove stir bar from flask; yield 16.7 g (73%).
Example 6. Synthesis of PC-2110H
(128) Charge to a 1000 mL 3-neck flask fitted with a Drie-Rite drying tube 50 g poly(hexamethylene carbonate) diol (MW 2,000), 250 mL anhydrous dichloromethane, and 8.3 mL triethylamine. Stir with a magnetic stir bar until homogeneous. Add 4.5 mL acryloyl chloride in two portions of 2.0 mL and 2.5 mL, keeping exotherm below 34 C. Reflux system in flask for 2 hours, then extract with 175 mL quantities of 0.1N HCl, 0.1M Na.sub.2CO.sub.3 and saturated NaCl in distilled water. Dry the organic phase with 10 g anhydrous magnesium sulfate and filter through fluted filter paper into 1000 mL round-bottom flask. Remove excess dichloromethane on rotary evaporator; transfer solution into 250 mL round-bottom flask and finish solvent removal on rotary evaporator. Add a magnetic stir bar to the 250 mL round-bottom flask and sparge with nitrogen for 3 hours while stirring the solution magnetically with the flask immersed in a 60 C. water bath to prevent the crosslinker from solidifying. Yield: 46 g.
Example 7. SMP with 6XLE and PC-2110H Crosslinker
(129) A 5 mL vial was charged with C8-TIA (3.50 g), 6XLE (0.90 g) and PC-2110H (0.60 g). The vial contents were melted and mixed to form a homogeneous melt. Then Luperox P (30 L) was added, mixed into the melt thoroughly, and the mixture was injected into a DMA specimen mold and cured at 125 C. for two hours. DMA results (
Example 8. Synthesis of Poly(tetrahydrofuran)-diacrylate (MW 1,110; pTHF-1 K)
(130) To a 1000 mL 3-neck flask with a Drie-Rite drying tube add 100 g poly(tetrahydrofuran) diol (MW 1,000), 400 mL anhydrous dichloromethane, and 31 mL triethylamine. Stir with a magnetic stir bar until homogeneous. Dissolve 17 mL acryloyl chloride to 100 mL with anhydrous dichloromethane in a pressure-equalizing addition funnel. Add the acryloyl chloride solution to the stirring flask contents while keeping the exotherm temperature below 30 C. Reflux system in flask for 2 hours, then extract with 250 mL quantities of 0.1N HCl, 0.1 M Na.sub.2CO.sub.3 and saturated NaCl in distilled water. Dry the organic phase with 10 g anhydrous magnesium sulfate and filter through fluted filter paper into 1000 mL round-bottom flask. Remove excess dichloromethane on rotary evaporator; transfer solution into 250 mL round-bottom flask and finish solvent removal on rotary evaporator. Add a magnetic stir bar to the 250 mL round-bottom flask and sparge with nitrogen for 3 hours while stirring the solution magnetically with the flask immersed in a 60 C. water bath to prevent the crosslinker from solidifying. Yield: 92 g.
Example 9. SMP with Sartomer CN2302, SR399 and pTHF-1 K Crosslinkers
(131) A 5 mL vial was charged with a 1:1 w:w mixture of C11-TIA and C12-TIA (4.0 g), Sartomer CN2302 (0.50 g), Sartomer SR399 (0.40 g), and pTHF-1 K (0.10 g). Sartomer CN2302 is described by the manufacturer as a hyperbranched polyester acrylate. SR 399 is described as dipentaertyritol pentaacrylate. The components were melted at 125 C. and a vacuum was applied to remove entrapped air in the system. Then Luperox P (30 L) was added, mixed thoroughly, and the molten mixture was injected into a DMA specimen mold and cured at 125 C. for two hours. DMA results (
Example 10. Synthesis of 6-Hydroxyhexyl-acrylate (HHA)
(132) A multi-neck flask was flushed with nitrogen and charged with 6-bromo-1-octanol (26 g). The product was charged as a liquid via pipet into a multi-neck flask that had been flushed with nitrogen. DMF (400 mL) was poured into the flask and the mixture was stirred with a magnetic stir bar. 2,3,5-Triiodobenzoic acid (71.8 g) was added as a solid and the mixture turned darker in color. Potassium carbonate (19.8 g) was added as a solid and the reaction mixture was heated with a heating mantle to 85 C. for 2.5 hours. A small aliquot was worked up and analyzed by NMR to determine that the reaction was complete.
Example 11. Exemplary Radiopaque Polymer Device
(133) Shape memory polymer devices of the invention can incorporate material formulations that utilize a suitable glass transition temperature within a range about body core temperature. To achieve different performance requirements, the polymer's T.sub.g may be intentionally suppressed below body temperature resulting in shape change occurrence immediately upon release from any physical constriction.
(134) Non-metallic Radiopaque polymers provide a significant clinical benefit in providing good visibility of the device using common imaging techniques such as fluoroscopy, CAT-scan, and MRI. However, the material's non-metallic nature uniquely enables imaging without the typical generation of an imaging artifact, in both Cat-Scan and MRI modalities, common with metal based devices that obscures the physician's ability to view key anatomy.
(135) In one embodiment, a radiopaque SMP with a T.sub.g of 25 C. has been utilized to accelerate the rate of shape change of an embolic coil upon expulsion from a small lumen catheter. One form of embolic devices forms a large curl of 10 mm in diameter but is constructed of an SMP wire that is only 0.032 in diameter. The wire can be formed into a pre-deployed curled shape that is straightened to allow delivery of these devices in a small diameter catheter (<5 fr). When deployed into the blood stream, these devices recovered their curl shape to effectively occlude a 9 mm vessel, with the 1 mm oversize assuring sufficient radial force from the material modulus and deflection to provide effective anchoring so that the embolic device doesn't migrate under the influence of blood flow in the vessel. A variety of coil shapes, coil diameters, curl shapes and curl diameters can leverage this capability.
(136) Likewise, the polymer's Tg may be set above body temperature wherein an external heating device is used to provide the physician with a discretionary shape change function. In another embodiment, an SMP with a T.sub.g of 50 C. has been used to place and accurately position a tube stent within an anatomical lumen. Maintaining its low profile, predeployed temporary shape benefits the physician's ability to move and accurately locate the device prior to deployment. When held in the desired position, the device is heated to its T.sub.r by flushing with warmed saline irrigation which causes shape recovery to occur to the stent's permanent shape.
(137) Yet, another embodiment is the use of an SMP with an elevated T.sub.g of 42 C. (just above body core temperature) that is used as a clasp for retaining a deployed device. In its permanent shape, the clasp is open, in its temporary shape, the clasp is closed. The clasp connects a device, such as a vena cava filter, the filter itself may be made from a different SMP, to a delivery guidewire that contains electrical conductors joined to a heating element adjacent to the clasp. With the SMP clasp closed in its temporary shape (below T.sub.g), the device is advanced into the bloodstream. Upon reaching its desired position, the clasp is heated through an external low voltage passing down the conductors and through the heating element. Upon the temperature reaching T.sub.r, the clasp opens to its recovered, permanent shape, releasing the vena cava filter.
(138) In an embodiment, an SMP with an elevated T.sub.g of 42 C. (just above body core temperature) is used within a section of a mono-directional catheter. The catheter section is formed with a permanent curved shape to allow specific direction of the tip of the catheter. As a straight catheter is easier to manipulate into position, the temporary shape is straight but not necessarily stiff. Upon entry into the body, below T.sub.g, the straight catheter is easily manipulated to a target location wherein it is warmed by an externally heated, internal delivery wire, or by warmed saline solution flushed through the catheter. Upon the material temperature reaching T.sub.r, the catheter section curls, returning to its recovered, permanent shape, providing specific direction for the catheter tip during use. Meanwhile, the curvature is not so stiff as to preclude simply retrieving the catheter after use.