Aqueous ATRP in the presence of an activator regenerator
09982070 ยท 2018-05-29
Assignee
Inventors
- Krzysztof Matyjaszewski (Pittsburgh, PA)
- Pawel Chmielarz (Pittsburgh, PA, US)
- Dominik Konkolewicz (West Chester, OH, US)
- Pawel Krys (Pittsburgh, PA, US)
- Xiangcheng Pan (Pittsburgh, PA, US)
- Valerie Williams (Pittsburgh, PA, US)
Cpc classification
C08F4/50
CHEMISTRY; METALLURGY
C08F2438/01
CHEMISTRY; METALLURGY
C08F120/28
CHEMISTRY; METALLURGY
International classification
C08F220/54
CHEMISTRY; METALLURGY
C08F120/28
CHEMISTRY; METALLURGY
Abstract
A process for polymerizing radically (co)polymerizable monomers at a temperature between 10 C. and 110 C. in an aqueous system comprising one or more radically (co)polymerizable monomer(s) is disclosed, and includes a molar excess of a ligand forming a soluble transition metal complex with an added transition metal salt that participates in a reversible reduction-oxidation cycle with one of an added site specific functional initiator and a dormant polymer chain having a radically transferable atom or group. The initial soluble catalyst complex concentration in the higher oxidation state is less than or equal to 2500 ppm. The reaction is conducted in the presence of an activator regenerator. The mole fraction of the soluble lower activator oxidation state transition metal formed by action of the activator regenerator, to transition metal in a higher deactivator oxidation state is less than 10%. The formed polymer chains have a dispersity of less than 1.5.
Claims
1. An atom transfer radical polymerization (ATRP) process comprising: polymerizing one or more soluble radically (co)polymerizable monomer(s) in the presence of an aqueous polymerization medium, wherein the aqueous polymerization medium comprises: a molar excess of a ligand compared to a concentration of transition metal salt; wherein the transition metal salt interacts with the ligand to form a stable soluble transition metal complex; wherein the stable soluble transition metal complex participates in a reversible reduction-oxidation cycle with an added functional ATRP initiator that comprises one or more radically transferable atoms or groups and a dormant polymer chain, which also comprises a radically transferable atom or group; wherein the polymerizing occurs at a temperature in a range of about 10 C. to 110 C. in the presence of an aqueous system comprising a concentration of the stable soluble transition metal complex in a higher oxidation state of less than or equal to 2500 ppm; wherein the polymerizing is carried out in the presence of an activator regenerator, the amount of which is selected to only reduce less than 10% mole fraction of the stable soluble transition metal complex in a higher oxidation state to a stable soluble transition metal complex in a lower activator oxidation state by in situ reduction through reaction with the activator regenerator; wherein polymer chains formed by the polymerizing have a predetermined molecular weight and a polydispersity, Mw/Mn, of less than 1.25; and wherein the activator regenerator comprises a photochemical procedure.
2. The process of claim 1, wherein the activator regenerator further comprises an electrochemical procedure.
3. The process of claim 1, wherein the aqueous polymerization medium comprises greater than 50% by weight water.
4. The process of claim 1, wherein the added transition metal salt has the same counterion as the stable soluble transition metal complex.
5. The process of claim 1, wherein the added transition metal salt has a different counterion to that initially present on the stable soluble transition metal complex thereby allowing a halogen exchange reaction to occur when the added functional ATRP initiator is a (macro)initiator.
6. The process of claim 1, wherein the mole fraction of the stable soluble transition metal complex in a lower activator oxidation state to stable soluble transition metal transition metal complex in a higher oxidation state is less than 5%.
7. The process of claim 6, wherein the mole fraction of the stable soluble transition metal complex in a lower activator oxidation state to stable soluble transition metal complex in a higher oxidation state is less than 2%.
8. The process of claim 1, wherein the molar ratio of the ligand to transition metal salt is greater than 1:2.
9. The process of claim 1, wherein the temperature is in a range of 0 C. to 50 C.
10. The process of claim 9, wherein the concentration of the stable soluble transition metal complex in a higher oxidation state is less than 1000 ppm.
11. The process of claim 9, wherein the concentration of the stable soluble transition metal complex in a higher oxidation state is less than 600 ppm.
12. The process of claim 1, wherein the concentration of the stable soluble transition metal complex in a higher oxidation state is less than 1000 ppm.
13. The process of claim 1, wherein the concentration of the stable soluble transition metal complex in a higher oxidation state is less than 600 ppm.
14. The process of claim 1 conducted with ppm levels of the transition metal salt, a salt comprising a (pseudo) halide counterion, and one or more pieces of a zero-valent transition metal in contact with the reaction medium as a readily removable solid; wherein the concentration of initial the stable soluble transition metal complex in a higher oxidation state is less than 1000 ppm.
15. The process of claim 14, wherein the concentration of the stable soluble transition metal complex in a higher oxidation state is less than 600 ppm.
16. The process of claim 14, wherein the concentration of stable soluble transition metal complex in a higher oxidation state is less than 250 ppm.
17. The process of claim 14, wherein the concentration of stable soluble transition metal complex in a higher oxidation state is less than 100 ppm.
18. The process of claim 14, wherein the aqueous polymerization medium comprises greater than 75% by weight water.
19. The process of claim 14, wherein the stable soluble transition metal complex comprises one or more of copper or iron.
20. The process of claim 14, wherein the temperature is in a range of 0 C. to 50 C.
21. An atom transfer radical polymerization (ATRP) process comprising: polymerizing one or more soluble radically (co)polymerizable monomer(s) in the presence of an aqueous polymerization medium, wherein the aqueous polymerization medium comprises: a molar excess of a ligand compared to a concentration of transition metal salt; wherein the transition metal salt interacts with the ligand to form a stable soluble transition metal complex; wherein the stable soluble transition metal complex participates in a reversible reduction-oxidation cycle with an functional ATRP initiator that comprises one or more radically transferable atoms or groups and a dormant polymer chain, which also comprises a radically transferable atom or group; wherein the polymerizing occurs at a temperature in a range of about 10 C. to 110 C. in the presence of an aqueous system comprising a concentration of the stable soluble transition metal complex in a higher oxidation state of less than or equal to 2500 ppm; wherein the polymerizing is carried out in the presence of an activator regenerator, the amount of which is selected to only reduce less than 10% mole fraction of the stable soluble transition metal complex in a higher oxidation state to a soluble transition metal complex in a lower activator oxidation state by in situ reduction through reaction with the activator regenerator; wherein polymer chains formed by the polymerizing have a predetermined molecular weight and a polydispersity, Mw/Mn, of less than 1.25; and wherein the activator regenerator comprises silver.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) Various features and characteristics of the non-limiting and non-exhaustive embodiments disclosed and described in this specification may be better understood by reference to the accompanying figures, in which:
(2)
(3)
(4)
(5) 3(b) Evolution of [Cu.sup.II] in activation experiments under the conditions: [OEOBrP].sub.0=20 mM, [Me.sub.6TREN].sub.0=40 mM, 18 wt % OEOA in water, in V=4.5 mL at 22 C. with different lengths of Cu.sup.0 wire. Inset of
(6) 3(c) Evolution of [Cu.sup.II] in activation experiments under the conditions: [OEOBrP].sub.0=20 mM, 18 wt % OEOA in water, 10 cm Cu.sup.0 wire (d=1 mm) in V=4.5 mL at 22 C. with different [Me.sub.6TREN].sub.0;
(7)
(8) (a) in water or in 18 wt % OEOA in water;
(9) (b) in water in the absence and presence of OEOBrP;
(10) (c) in 18 wt % OEOA in water in the absence and presence of OEOBrP; determination of k.sub.a1 for the reaction of Cu.sup.I/Me.sub.6TREN.sup.+ with
(11) (d) HEBiB in 18 wt % OEOA in water;
(12) (e) OEOBrP in pure water; and
(13) (f) OEOBrP in 18 wt % OEOA in water, by fitting of the experimental data on theoretical working curves at 25 C.;
(14)
(15)
(16)
(17)
(18)
(19)
(20) (b) Conversion of Cu.sup.II to Cu.sup.I under comproportionation under the conditions: [Cu.sup.IIBr.sub.2].sub.0=2.5 mM, [Me.sub.6TREN].sub.0=20 mM, 18 wt % OEOA in water, in V=4.5 mL at 22 C. with different lengths of Cu.sup.0 wire. Inset of
(21) (c) Conversion of Cu.sup.II to Cu.sup.I under comproportionation under the conditions: [Cu.sup.IIBr.sub.2].sub.0=2.5 mM, [Me.sub.6TREN].sub.0=20 mM, 18 wt % OEOA in water, 10 cm Cu.sup.0 wire (d=1 mm) in V=4.5 mL at 22 C. with different [Me.sub.6TREN].sub.0;
(22)
(23) (b) concentration of all species vs. monomer conversion; and
(24) (c) reaction rates vs. monomer conversion for polymerization under the conditions [OEOA].sub.0:[HEBiB].sub.0:[Cu.sup.IIBr.sub.2].sub.0:[Me.sub.6TREN].sub.0=100:1:0.01:0.2, [OEOA]=0.41 M, 10 cm of Cu.sup.0 wire (d=1 mm) in V=6 mL with 30 mM of NaBr added at 22 C. Here R.sub.p is the propagation rate, R.sub.a1 is the rate of alkyl halide activation by Cu.sup.I, R.sub.d1 is the rate of radical deactivation by Cu.sup.II, R.sub.a0 is the rate of alkyl halide activation by Cu.sup.0, R.sub.t is the rate of termination, R.sub.comp is the rate of comproportionation, R.sub.disp is the rate of disproportionation, and R.sub.d0 is the rate of radical deactivation by Cu.sup.I;
(25)
(26) (b) concentrations of all species vs. monomer conversion; and
(27) (c) reaction rates vs. monomer conversion for polymerization under the conditions [OEOA].sub.0:[HEBiB].sub.0:[Cu.sup.IIBr.sub.2].sub.0:[Me.sub.6TREN].sub.0=100:1:0.01:0.2, [OEOA]=0.41 M, 10 cm of Cu.sup.0 wire (d=1 mm) in V=6 mL with no NaBr added at 22 C. Here R.sub.p is the propagation rate, R.sub.a1 is the rate of alkyl halide activation by Cu.sup.I, R.sub.d1 is the rate of radical deactivation by Cu.sup.II, R.sub.a0 is the rate of alkyl halide activation by Cu.sup.0, R.sub.t is the rate of termination, R.sub.comp is the rate of comproportionation, R.sub.disp is the rate of disproportionation, and R.sub.d0 is the rate of radical deactivation by Cu.sup.I;
(28)
(29) (a) Evolution of conversion vs. time;
(30) (b) evolution of M.sub.n and M.sub.w/M.sub.n with conversion;
(31)
(32) (b) concentrations of all species vs monomer conversion; (c) reaction rates vs monomer conversion and for polymerization under the conditions [OEOA].sub.0:[HEBiB].sub.0:[Cu.sup.IIBr.sub.2].sub.0:[Me.sub.6TREN].sub.0=100:1:0.01:0.2, [OEOA]=0.41 M, 10 cm of Cu.sup.0 wire (d=1 mm) in V=6 mL with no NaBr added at 22 C. and with K.sub.Br.sup.II=10.sup.6.1 M.sup.1;
(33)
(34) (b) Evolution of [Cu.sup.II] vs time for model reaction between Cu.sup.0 wire (d=1 mm, l=10 cm) and 20 mM OEOBrP in the presence of 20 mM Me.sub.6TREN in 4.5 mL of H.sub.2O at room temperature, giving k.sub.a0.sup.app=410.sup.6 cm s.sup.1.
(35)
(36) (a) First-order kinetic plot of monomer conversion versus time; and
(37) (b) M.sub.n and M.sub.w/M.sub.n versus monomer conversion;
(38)
(39)
(40)
(41)
(42) (b) Semilogarithmic kinetic plots for photo-on/off polymerization under conditions [OEOMA].sub.0/[PEOBPA].sub.0/[CuBr.sub.2].sub.0/[TPMA].sub.0=200/1/0.1/0.4 with 5 mM NaBr in 90% water under 392 nm irradiation (0.9 mW/cm.sup.2); and
(43) (c) UV-Vis spectra for the mixtures [OEOMA.sub.500].sub.0/[PEOBPA].sub.0/[CuBr.sub.2].sub.0/[TPMA].sub.0=450/1/9/36 or [OEOMA.sub.500].sub.0/[PEOBPA].sub.0/[CuBr.sub.2].sub.0/[TPMA].sub.0=450/1/3/12 in 90% water.
DESCRIPTION
(44) The reader will appreciate the foregoing details, as well as others, upon considering the following detailed description of various non-limiting and non-exhaustive embodiments according to the present disclosure.
(45) Various embodiments are described and illustrated in this specification to provide an overall understanding of the structure, function, operation, manufacture, and use of the disclosed processes and products. It is understood that the various embodiments described and illustrated in this specification are non-limiting and non-exhaustive. Thus, the invention is not limited by the description of the various non-limiting and non-exhaustive embodiments disclosed in this specification. Rather, the invention is defined solely by the claims. The features and characteristics illustrated and/or described in connection with various embodiments may be combined with the features and characteristics of other embodiments. Such modifications and variations are intended to be included within the scope of this specification. As such, the claims may be amended to recite any features or characteristics expressly or inherently described in, or otherwise expressly or inherently supported by, this specification. Further, Applicant reserves the right to amend the claims to affirmatively disclaim features or characteristics that may be present in the prior art. Therefore, any such amendments comply with the requirements of 35 U.S.C. 112, first paragraph, and 35 U.S.C. 132(a). The various embodiments disclosed and described in this specification can comprise, consist of, or consist essentially of the features and characteristics as variously described herein. The initial activator regenerator used to determine the exact mechanism of activator regeneration ATRP was modeled by an added or in situ formed copper zero metal which acts as both a supplemental activator and reducing agent for the added or formed transition metal complex in the higher oxidation state. Subsequently it was determined that the mechanism clarified by this specific examination of the kinetics of the procedure can be applied to other activator regeneration procedures.
(46) Any patent, publication, or other disclosure material that is said to be incorporated, in whole or in part, by reference herein is incorporated herein only to the extent that the incorporated material does not conflict with existing definitions, statements, or other disclosure material set forth in this disclosure. As such, and to the extent necessary, the disclosure as set forth herein supersedes any conflicting material incorporated herein by reference. Any material, or portion thereof, that is said to be incorporated by reference herein, but which conflicts with existing definitions, statements, or other disclosure material set forth herein is only incorporated to the extent that no conflict arises between that incorporated material and the existing disclosure material.
(47) In this specification, other than where otherwise indicated, all numerical parameters are to be understood as being prefaced and modified in all instances by the term about, in which the numerical parameters possess the inherent variability characteristic of the underlying measurement techniques used to determine the numerical value of the parameter. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter described in the present description should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.
(48) Also, any numerical range recited in this specification is intended to include all sub-ranges of the same numerical precision subsumed within the recited range. For example, a range of 1.0 to 10.0 is intended to include all sub-ranges between (and including) the recited minimum value of 1.0 and the recited maximum value of 10.0, that is, having a minimum value equal to or greater than 1.0 and a maximum value equal to or less than 10.0, such as, for example, 2.4 to 7.6. Any maximum numerical limitation recited in this specification is intended to include all lower numerical limitations subsumed therein and any minimum numerical limitation recited in this specification is intended to include all higher numerical limitations subsumed therein. Accordingly, Applicant reserves the right to amend this specification, including the claims, to expressly recite any sub-range subsumed within the ranges expressly recited herein. All such ranges are intended to be inherently described in this specification such that amending to expressly recite any such sub-ranges would comply with the requirements of 35 U.S.C. 112, first paragraph, and 35 U.S.C. 132(a). Additionally, as used herein when referring to compositional elemental ranges, the term up to includes zero unless the particular element is present as an unavoidable impurity.
(49) The grammatical articles one, a, an, and the, as used in this specification, are intended to include at least one or one or more, unless otherwise indicated. Thus, the articles are used in this specification to refer to one or more than one (i.e., to at least one) of the grammatical objects of the article. By way of example, a component means one or more components, and thus, possibly, more than one component is contemplated and may be employed or used in an implementation of the described embodiments. Further, the use of a singular noun includes the plural, and the use of a plural noun includes the singular, unless the context of the usage requires otherwise.
(50) While the present disclosure was to some degree motivated by the excellent control attained in polymerization conducted in water with high concentrations of added catalyst complex, which claimed that the kinetics were governed by the activation of the alkyl halide by Cu.sup.0 and ongoing research within CMU on the role of Cu.sup.0 in an ATRP reaction [Macromolecules, 2013, 46, 3803-27.] which indicated that Cu.sup.I was the main activator and Cu.sup.0 a supplemental activator and a reducing agent, the objective of the research program detailed herein was to determine if it was possible that an ATRP could be conducted in water with low ppm levels of catalyst.
(51) This required a complete analysis, quantification and simulation of the kinetics of all contributing reactions and determination of the equilibrium position of the comproportionation/disproportionation reactions in aqueous media in the presence on monomers which should also take into account the kinetics of competitive reactions.
(52) ##STR00002##
(53) Guided by these detailed in depth mechanistic studies, simulations of the reaction conditions were developed that surprisingly allowed reaction conditions to be designed to give well-controlled polymerizations with 600 ppm of Cu.sup.II in the initial polymerization solution where the polymerization was conducted in the presence of a very low concentrations of Cu.sup.I that are generated and maintained in the modelled aqueous reaction medium by the presence of an easily removable sample of Cu.sup.0.
(54) After generating this detailed analysis of the polymerization procedure the knowledge indicated that it should be possible to conduct the supplemental activation and/or activator regeneration procedure with other transition metals in the zero oxidation state or in the presence of a chemical capable of participating in a reduction reaction such as inorganic sulfites, or alternatively by a potentiometric eATRP [PCT/US11/65578], or through a photo-induced reduction reaction [paper submitted for publication] each of which would also allow simple procedures for purification of the final polymer.
(55) A series of model experiments were designed to elucidate and subsequently define the mechanism of an ATRP conducted in the presence of a transition metal complex, in this exemplary case the most commonly utilized transition metal for an ATRP copper, when the polymerization is conducted in water as a solvent to specifically determine whether (i) activation of dormant alkyl halides was faster by Cu.sup.I or Cu.sup.0 species, and (ii) whether activation of alkyl halides by Cu.sup.I was faster than Cu.sup.I disproportionation. Except for certain specific model controlled disproportionation and comproportionation experiments which were carried out in pure water, all actual polymerization experiments were performed in a mixture of 18 wt % oligo(ethylene oxide) monomethyl ether acrylate (M.sub.n=480) (OEOA) in water. This mixture was selected as an exemplary polymerization medium as it represents a commonly used polymerization medium consisting predominantly of water, but also because 10-20% of monomers such as NIPAM or OEOA have been employed for preparation of biocompatible conjugated materials [WO 2013/028756] and it is an additional exemplification of a procedure to prepare a copolymer for bio-applications. Indeed poly(N-isopropylacrylamide) (PNIPAM) is widely used in cosmetics, for biomedical applications, wastewater treatment, and oil recovery. [Prog. Polym. Sci. 2011, 36 (11), 1558-1628; J Am Chem Soc 2013, 135 (19), 7355-7363.]
(56) However, successful ATRP of acrylamides and its derivatives is especially challenging with respect to the level of control of the polymerization when using water as the solvent. ATRP of NIPAM has a relatively low value for its ATRP equilibrium constant (K.sub.ATRP) and displays some potential side reactions that include ligand displacement from the copper catalyst by the formed polymers, and loss of chain-end halogen (CX) by solvolysis. [Macromol. 2012, 45 (10), 4015-4039] Since the XCu.sup.II/L bond can easily dissociate in aqueous media, typically either high concentrations of catalyst are needed, or the presence of additional salts with halide anions is required. [Macromol. 2004, 37 (26), 9768-9778; Macromol. 2014, 47 (2), 560-570.] Hydrolysis of alkyl halides in water can be suppressed by conducting the polymerizations at lower temperatures. [ACS Symposium Series 2009, 1023, 127-137; Macromol Rapid Comm 2014, 35 (10), 965-970.] The best disclosed control over an ATRP of (meth)acrylamides was obtained using one of the most active catalytic systems, Cu.sup.IBr/Me.sub.6TREN, due to its intrinsically high values for K.sub.ATRP. [Macromol. 1998, 31 (17), 5958-5959.] PNIPAM with narrow MWD (M.sub.w/M.sub.n=1.08) was prepared by employing a water soluble initiator, however high catalyst loadings (ca. 10,000-15,000 ppm) were used. Recently another procedure for synthesis of PNIPAM with narrow MWD (M.sub.w/M.sub.n=1.13-1.22) was reported, but it required a large amount of organic solvent, at least 50%. [J Polym Sci Pol Chem 2010, 48 (8), 1752-1763; J Polym Sci Pol Phys 2014, 52 (7), 507-516.] While NIPAM copolymers with poly(ethylene oxide) were reported, the polymerizations either took long time (24 h) to reach high conversion and yielded polymers with broad MWD (M.sub.w/M.sub.n=1.45-1.51), [Polymer 2005, 46 (9), 2836-2840] or required the use of high amounts of organic (co)solvent, [Soft Matter 2012, 8 (37), 9526-9528.] or high amounts of catalyst. [Adv Mater 2006, 18 (21), 2905.] Therefore polymerization conditions for N-isopropylacrylamide really needed to be examined and optimized to provide for fast reactions in aqueous media employing low catalyst concentrations, while maintaining narrow molecular weight distributions and high retention of chain end functionality.
(57)
(58) Since Cu.sup.I complexes absorb strongly below 450 nm these spectra show that within 30 s of adding HEBiB, an ATRP initiator, all the Cu.sup.I is converted to Cu.sup.II. Finally, the Cu.sup.II concentration increases continuously with time, and eventually stabilizes after 30 min at an absorbance of ca. 0.9. This indicates that during this time there is also slow consumption of the precipitate attributed to Cu.sup.0 and there was much less precipitate present in the reaction medium 20 min after the addition of HEBiB and the solution was a light blue color, which is typical of Cu.sup.II complexes in water. The absorbance of ca. 0.9 corresponds to 2 mM Cu.sup.II, hence the absorbance of ca. 0.3 before the addition of HEBiB corresponds to ca. 0.7 mM Cu.sup.II. When one considers the disproportionation stoichiometry, this indicates that 0.7 mM of Cu.sup.I was converted to Cu.sup.0, but the remaining Cu in the reaction medium must be Cu.sup.I, giving a remaining soluble Cu.sup.I concentration of ca. 0.6 mM and ca. 9 mM of uncoordinated ligand.
(59) The disproportionation reaction and apparent equilibrium constants are:
(60)
(61) Here, the term apparent is used to describe the equilibrium constant or rate coefficient based only on the total concentration of Cu in each oxidation state, without reference to specific associations between ligands, halides and the metal.
(62) The concentrations measured in the above example give an apparent equilibrium constant for disproportionation of approximately 20, which will be shown to be consistent with other model experiments.
(63) The Cu.sup.II concentration, [Cu.sup.II], essentially doubled after the addition of HEBiB whereas before adding HEBiB, [Cu.sup.I]=[Cu.sup.II]. The doubling of [Cu.sup.II] after adding HEBiB demonstrated that Cu.sup.I reacted very rapidly with HEBiB, generating radicals that underwent rapid radical/radical termination reactions, causing the rapid accumulation of Cu.sup.II. The second slow increase of Cu.sup.II, corresponds to slow activation of the remaining HEBiB by Cu.sup.0 forming Cu.sup.I which also underwent rapid radical/radical termination reactions. The three stages of Cu.sup.II evolution are shown in
(64) The equilibrium constants, and measured rate coefficients, are the apparent ones, based on the total Cu.sup.I, and Cu.sup.II species in solution, while neglecting specific associations between the metal centers, ligands and halides. [Macromol. 2010, 43, 9257-67] This is particularly important in water, since halides can partially dissociate from the Cu.sup.II species, leading to poor deactivation efficiency. [Macromol. 2012, 45, 4461-4468]
(65) This process and the equilibrium constant are shown below:
(66)
where Cu.sup.II/L.sup.++ is a Cu.sup.II complex with ligand only, and Cu.sup.IIBr/L.sup.+ is a Cu.sup.II complex coordinated by both a ligand and halide that can act as a deactivator. This association constant is K.sub.Br.sup.II=4.4 M.sup.1 for BrCu.sup.II/Me.sub.6TREN in water but ca. 10.sup.5M.sup.1 in other solvents.
(67) An experiment similar to that shown in
(68) Model reactions were performed (similar to those reported in the literature that were carried out in DMSO, [Macromol. 2013, 46, 3793-3802 and 3803-3815]) to characterize the aqueous system more precisely. First, the activation of alkyl halides by Cu.sup.0 was studied. A secondary alkyl halide initiator oligo(ethylene oxide) 2-bromopropionate (OEOBrP) was synthesized to mimic the chain end of poly(OEOA)-Br.
(69) Activation experiments were performed with [Me.sub.6TREN]=20 mM, [OEOBrP]=20 mM, and different lengths of the same diameter Cu.sup.0 wire. The results are reported in
(70)
(71)
where [RX] is the alkyl halide concentration, and the superscript app refers to the fact that total Cu.sup.0 surface area, and concentrations of all Cu.sup.I and Cu.sup.II were used, without reference to specific association/speciation. This equation was applied to all the data shown in
(72) These results are unexpected and establish that, contrary to literature contentions about the activity of Cu.sup.0 formed by disproportionation, [Percec, V.; et al.; J. Am. Chem. Soc. 2006, 128, 14156-14165] Cu.sup.0 is a very slow activator of alkyl halides in aqueous media, in correlation to low stability and high reactivity of the resulting Cu.sup.I species.
(73) In order to define conditions that allowed for ppm level of catalyst in a well-controlled aqueous ATRP it was also necessary to evaluate the activation rate of alkyl halides by Cu.sup.I, and compare the value to that determined for activation by Cu.sup.0. The rate coefficients k.sub.a1 and k.sub.a0 cannot be directly compared because they have different units (one is a homogeneous reaction and the other a heterogeneous reaction). Due to concurrent disproportionation in these aqueous systems, it was not possible to directly measure the Cu.sup.I activation rate coefficient using stopped flow techniques but fortunately activation rate coefficients can also be determined using electrochemical techniques. [J. Am. Chem. Soc., 2011, 133 11944-47] The homogeneous redox catalysis approach of C. Andrieux et. al., [J. Electroanal. Chem. 1978, 87, 55-65; J. Electroanal. Chem. 1978, 87, 39-53; and J. Electroanal. Chem. 1980, 113, 19-40.] was employed in these measurements as they have been widely applied to the determination of rate coefficients of activation reactions between alkyl halides and various catalysts including both outer-sphere and inner-sphere reducing agents.
(74)
(75) This behavior is typical of electrochemical processes involving a catalytic cycle in which the electroactive species is rapidly regenerated near the electrode. The proposed reaction mechanism for the catalytic activation of RX by Cu.sup.I/L.sup.+ is shown in Scheme 3, where L stands for Me.sub.6TREN.
(76) ##STR00003##
(77) The proposed electrocatalytic mechanism involves two redox steps, one for Cu.sup.II/L.sup.++ and one for the ternary complex Cu.sup.IIX/L.sup.+. Although in non-aqueous solvents, the standard reduction potential of Cu.sup.IIX/L.sup.+ is more negative than that of Cu.sup.II/L.sup.2+ and two distinct reversible peak couples can be observed in cyclic voltammetry, [Macromol. 2009, 42, 6348-60 and 2010, 43, 9257-67] in this series of experiments only one reduction peak was observed, indicating that E.sub.Cu.sub.
(78) The rate coefficient of the activation reaction can be calculated by examining the catalytic current enhancement or degree of catalysis defined as I.sub.p,c/I.sub.p,d, where I.sub.p,c and I.sub.p,d stand for the cathodic peak current of the catalyst measured in the presence and absence of initiator, respectively. The degree of catalysis strongly depends on the rate coefficient of the activation reaction as well as on the scan rate and an excess factor expressing the ratio between the concentrations of initiator and catalyst, =C.sub.RX/C.sub.Cu.sub.
(79) Theoretical working curves relating I.sub.p,c/I.sub.p,d with a kinetic parameter =RTk.sub.a1C.sub.Cu.sub.
(80)
(81) The result of this analysis is highlighted in
(82) The very high activity of Cu.sup.I would explain why essentially all the Cu.sup.I was rapidly converted to Cu.sup.II after adding HEBiB as shown in
(83) The high activity of the Cu complexes in aqueous media is confirmed in
(84) The activation rate of 10 mM of OEOBrP is:
R.sub.a0=k.sub.a0.sup.appS/V[OEOBrP]=6.310.sup.8Ms.sup.1(6)
but, in order to have R.sub.a0=R.sub.a1, the required concentration of Cu.sup.I needed to match the rates is:
[Cu.sup.I/Me.sub.6TREN]=R.sub.a1/(k.sub.a1.sup.app[OEOBrP])=2.510.sup.10M(7)
given that the typical Cu.sup.I concentration is in the order of 1 M this indicates that Cu.sup.I has a much higher activity than Cu.sup.0 in aqueous media. Another way of stating the difference in activity, (for k.sub.a0=110.sup.5 and k.sub.a1=2.510.sup.4) is that it would require 400 m of Cu.sup.0 wire with diameter 1 mm in 5 mL of 18 wt % OEOA in water to match reactivity of 1 M Cu.sup.I/Me.sub.6TREN which would indicate that the predominant activator is Cu.sup.I.
(85) In order to gain a full understanding of the mechanism it was also important to determine the kinetics of comproportionation, and disproportionation, see Scheme 2. Preferentially this can be done by studying the kinetics of comproportionation, to avoid the formation of large quantities of Cu.sup.0 precipitate that can scatter light and disrupt a UV-Vis experiment during a disproportionation. As shown in the literature, there was almost complete disproportionation of the Cu.sup.IBr/Me.sub.6TREN complex in pure water. [J. Am. Chem. Soc., 2013, 135, 7355-7363]. This was confirmed in our studies and is reported in
(86) However, once again, contrary to the results reported, and confirmed, for pure water, it was unexpectedly determined that in the presence of only 18 wt % OEOA monomer in water, the Cu.sup.IIBr.sub.2/Me.sub.6TREN complex underwent a certain degree of comproportionation with added solid Cu.sup.0. Typically, ca. 15% of the initial Cu.sup.II was converted to Cu.sup.I.
(87) The surface area dependence of the comproportionation reaction was confirmed by using 3 different lengths of Cu.sup.0 wire.
(88) The effect of [Me.sub.6TREN].sub.0 on the kinetics and equilibrium of comproportionation was also investigated.
(89) As outlined in the experimental section, the kinetics and equilibrium position can be used to determine the apparent rate coefficients of comproportionation and disproportionation, in a way similar to that employed for DMSO systems. [Macromol. 2013, 46, 3793-3802.] These values are given in Table 1, with average values of K.sub.disp.sup.L,app=22, k.sub.comp.sup.app=2.410.sup.75 cm s.sup.1, and k.sub.disp.sup.app=510.sup.4 cm s.sup.1.
(90) Kinetic simulations were performed to determine the contribution of each specific reaction to the overall rate of polymerization. These simulations were needed to accurately determine the concentrations of reagents and resulting reaction rates. The results determined from the simulations are shown in
(91)
(92) The next class of significant reactions, occurring 3 orders of magnitude slower than activation by Cu.sup.I are the activation by Cu.sup.0 and termination. Comproportionation is ca. 1 order of magnitude slower than activation of alkyl halides by Cu.sup.0 while disproportionation is 7 orders of magnitude slower than activation of alkyl halides by Cu.sup.I, and radical deactivation by Cu.sup.I is negligible. This is because during the controlled polymerization the concentration of Cu.sup.I is very low (ca. 1 M) due to the very high activity of Cu.sup.I towards activating alkyl halides. This low concentration of Cu.sup.I implies that the rate of disproportionation of Cu.sup.I is low, since the rate of disproportionation is proportional to [Cu.sup.I].sup.2 and therefore disproportionation contributes only slightly to the kinetics of the system, even though it is thermodynamically favored.
(93) This surprising result clearly demonstrates that Cu.sup.I is the major activator, even in strongly disproportionating solvents such as 82% water. Indeed, when less than 2,000 ppm catalyst is added or will be formed, this result indicates that reaction conditions should be selected to generate a low [Cu.sup.I] in order to allow the large excess of Cu.sup.II to be responsible for efficient deactivation and provide control in a reaction medium with very high values for K.sub.ATRP. Furthermore it indicates that a well-controlled ATRP can be conducted in aqueous media comprising a fraction of (co)monomers in the presence of a low concentration/surface area of copper metal, or other reducing agent, or activator regenerator, discussed in incorporated references. Indeed this indicates that while 300 ppm Cu.sup.II was added to the low volume of reagents used in the examples in the presence of copper metal with relatively low surface area as the volume of the reaction medium is increased even lower levels of Cu.sup.II could be employed as it would be simpler to add known amounts of solid copper surfaces to reduce a lower fraction of added Cu.sup.II and maintain an appropriate lower concentration of Cu.sup.I to activate the polymerization and still allow efficient deactivation by Cu.sup.II. The same argument would hold for more polar media such as polymerization of acids.
(94)
(95) One key difference between the system with and without added halide salt is the concentration of the deactivator complex Cu.sup.IIX/L.sup.+. In the system with 30 mM of NaBr, the concentration of Cu.sup.IIX/L.sup.+ is in the order of 0.1 mM,
(96) The importance of considering the low halidophilicity, K.sub.Br.sup.II, in water is confirmed in by comparing the simulations with no added NaBr and K.sub.Br.sup.II=10.sup.2M.sup.1 in
(97) Activation of alkyl halides occurs much faster than disproportionation in both DMSO and in aqueous media, as seen in the simulations reported in
(98) The most important, and surprising, conclusion from the model kinetic studies, polymerizations and simulations, is that although aqueous media does indeed promote both activation of alkyl halides and favorable thermodynamics of Cu.sup.I disproportionation, it is not the thermodynamics of the comproportionation/disproportionation processes that distinguish between supplemental activator and reducing agent (SARA) ATRP and prior art examples claiming single electron transfer living radical polymerization (SET-LRP), but rather the kinetics of the reactions. As disclosed herein the presented studies indicate that even in media containing over 80% water, SARA ATRP correctly describes the mechanism, since Cu.sup.I is the major activator of alkyl halides and activation of the alkyl halide by Cu.sup.I is much faster than Cu.sup.I disproportionation. These results indicate that in aqueous media, Cu.sup.I is a very powerful activator of alkyl halides, Cu.sup.0 is a slow supplemental activator of alkyl halides, and that in the polymerization media some comproportionation of Cu.sup.0 and Cu.sup.II can occur, but at a relatively slow rate, Scheme 4.
(99) Although the rate coefficient for disproportionation was found to be relatively higher than in DMSO, the actual contribution of disproportionation is quite small, due to the very low concentration of Cu.sup.I that is present in a solution which actually provides a controlled polymerization, which is a result of its high activity. This is due to the scaling of alkyl halide activation as the first power of [Cu.sup.I], whereas disproportionation of Cu.sup.I scales as the second power of [Cu.sup.I], i.e. [Cu.sup.I].sup.2. This implies that the high activity of Cu.sup.I drives the concentration of Cu.sup.I to very low values by activating alkyl halides, and leads to low rates of disproportionation since the value of [Cu.sup.I].sup.2 should be even lower.
(100) These results differ from literature conclusions promoted by SET-LRP advocates and agree well with the SARA ATRP mechanism, even in water in the presence of low concentrations of water soluble radically (co)polymerizable monomers, since Cu.sup.0 is a slow activator of alkyl halides and the concentration of Cu.sup.I is very much below the equilibrium concentration required for disproportionation, ca. 10-20%. This is a manifestation of the competitive equilibria phenomenon that applies to various RDRPs, including polymerization in the presence of Cu.sup.0.
(101) In summary it was determined by simulations using equilibrium constants and rate coefficients determined in aqueous media that in a polymerization medium containing 18 wt % OEOA, the rate constant of Cu.sup.I activation of alkyl halides was >10.sup.2 times higher than in DMSO. In the polymerization medium, the concentration of Cu species are defined by the ATRP equilibrium with a very low concentration of very reactive Cu.sup.I species (<1 M) resulting in minimal disproportionation. Model studies showed that comproportionation occurred with the equilibrium favoring disproportionation although both reactions are relatively slow. The kinetic simulations confirm that the high activity of Cu.sup.I towards alkyl halide activation ensures that it is the major activator of alkyl halides. A high concentration of Cu.sup.II is the major deactivator of radicals, and its rate matches that of Cu.sup.I activation, thereby providing a controlled SARA ATRP system.
(102) ##STR00004##
(103) Taking all these unexpected results into consideration polymerizations were performed in aqueous media, confirming that excellent control can be attained in the presence of 600 ppm of soluble Cu.sup.II, and an excess of halide salt. This concentration of soluble Cu.sup.II essentially provides transparent colorless solutions and represents a 15 fold reduction in soluble Cu relative to previous work employing pre-disproportionation of ca. 10,000 ppm Cu.sup.I species in water and provides industrially viable conditions for conducting an ATRP polymerization in water in the absence of additional reducing agents in addition to simplifying purification procedures if they are required for the application.
(104) The procedure employed to determine the kinetics of the reactivation process resulted in the inventors realizing that other activator regenerator procedures they had developed should also work under the conditions defined by this modelling study. Of immediate relevance is that the utilized activator regenerator could be any of the zero valent transition metals disclosed in U.S. Pat. No. 6,541,580, preferentially Cu.sup.0, Fe.sup.0 for specific reduction of Cu.sup.II and Fe.sup.III respectively, while Ag.sup.0 or inorganic sulfites would also be suitable for reduction of Cu.sup.II and Fe.sup.III or any other transition metal selected for the ATRP. [Polymer Chemistry 2013, 4, 5629-5636; J Am Chem Soc 2015, 137, 1428-1431.] The critical requirement is that the amount of activator regenerator should be selected to provide a suitable ratio of Cu.sup.I to Cu.sup.II. This targeted ratio would depend on the polarity of the polymerization medium with the ratio decreasing as the polarity of the reaction medium increases.
(105) The data provided herein makes determining the correct ratio a relatively short simple experimental procedure for a selected set of monomers at different ratios of monomer to water. Polymerization conditions can be optimized to provide for fast reactions, due to the polar nature of the polymerization medium, while employing low concentrations of catalyst.
(106) The fact that the ratio of Cu.sup.I to Cu.sup.II is so low in the successful aqueous SARA ATRP determine above indicated that electrochemically controlled ATRP [Angew. Chem. Int. Ed.; 2011, 50, 11391-11394; Macromolecules 2013, 46, 4346-4353.] could also be conducted in aqueous media if an appropriate applied current was employed to generate a low fraction of Cu.sup.I activator species which is then distributed throughout the reaction medium by vigorous stirring.
(107) Photoinduced ATRP was also successfully performed in aqueous media. Good control was obtained for the polymerization of oligo(ethylene oxide) methyl ether methacrylate (OEOMA) in the presence of CuBr.sub.2 and tris(2-pyridylmethyl)amine (TPMA) ligand when irradiated with a visible light of 392 nm wavelength at 0.9 mW/cm.sup.2 intensity,
(108) ##STR00005##
(109) Linear semilogarithmic kinetic plots and increasing molecular weight with conversion were observed during the polymerization process,
(110) In one embodiment of the invention a controlled ATRP in aqueous media, preferably greater than 50% water, is conducted with the addition of ppm levels of a higher oxidation state transition metal salt in the presence of an excess of a salt comprising a (pseudo) halide counterion and in the presence of an activator regenerator thereby allowing polymerizing radically polymerizable monomers at a temperature of between about 4 C. and 110 C., preferentially between 0 C. and 50 C.
(111) In one embodiment of the invention the controlled polymerization reaction occurs in the presence of an aqueous system comprising a partially soluble transition metal complex that participates in a reversible reduction-oxidation cycle with at least one of a site specific functional initiator and a dormant polymer chain having a radically transferable atom or group, wherein the concentration of the soluble catalyst complex is less than or equal to 2500 ppm, preferentially less than 1000 ppm and more preferentially less than 600 ppm and the reaction is conducted in the presence of a solid transition metal in the zero oxidation state which acts as the activator regenerator wherein the mole fraction of transition metal in a lower, activator oxidation state to transition metal in an higher, deactivator oxidation state is less than 1:10, and in certain conditions of high polarity reaction medium less than 1:100, and a molar excess ligand that forms the soluble complex with the transition metal catalyst wherein the formed polymer chains have a dispersity, or Mw/Mn, of less than 1.5.
(112) The solid transition metal in the zero oxidation state can be present in the reaction medium in a physical state that is easily removed from the reaction during the polymerization to control any undesired exotherm and can be reinserted to the reaction medium after thermal control is reestablished and restart the reaction, and can be easily removed from the final reaction medium after the (co)polymerization reaction is complete.
(113) In one embodiment of the invention SARA ATRP can be carried out in aqueous media with low concentrations of soluble catalyst. The DP of resulting (co)polymers increase linearly with monomer conversion and semilogarithmic kinetic plots are linear.
(114) In one non-limiting example of water soluble monomers the successful formation of the block copolymers confirms the living nature of the SARA ATRP of N-isopropylacrylamide in aqueous media. Thus, conducting SARA ATRP under appropriate conditions, without pre-disproportionation of high concentrations of Cu.sup.I/L complexes, indeed in the presence of low concentrations of Cu species, [Cu.sup.II/L].sub.0= or less than 500 ppm, optionally less than or equal to 300 ppm, is an efficient synthetic route for functional water-soluble derivatives of acrylates and acrylamides with controlled chain lengths, narrow molecular weight distributions and high retention of chain end functionality. The supplemental activator and reducing agent can be a transition metal in zero oxidation state including but not limited to copper, iron and silver in addition to inorganic sulfites.
(115) In another embodiment of the invention the activator regenerator can comprise an external stimulation agent such as an electric current or a photo-stimulated reduction reaction.
EXPERIMENTAL SECTION AND DISCUSSION OF RESULTS
Materials
(116) All chemicals were purchased from commercial suppliers, e.g., Aldrich, TCI, Alfa Aesar and used as received, unless otherwise stated. Tris(2-(dimethylamino)ethyl)amine (Me.sub.6TREN) was synthesized as reported in the literature. Oligo(ethylene oxide) monomethyl ether acrylate of molecular weight 480 (OEOA.sub.480) was passed over a column filled with basic alumina to remove inhibitor prior to use. Metallic copper (Cu.sup.0, diameter 1 mm) was washed with HCl in methanol and subsequently rinsed with methanol and dried under a stream of nitrogen following literature procedures.
(117) Instrumentation.
(118) Gel permeation chromatography (GPC): GPC was used to determine number average molecular weight (M.sub.n) and M.sub.w/M.sub.n values. The GPC was conducted with a Waters 515 HPLC Pump and Waters 2414 Refractive Index Detector using PSS columns (Styrogel 10.sup.2, 10.sup.3, 10.sup.5 ) in tetrahydrofuran (THF) as an eluent at a flow rate of 1 mL/min at 35 C. The column system was calibrated with 12 linear poly(methyl methacrylate) (PMMA, M.sub.n=8002,570,000) standards.
(119) NMR:
(120) Monomer conversion was measured using .sup.1H NMR spectroscopy, using a Bruker Avance 500 MHz spectrometer at room temperature.
(121) UV-Visible Spectroscopy:
(122) All characterizations were performed using an Agilent 8453 UV-Vis Spectrometer.
(123) Electrochemistry:
(124) Cyclic voltammetry was performed with an Autolab PGSTAT30 potentiostat (Eco-Chimie, Utrecht, Netherlands), controlled by a PC through Gpes program. All experiments were carried out in a thermostated three-electrode cell with a glassy carbon (GC) working electrode, a Pt counter-electrode and saturated calomel reference electrode. The supporting electrolyte was 0.1 M tetraethylammonium tetrafluoroborate. 1 mM solutions of [Cu.sup.IIMe.sub.6TREN].sup.2+ in H.sub.2O or 18 wt % OEOA in water were prepared in situ by mixing equimolar amounts of Cu(OTf).sub.2 (OTf=trifluoromethansulfonate) and Me.sub.6TREN in the chosen solvent. The GC electrode was a 3 mm diameter disc embedded in glass, which was fabricated from a GC rod (Tokai, GC-20) and polished to a mirror finish with silicon carbide papers and diamond paste. Before every experiment it was cleaned by polishing with a 0.25 m diamond paste followed by ultrasonic rinsing in ethanol for about 5 minutes.
(125) Digital simulation of cyclic voltammetry was carried out with the program DigiSim 3.03b (Bioanalytical Systems)
(126) Preparation of Stock Solutions:
(127) Water was vigorously bubbled with nitrogen for at least 30 min prior to use and stored in a Schlenk flask. All stock solutions were prepared by adding the solid components to a Schlenk flask, sealing the Schlenk flask, followed by the evacuation and backfilling with nitrogen at least 4 times prior to addition of the liquid components followed by the addition of deoxygenated water.
Example 1 Synthesis of oligo(ethylene oxide) 2-bromopropionate
(128) ##STR00006##
(129) Oligo(ethylene oxide) monomethyl ether with number-averaged molecular weight 550 (6.64 g, 0.012 mol) was added to a flask followed by addition of 150 mL of dichloromethane (DCM) and triethylamine (6.31 g, 0.062 mol) and the reagents were allowed to combine under stirring and the flask and contents cooled to 0 C. Subsequently, 2-bromopropionyl bromide (11.02 g, 0.51 mol) was slowly added and the reaction mixture was stirred at 0 C. for 1 h, followed by stirring at 22 C. for 24 h. The reaction mixture was washed 4 times with 100 mL of dilute hydrochloric acid, followed by 4 washes with a dilute sodium carbonate solution. The majority of the DCM was removed under reduced pressure, and the product was added drop wise to diethyl ether, followed by removal of the volatiles and dissolution of the product in a small amount dichloromethane. The product was precipitated by addition of the solution to hexanes, and the viscous liquid collected and dried under reduced pressure to give oligo(ethylene oxide) monomethyl ether 2-bromopropionate (OEOBrP) (7.23 g, 0.0105 mol, 88% yield). The purity was established to be greater than 96% by NMR.
(130) Experiment Directed at Understanding the Kinetics
(131) Model disproportionation experiment in water: Cu.sup.IBr (1.4 mg, 0.0098 mmol) was added to a Schlenk flask then the flask was sealed with a stopper connected to a cuvette, and evacuated and backfilled with nitrogen 4 times. A second Schlenk flask was sealed with a glass stopper and then briefly evacuated and backfilled with nitrogen 4 times. Me.sub.6TREN (13.8 mg, 0.06 mmol) was added to this flask, followed by deoxygenated water (6 mL). The mixture was homogenized by vigorous shaking. 5 mL of this 10 mM solution of Me.sub.6TREN in water was taken and added with vigorous shaking to the reaction flask containing Cu.sup.IBr. The reaction flask was shaken continuously for 45 min, except when the times when evolution of Cu.sup.IIBr.sub.2 was monitored by UV-Vis-NIR spectroscopy.
(132) Model Disproportionation Experiment and Activation Experiment in OEOA/Water:
(133) Cu.sup.IBr (1.4 mg, 0.0098 mmol) was added to a Schlenk flask then the flask was sealed with a stopper connected to a cuvette, and evacuated and backfilled with nitrogen 4 times. OEOA (1.08 g, 2.25 mmol) was added to a second Schlenk flask which was sealed with a glass stopper and then briefly evacuated in backfilled with nitrogen 4 times. Me.sub.6TREN (13.8 mg, 0.06 mmol) was added to this flask, followed by deoxygenated water (5 mL). The mixture was homogenized by vigorous shaking. 5 mL of this 10 mM Me.sub.6TREN in OEOA/water solution was taken and added with vigorous shaking to the reaction flask containing Cu.sup.IBr. The reaction flask was shaken continuously for 20 min, except when the evolution of Cu.sup.IIBr.sub.2 was monitored by UV-Vis-NIR spectroscopy. Subsequently, 2-hydroxyethyl -bromoisobutyrate (HEBiB) (53 mg, 0.25 mmol) was added and the reaction mixture homogenized, and the UV-Vis-NIR spectrum was measured 30 s after the addition of HEBiB. The flask was then shaken for an additional 30 min, except when UV-Vis-NIR spectrum were being measured.
(134) Model Cu.sup.IBr Activation Experiment in OEOA/Water:
(135) Cu.sup.IBr (1.4 mg, 0.0098 mmol) was added to a Schlenk flask, the flask was sealed with a stopper connected to a cuvette, and evacuated and backfilled with nitrogen 4 times. OEOA (1.08 g, 2.25 mmol) was added to a second Schlenk flask which was sealed with a glass stopper and then briefly evacuated in backfilled with nitrogen 4 times. Me.sub.6TREN (13.8 mg, 0.06 mmol) was added to this flask followed by deoxygenated water (5 mL) and HEBiB (63 mg, 0.30 mmol). The mixture was homogenized by vigorous shaking then 5 mL of this 10 mM Me.sub.6TREN and 50 mM HEBiB in OEOA/water solution was taken and added with vigorous shaking to the flask containing the Cu.sup.IBr. The reaction flask was shaken continuously for 30 min, except when the evolution of Cu.sup.IIBr.sub.2 was monitored by UV-Vis-NIR spectroscopy.
(136) Typical Cu.sup.0 Activation Experiment:
(137) OEOBrP (61.7 mg) and OEOA (0.75 g) were added to a clean Schlenk flask equipped with a magnetic stirrer bar, followed by addition of a piece of Cu.sup.0 wire (length=10 cm, diameter=1 mm). The flask was sealed with a stopper connected to a quartz cuvette, and briefly evacuated and backfilled with nitrogen at least 4 times prior to the addition of deoxygenated water (3.2 mL). The solution was bubbled with nitrogen for 5 min. Finally, 0.5 mL of a deoxygenated stock solution containing 180 mM Me.sub.6TREN was added and the initial UV-Vis spectrum was measured. The kinetics of the formation Cu.sup.IIBr.sub.2/Me.sub.6TREN were measured by UV-Vis spectrometry. Due to the presence of two different Cu.sup.IIBr.sub.2 complexes in the monomer/water solution, a deconvolution of the raw spectrum was needed to determine the total concentration of Cu.sup.II species. This complex Cu.sup.II spectrum was quantitatively solved for the Cu.sup.II, by monitoring the UV-Vis-NIR spectrum for a system with a fixed concentration of Cu.sup.II over time.
(138) Typical Voltammetric Determination of Rate Coefficients for Alkyl Halide Activation by Cu.sup.I:
(139) Cu(OTf).sub.2 (5.43 mg, 15.0 mmol) and Me.sub.6TREN (3.64 mg, 15.8 mmol) were added to an electrochemical cell complete with electrodes and stirring bar, and containing 15 mL of water (or 18 wt % OEOA in water). When the reaction was conducted in the H.sub.2O-OEOA solution a large excess of 2,2,6,6-tetramethyl-1-piperdinyloxy (TEMPO, 150 mmol) was added. After purging the solution with argon a series of voltammograms were recorded at different scan rates in a potential range (0.1-0.7 V) around the redox potential of the copper complex. A certain amount of initiator, chosen to give a fixed value of the excess factor =C.sub.RX/C.sub.[Cu.sub.
(140) Typical Comproportionation Experiment:
(141) OEOA (0.81 g) was added to a clean Schlenk flask equipped with a magnetic stirrer bar followed by addition of the Cu.sup.0 wire (length=10 cm, diameter=1 mm). The flask was sealed with a stopper connected to a quartz cuvette, and briefly evacuated and backfilled with nitrogen at least 4 times. Water (3.2 mL) was then added to this flask and the solution was bubbled with nitrogen for 5 min. Finally, 0.5 mL of an aqueous stock solution containing 22.5 mM Cu.sup.IIBr.sub.2 and 180 mM Me.sub.6TREN was added and the initial sample was measured by UV-Vis spectrometry. The disappearance of Cu.sup.IIBr.sub.2/Me.sub.6TREN over time was measured by UV-Vis spectrometry. Due to the presence of two different Cu.sup.IIBr.sub.2 complexes in the monomer/water solution, a deconvolution of the raw spectrum was needed to determine the total concentration of Cu.sup.II species.
(142) Typical Polymerization Experiment, with Initial Addition of Cu.sup.IIBr.sub.2:
(143) OEOA.sub.480 (1.10 g, 2.29 mmol) was added to a clean Schlenk flask equipped with a magnetic stirrer bar. The flask was sealed with a glass stopper, or a stopper connected to a quartz cuvette, and briefly evacuated and backfilled with nitrogen at least 4 times. Deoxygenated water (4.5 mL) previous bubbled with nitrogen for 60 min, 70 L of a deoxygenated stock solution containing 66 mM Me.sub.6TREN, Cu.sup.0 (length=10 cm, diameter=1 mm), 20 L of a deoxygenated stock solution containing 12 mM Cu.sup.IIBr.sub.2 and NaBr (18.5 mg, 0.181 mmol) were then added to this flask. Finally, the mixture was bubbled with nitrogen for another 10 min and 0.4 mL of a deoxygenated stock solution containing 57 mM HEBiB was added. The kinetics of polymerization was measured by taking small samples periodically from the reaction mixture. Additionally, in one experiment the evolution of Cu.sup.IIBr.sub.2 over time was monitored by UV-Vis-NIR spectroscopy. Due to the presence of two different Cu.sup.IIBr.sub.2 complexes in the monomer/water solution, a deconvolution of the raw spectrum was needed to determine the total concentration of Cu.sup.II species.
(144) Typical Polymerization Experiment, without Initial Addition of Cu.sup.IIBr.sub.2:
(145) OEOA.sub.480 (1.10 g, 2.29 mmol) was added to a clean Schlenk flask equipped with a magnetic stirrer bar. The flask was sealed with a glass stopper, and briefly evacuated and backfilled with nitrogen at least 4 times then deoxygenated water (4.1 mL) previous bubbled with nitrogen for 60 min, 0.4 mL of a deoxygenated stock solution containing 11.4 mM Me.sub.6TREN, a piece of Cu.sup.0 wire (length=10 cm, diameter=1 mm) and NaBr (18.5 mg, 0.181 mmol) were added. Finally, the mixture was bubbled with nitrogen for another 10 min and 0.5 mL of a deoxygenated stock solution containing 45.7 mM HEBiB was added. The kinetics of polymerization was measured by taking small samples from the reaction mixture.
(146) Additional Characterization
(147) Evolution of Cu Concentration, as Measured by UV-Vis-NIR Spectroscopy:
(148) The UV-Vis-NIR spectrum was measured in a polymerization experiment, as a function of time for polymerization reactions under the conditions: [OEOA].sub.0:[HEBiB].sub.0:[Cu.sup.IIBr.sub.2].sub.0:[Me.sub.6TREN].sub.0=100:1:0.01:0.2, [OEOA]=0.41 M, 10 cm of Cu.sup.0 wire (d=1 mm) in 6 mL with 30 mM of NaBr added at 22 C. Initially the Cu.sup.II concentration is low, but in 45 min it reaches a much higher value, which is approximately the same time as the end of the 106 min induction period.
(149) The Effect of Initially Added Cu.sup.IIBr.sub.2 on the Polymerization:
(150) The effect of initially added Cu.sup.IIBr.sub.2 on polymerizations under the conditions: [OEOA].sub.0:[HEBiB].sub.0:[Cu.sup.IIBr.sub.2].sub.0:[Me.sub.6TREN].sub.0=100:1:x:0.2 (where x=0 or 0.01 for 0 or 100 ppm), [OEOA]=0.41 M, 10 cm of Cu.sup.0 wire (d=1 mm) in 6 mL with 30 mM of NaBr added at 22 C. and graphs of the evolution of monomer conversion with time and the evolution of M.sub.n and M.sub.w/M.sub.n with conversion displayed little difference although the final MWD of the reaction conducted in the presence of 100 ppm CuBr.sub.2 was lower 1.14.
(151) The Effect of the Concentration of Monomer on the Polymerization:
(152) Polymerization were conducted using either 18 wt % monomer, or 50 wt % monomer under the conditions [OEOA].sub.0:[HEBiB].sub.0:[Cu.sup.IIBr.sub.2].sub.0:[Me.sub.6TREN].sub.0=100:1:0.01:0.2 with 10 cm of Cu.sup.0 wire (d=1 mm) gave similar results. A longer induction period was observed for the 50 wt % case, 75 min vs. 45 min, and higher M.sub.w/M.sub.n values were also observed, 1.3 vs 1.16.
(153) Model Activation Experiments in 18 wt % OEOA in Water:
(154) As seen in
(155) Dependence of the Activation Rate Coefficient of OEOBrP by Cu.sup.0 with [Me.sub.6TREN].sub.0:
(156) Values for k.sub.a0.sup.app were obtained from activation experiments under the conditions: [OEOBrP].sub.0=20 mM, 18% OEOA in water, 10 cm Cu.sup.0 wire (d=1 mm) in 4.5 mL at 22 C. with different [Me.sub.6TREN].sub.0 and it was observed that the ligand concentration seems to only have a strong effect on the value of k.sub.a0.sup.app below a certain minimal concentration, which seems to be 2.5 mM for Me.sub.6TREN which is qualitatively consistent with literature reports in DMSO. [Percec, V. et. al.; J. Polym. Sci., Part A: Polym. Chem. 2009, 47, 5629; Matyjaszewski, K.; et. al.; Macromolecules 2013, 46, 3803; and Nicolas, J.; et al., Macromolecules 2012, 45, 7388]
(157) Determination of the Activation Rate Coefficient of OEOBrP and HEBiB by Cu.sup.I/Me.sub.6TREN in H.sub.2O and 18% wt OEOA in H.sub.2O:
(158) Cyclic voltammetry was used to determine the activation rate coefficients of the initiators OEOBrP and HEBiB. An example of a set of CVs showing the effect of scan rate on the catalytic current enhancement is shown in
(159) Table 1 lists the sequence of reactions occurring during cyclic voltammetry of [Cu.sup.IIL].sup.2+/RX as well as the kinetic and thermodynamic parameters required to carry out digital simulations. The standard reduction potential of [Cu.sup.IIL].sup.2+ was measured by cyclic voltammetry, whereas the Nicholson method [Anal. Chem. 1965, 37, 1351] was used to determine the standard electron transfer rate coefficient k.sub.s. The transfer coefficient was assumed to be 0.5. Since a new peak couple was not observed when Br.sup. was added to a solution of [Cu.sup.IIMe.sub.6TREN].sup.2+, it was assumed that the two complexes have identical redox properties, in other words the two complexes had the same halidophilicities. In the literature, the K.sub.ATRP for the reaction between HEBiB and Cu.sup.I/TPMA in water has been reported to be 0.15. [Angew. Chem. Int. Ed. 2011, 50, 11391] We used that value for the simulations of cyclic voltammetry data and determination of activation rate coefficients in all aqueous systems investigated and reported in this application.
(160) The association constant between Br.sup. and [Cu.sup.IIMe.sub.6TREN].sup.2+ is K.sub.Br.sup.II=4.4 M.sup.1 in pure water. [Inorg. Chim. Acta 1997, 255, 111.] Herein it was assumed that the association/dissociation equilibria are fast so that they constituted conditions of pre-equilibrium for the activation step. Therefore, a large value for k.sub.Br.sup.II=k.sub.Br.sup.I=10.sup.4 M.sup.1 s.sup.1 was used. Simulations have shown that the degree of catalysis becomes independent of k.sub.Br.sup.II and k.sub.Br.sup.I for sufficiently large values.
(161) The final important parameters required by the simulation program are the diffusion coefficients of the reagents [Cu.sup.IIMe.sub.6TREN].sup.2+, OEOBrP and HEBiB. They were determined by cyclic voltammetry of the compounds, according to the following equations valid for reversible (eq. 8) and irreversible (eq. 8) systems at 25 C.:
I.sub.p=(2.6910.sup.5)n.sup.3/2AD.sup.1/2C.sup.1/2(8)
I.sub.p=(2.9910.sup.5).sup.1/2nAD.sup.1/2C.sup.1/2(9)
(162) where n is the number of exchanged electrons, D is the diffusion coefficient, A is the area of the electrode and is the transfer coefficient. The values of D obtained using eq. 8 for the copper complex and eq. 9 for the initiators are reported in Table 2.
(163) TABLE-US-00001 TABLE 1 Parameters for the digital simulation of cyclic voltammetry of catalytic activation of RX by [Cu.sup.IMe.sub.6TREN].sup.+. Reaction .sup.a H.sub.2O H.sub.2O:OEOA = 82:18 [Cu.sup.IIL].sup.2+ + e.sup. [Cu.sup.IL].sup.+ E.sup. = 0.48 V E.sup. = 0.34 V k.sub.s = 10.sup.2 cm s.sup.1; = 0.5 k.sub.s = 1.5 10.sup.3 cm s.sup.1; = 0.5 [Cu.sup.IL].sup.+ + RX
[XCu.sup.IIL].sup.+ + R* K.sub.ATRP = 0.15 .sup.2 K.sub.ATRP 10.sup.4 b [XCu.sup.IIL].sup.+
[Cu.sup.IIL].sup.2+ + X.sup. K.sub.Br.sup.II = 4.4 M.sup.1; .sup.3 K.sub.Br.sup.II = 10.sup.2 M.sup.1 c k.sub.Br.sup.II = 10.sup.4 M.sup.1s.sup.1 k.sub.Br.sup.II = 10.sup.4 M.sup.1s.sup.1 [XCu.sup.IIL].sup.+ + e.sup.
[XCu.sup.IL] E.sup. = 0.48 V E.sup. = 0.34 V k.sub.s = 10.sup.2 cm s.sup.1; = 0.5 k.sub.s = 1.5 10.sup.3 cm s.sup.1; = 0.5 [XCu.sup.IL]
[Cu.sup.IL].sup.+ + X.sup. K.sub.Br.sup.I = 4.4 M.sup.1 K.sub.Br.sup.I = 10.sup.2 k.sub.Br.sup.I = 10.sup.4 M.sup.1s.sup.1 k.sub.Br.sup.I = 10.sup.4 M.sup.1s.sup.1 R* + R* .fwdarw. R R k.sub.t0 = 2.7 10.sup.8 M.sup.1s.sup.1 d k.sub.t0 = 2.7 10.sup.8 M.sup.1s.sup.1 d R* + TEMPO .fwdarw. R-TEMPO k.sub.tT = 10.sup.8 M.sup.1s.sup.1 4 .sup.a L = Me.sub.6TREN, X = Br, RX = OEOBrP or HEBiB; T = 25 C. .sup.b K.sub.ATRP in 18 wt % OEOA in water is expected to be lower than in water, but simulations with values as small as 10.sup.4 do not affect the simulation results, see FIG. 6. .sup.c Estimated value, taking into consideration medium effects. In pure water, K.sub.Br.sup.II = 4.4 M.sup.1, [Inorg. Chim. Acta 1997, 255, 111. ] therefore the value K.sub.Br.sup.II = 10.sup.2 M.sup.1 was chosen to account for the lower polarity of the reaction medium. .sup.d Estimated for tertiary radicals in 18% PEO-400 in H.sub.2O at room temperature. [Macromol. 2009, 42, 6348-6360. ]
(164) TABLE-US-00002 TABLE 2 Diffusion coefficients of [Cu.sup.IMe.sub.6TREN].sup.+, HEBiB and OEOBrP at 25 C. H.sub.2O H.sub.2O-OEOA 82:18 Substrate 10.sup.6 D (cm.sup.2 s.sup.1) 10.sup.6 D (cm.sup.2 s.sup.1) [Cu.sup.IMe.sub.6TREN].sup.+ 2.2 0.78 OEOBrP 3.1 0.28 HEBiB 6.0
(165) Voltammetric simulations were carried out for a large number of values and the results were plotted as I.sub.p,c/I.sub.p,d versus log . To simplify the comparison between experimental and simulated data, the latter were first fit to appropriate functions that perfectly interpolate all data. Two equations (eqs. 10 and 11) were used, depending on whether the theoretical curve presents a maximum or a plateau and examples of the fittings are reported in
(166)
where y.sub.0, a, b, c, d, e, f, x.sub.01 and x.sub.02 are fitting parameters.
(167) The procedure for the determination of k.sub.a1 was as follows. The experiment was carried out with fixed values of and a set of I.sub.p,c/I.sub.p,d versus log =log(RTC.sub.[Cu.sub.
(168) In the simulations of the catalytic system in 18 wt % OEOA in water K.sub.ATRP is not known but is expected to be much lower than value of 0.15 observed in pure water. To take this possibility into consideration a series of simulations with different K.sub.ATRP values were carried out and the results are reported in
(169) Evolution of UV-Vis-NIR Spectrum of Cu.sup.IIBr.sub.2/Me.sub.6TREN in Pure Water:
(170) As seen in
(171) Disproportionation Equilibrium Constants, Comproportionation and Disproportionation Rate Coefficients:
(172) As highlighted in the literature, [Macromol. 2013, 46, 3793] when comproportionation experiments are performed, the comproportionation rate coefficient, corrected for the S/V ratio, can be determined from the slope of Cu.sup.II evolution and the K.sub.disp.sup.L value using the following equation:
(173)
where t is the time, r is the ratio of ligand to initial Cu.sup.II, c is the integrand conversion up until that point which reached value cony. In this work, a discrete integration was performed and the integral is plotted against time. The slope of this integral is k.sub.comp.sup.app, and k.sub.disp.sup.app is determined from the K.sub.disp.sup.L value.
(174)
(175) Each comproportionation experiment was subject to this treatment, and the values of the comproportionation and disproportionation coefficients are given in Table 3.
(176) TABLE-US-00003 TABLE 3 Conditions and disproportionation/comproportionation rate coefficients and equilibrium constant for disproportionation of 2.5 mM of [Cu.sup.IIBr.sub.2].sub.0 with an excess Me.sub.6TREN in 18% OEOA at 22 C. Length Cu.sup.0/cm S/V Ratio k.sub.comp.sup.app k.sub.disp.sup.app Entry (wire d = 1 mm) (cm.sup.1) [Cu.sup.II].sub.0/[Me.sub.6TREN].sub.0 K.sub.disp.sup.L (cm s.sup.1) (cm s.sup.1) 1 20 1.40 8 22 2.3 10.sup.5 5.1 10.sup.4 2 5 0.35 8 22 2.5 10.sup.5 5.5 10.sup.4 3 10 0.70 8 27 2.7 10.sup.5 7.3 10.sup.4 4 10 0.70 4 18 2.5 10.sup.5 4.5 10.sup.4 5 10 0.70 2.1 23 .sup.2 10.sup.5 .sup.4 10.sup.4
(177) Kinetic Simulation of RDRP of OEOA.sub.480 in the Presence of Cu.sup.0:
(178) PREDICI (version 6.3.2) was used for all kinetic modeling. Table 4 below presents the kinetic model used and all rate coefficients.
(179) TABLE-US-00004 TABLE 4 Kinetic Model and Rate Coefficients for Modeling RDRP in the presence of Cu.sup.0 at 22 C. Reaction .sup.a Rate constant .sup.b
(180) All simulations were conducted as has been outlined in the literature. [Macromol. 2013, 46, 3816.] In the model, RX and R. represent the small molecule initiators and radicals, whereas P.sub.n-X and P.sub.n. represent polymeric dormant chains and radicals, respectively. Cu.sup.II X.sub.2/L represents entire population of Cu.sup.II species. The notation k.sup.app is used for apparent kinetic rate coefficients, which are the rate coefficients based on the total concentration of Cu species in a given oxidation state and do not take into consideration binding with halide and ligand. The only exceptions are the deactivation of radicals by Cu.sup.II species and activation of alkyl halides by Cu.sup.I species, which can only occur by reaction with the Cu.sup.IIX/L.sup.+ and Cu.sup.I/L.sup.+ complexes, respectively. These rapidly equilibrate with the Cu.sup.II/L.sup.++ and Cu.sup.IX/L complexes, respectively. When simulating the heterogeneous reactions, overall rate coefficients (k.sup.over) were calculated, taking into account the apparent rate constants (k.sup.app) and the Cu.sup.0 surface area and reaction volume (k.sup.over=k.sup.appS/V). For all simulations the only source of Cu.sup.0 is the wire surface area. All the rate coefficients take into account the exemplary polymerization media, 18 wt % OEOA in H.sub.2O. The comproportionation, disproportionation, Cu.sup.0, and Cu.sup.I activation by P.sub.n-X rate coefficients were evaluated in this work. Rate coefficient of activation of RX (R=HEBiB and OEOBrP respectively) by Cu.sup.0 was scaled based on experiments previously conducted in pure H.sub.2O,
(181) The value of rate coefficient of activation of RX by Cu.sup.0 was calculated in the following manner:
(182)
(183) Rate coefficients of deactivation by Cu.sup.I (k.sub.d0 and k.sub.d0i) were calculated based on principle of microscopic reversibility [Onsager, L. Phys. Rev. 1931, 37, 405] from the following equations:
(184)
(185) All the polymer populations, including the dormant species (P.sub.n-X), propagating species (P.sub.n.) and dead chains (T) were used for calculation of the number average degree of polymerization (DP.sub.n) and molecular weight distribution (MWD), M.sub.w/M.sub.n.
(186)
(187) Taking all this information into consideration an example was conducted with the following ratio of reagents: [OEOA]:[HEBiB]:[Me.sub.6TREN]:[CuBr.sub.2]=100:1:0.2:0.01 with 30 mM NaBr and the final analysis indicated an increase in soluble transition metal complexes from 100 to 600 ppm Cu which means 500 ppm Cu were generated indicating that 5% excess ligand was consumed in relation to added initiator (HEBiB), I.e. 25% of the added ligand was consumed during formation of additional soluble transition metal complexes.
(188) Furthermore the calculations indicate that the rate of copolymerization could be controlled by a controlled rate of addition of the ligand to the reaction.
(189) Extension of Range of Monomers to NIPAM:
(190) a range of polymerization parameters was examined, such as targeted degree of polymerization (DP) and surface area of copper. Results of block copolymerization are summarized in Table 5.
(191) TABLE-US-00005 TABLE 5 Summary of PNIPAM and PEO-b-PNIPAM synthesis by SARA ATRP and eATRP. time [NIPAM]/[I]/ S/V k.sub.p.sup.app conv M.sub.n, theo M.sub.n.sup.app entry (h) [Cu.sup.IIBr.sub.2/2Me.sub.6TREN] (cm.sup.1).sup.a (h.sup.1).sup.b (%).sup.b (10.sup.3).sup.c (10.sup.3).sup.b M.sub.w/M.sub.n.sup.d 1 2 10/1.sup.e/0.005 0.68 1.017 90 1.2 1.2 1.07 2 12 100/1.sup.e/0.05 0.68 0.303 81 9.3 9.8 1.15 3 21 200/1.sup.e/0.1 0.68 0.137 52 12.0 11.7 1.29 4 21 200/1.sup.f/0.1 0.16 0.077 43 11.8 11.1 1.28 5 21 200/1.sup.f/0.1 0.34 0.096 49 13.2 11.8 1.28 6 21 200/1.sup.f/0.1 1.20 0.229 70 17.9 19.5 1.24 7 21 200/1.sup.f/0.1 2.06 0.302 75 19.0 21.2 1.19 8 1 200/1.sup.f/0.1 3.885 95 23.6 24.5 1.18 SARA ATRP: entries 1-7; eATRP: entry 8. General reaction conditions: T = 0 C.; V.sub.tot = 8 mL (in H.sub.2O/DMF = 9/1 by v/v) (except entry 4-8, V.sub.tot = 33 mL); [I].sub.0 = 4.1 mM (except entry 1: [I].sub.0 = 82.0 mM and entry 2: [I].sub.0 = 8.2 mM); [NIPAM].sub.0 = 0.8M; Supporting electrolyte concentration (tetraethylammonium bromide, TEABr) = 0.1M. .sup.aRatio of surface area (S) of Cu.sup.0 to total volume of reaction mixture (V); .sup.bMonomer conversion, apparent M.sub.n and k.sub.p were determined by .sup.1H NMR; .sup.cM.sub.n, theo = ([M].sub.0/[I].sub.0) conversion M.sub.monomer + M.sub.initator; .sup.dMWD was determined by DMF GPC with PEO standards; .sup.eI = hydroxyethyl -bromoisobutyrate (HEBiB); .sup.fI = poly(ethylene oxide) macroinitiators, PEO MI.
(192) Reaction conditions for runs whose kinetics are provided in [NIPAM]/[HEBiB]=100/1 or
[NIPAM]/[HEBiB]=200/1, [Cu.sup.IIBr.sub.2].sub.0=0.41 mM (500 ppm), [Me.sub.6TREN].sub.0=0.82 mM, T=0 C., [TEABr].sub.0=0.1 M, Cu.sup.0 powder (S/V=0.68 cm.sup.1), V.sub.tot=8 mL.
(193) Well controlled polymers were synthesized using aqueous SARA ATRP in the presence of Cu.sup.0 (powder; S/V=0.68 cm.sup.1) with 500 ppm of Cu.sup.II/L, in the presence of an excess of bromide salt, [TEABr].sub.0=0.1 M. This concentration of Cu/L species generates essentially transparent, colorless solutions and represents a 5-100 fold reduction in Cu/L relative to previous reports of ca. 2,500-50,000 ppm Cu.sup.I/L used for pre-disproportionation in water.
(194) Effect of Targeted Degree of Polymerization:
(195) The effect of initial molar ratio of NIPAM monomer to initiator on the homopolymerization was investigated in the presence of Cu.sup.IIBr.sub.2/Me.sub.6TREN catalyst complex as reported in Table 5, entries 1-3,
(196)
and followed the first order with respect to P-X concentration. Values of k.sub.p.sup.app increased approximately linearly with [I].sub.0,
(197) Influence of the Surface Area of Cu to Solution Volume Ratio (S/V);
(198) Since Cu.sup.0 was added to the reaction in the form of a powder (Table 5, entries 4-5) or a sponge (Table 5, entries 6-7) it still predominantly acts as a supplemental, rather than major activator of alkyl halides, [Polym Chem-Uk 2014, 5 (15), 4396-4417] four separate experiments were conducted with varying amounts of Cu.sup.0 surface area to solution volume ratio, S/V=0.16, 0.34, 1.20, and 2.06 cm.sup.1, respectively (
(199)
Molecular weights increased linearly with conversion,
(200) Use of Silver as Activator Regenerator:
(201) The initial Ag as activator regenerator ATRP in water was polymerization of OEOA.sub.480 with HEBiB as an initiator. Reaction Conditions: [OEOA].sub.0:[HEBiB].sub.0:[Cu.sup.IIBr.sub.2].sub.0:[TPMA].sub.0=65:1.0:0.04:0.08 (615 ppm Cu.sup.II), 5.0 cm Ag.sup.0 wire (d=2 mm), in water, [OEOA].sub.0=1.14 M, 50 C. The reaction was well controlled with a linear increase in MW with conversion and narrow MWD (PDI1.10 at 60% conversion). Results are shown in
(202) Electrochemically Mediated ATRP of NIPAM.
(203) A series of experiments explored eATRP of NIPAM under standard polymerization conditions; Cu.sup.IIBr.sub.2/Me.sub.6TREN, DP=200, and T=0 C. E.sub.1/2 values for Cu.sup.IIBr.sub.2/Me.sub.6TREN complex were measured in the absence and presence of a PEO MI. The CV response of XCu.sup.II/L drastically changed when the initiator was added; the cathodic peak approximately doubled in height while the anodic one decreased, clearly indicating that Cu.sup.I/L rapidly reacted with PEO MI, 1. The weight fraction of PNIPAM was 0.84 (Table 1, entry 8) based on monomer consumption. According to this equation, the calculated MWD of PNIPAM block was 1.25, indicating that well-defined polymers were synthesized by eATRP under optimized conditions. In addition, clean shift towards higher molecular weights was observed on GPC demonstrating efficient chain extension of PEO-MI to a block copolymer.
(204) Photoinduced Polymerization of OEOMA.sub.500.
(205) A number of reactions with varied conditions were carried out for the photoinduced ATRP of OEOMA.sub.500 in water. Conditions used for the standard polymerization reaction of OEOMA at low concentration of Cu with excess salt were carried out under these typical conditions: OEOMA.sub.500 (1.15 ml, 2.5 mmol), PEOBPA (11 mg, 5.55 mol), CuBr.sub.2 (0.55 mol), TPMA (2.2 mol) and NaBr (0.055 mmol) were mixed in a 25 ml Schlenk flask and then dissolved in water (10.35 mL). For even lower concentrations of Cu, a stock solution was prepared in water by adding 1.23 mg of Cu in 10 ml of deionized water. The mixture was then homogenized and deoxygenated by bubbling with nitrogen for 45 mins. It was then placed inside a violet LED lamp (0.9 mW/cm.sup.2, 392 nm wavelength) and samples were taken throughout the course of the reaction for GPC and NMR measurements. The samples for NMR were prepared by dissolving the polymer in D.sub.2O. The GPC was prepared by dissolving the polymer in THF and adding a drop of toluene in it as standard. The sample was dried by passing it through a filter of anhydrous sodium carbonate and then copper was removed by passing through a filter of neutral alumina before measuring the GPC.
(206) TABLE-US-00006 TABLE 6 Results for photoinduced aqueous ATRP of OEOMA.sub.500 with different Cu concentrations..sup.a Cu concentration Time Conversion Entry Conditions (ppm) (h) (%).sup.b M.sub.n, th.sup.c M.sub.n, GPC.sup.d M.sub.w/M.sub.n.sup.d 1 x = 9 20000 4 60 137000 97000 1.07 2 x = 3 6600 6 54 123500 101000 1.20 3 x = 1 2200 6 69 157250 125000 1.26 4 x = 0.1 220 4 94 213000 142000 1.26 5 x = 0.1 with 5 mM NaBr 220 4 78 177000 114000 1.11 6 x = 0.1 with 5 mM NaCl 220 6 44 101000 16000 4.05 7 x = 0.05 110 3 70 160000 230000 1.56 8 x = 0.01 22 3 80 182000 322000 1.96 9 x = 0.01 with 5 mM NaBr 22 4 85 193000 213000 1.25 10 x = 0.01 with 30 mM NaBr 22 4 55 126000 103000 1.17 .sup.aReaction conditions: [OEOMA.sub.500].sub.0/[PEO.sub.2000BPA].sub.0/[CuBr.sub.2].sub.0/[TPMA].sub.0 = 450/1/x/4x in 90% (v/v) water with irradiation by 392 nm at 0.9 mW/cm.sup.2 at room temperature; .sup.bdetermined by .sup.1H NMR; .sup.ccalculated on the basis of conversion (i.e. M.sub.n, th = M.sub.PEOBPA + [OEOMA.sub.500].sub.0/[PEO.sub.2000BPA].sub.0 conversion M.sub.monomer); .sup.ddetermined by GPC in THF, based on linear PMMA as calibration standard.
(207) PhotoATRP was extended in aqueous media using low ppm of Cu/tris(2-pyridylmethyl)amine (TPMA) catalyst. This system features low catalyst concentrations as low as 22 ppm molar with respect to monomer under benign conditions (irradiation with visible light at room temperature in aqueous media), so they can be widely adapted to biological applications.
(208) Photoinduced ATRP in water was first attempted to polymerize oligo (ethylene oxide) methyl ether methacrylate (OEOMA, M.sub.n=500) using poly(ethylene oxide)-bromophenylacetate (PEO.sub.2000-BPA) as macroinitiators under visible light irradiation (392 nm at 0.9 mW/cm.sup.2). TPMA was used as ligands since they give stable Cu.sup.I complexes without any significant disproportionation in water.
(209) The effect of Cu concentration was originally investigated, and results are summarized in Table 6. The polymerization at high concentration of Cu (20,000 ppm) gave a linear semilogarithmic kinetic plot versus conversion. Excellent control over the reaction was obtained. The experimental molecular weights were in good agreement with the theoretical values with dispersities as low as 1.07 (entry 1, Table 6). Photoinduced ATRP with 6600 ppm, 2200 and 220 ppm of Cu (x=3, 1 and 0.1) still provided well-defined polymers (M.sub.w/M.sub.n=1.20-1.26, entries 2-4, Table 6). The reaction with further lower loading of Cu catalyst (110 and 22 ppm) gave polymers with much higher M.sub.n compared to theoretical M.sub.n as well as broad distribution (M.sub.w/M.sub.n=1.56 and 1.96, entries 7 and 8, Table 1, respectively). It is worth pointing out that the molecular weight was decreased with increasing conversion at only 22 ppm Cu catalyst used, indicating a non-controlled free radical polymerization. This could attribute to the low deactivator concentration resulting from dissociation of halogen atom from the CuBr.sub.2/TPMA complex, which is one of the major challenges associated with aqueous ATRP especially with low Cu concentration. The addition of excess of halide salt shifts the equilibrium towards deactivator complex BrCu.sup.II Br/TPMA, promoting efficient deactivation, Scheme 5.
(210) Therefore, photoinduced aqueous ATRP were investigated at low Cu concentration along with the addition of halide salts. The results are summarized in Table 1 and
(211) A similar reaction using 220 ppm Cu catalyst with 5 mM NaCl gave polymer with a bimodal distribution (M.sub.n=16000, M.sub.w/M.sub.n=4.05, entry 6, Table 1), indicating a poor control in presence of chloride ions.
(212) Table 7 and
(213) TABLE-US-00007 TABLE 7 Results for photoinduced ATRP of OEOMA with various DP.sub.T in aqueous media..sup.a Time Conversion Entry DP.sub.T (h) (%).sup.b M.sub.n, th.sup.c M.sub.n, GPC.sup.d M.sub.w/M.sub.n.sup.d 1 450 4 72 164000 147000 1.21 2 250 4 70 90000 79200 1.21 3 200 4 59 61000 56300 1.16 4 100 4 39 21500 17500 1.16 5 450.sup.c 4 61 84000 84800.sup.f 1.18.sup.f 6 200.sup.c 4 47 30000 31900.sup.f 1.10.sup.f 7 100.sup.c 4 40 14000 17100.sup.f 1.10.sup.f .sup.aReaction conditions: [OEOMA.sub.500].sub.0/[PEO.sub.2000BPA].sub.0/[CuBr.sub.2[.sub.0/[TPMA].sub.0 = DP.sub.T/1/0.1/0.4 in 90% water with 5 mM NaBr at room temperature with irradiation by 392 nm 0.9 mW/cm.sup.2; .sup.bdetermined by .sup.1H NMR; .sup.ccalculated on the basis of conversion (i.e. M.sub.n, th = M.sub.PEOBPA + DP conversion M.sub.monomer); .sup.ddetermined by GPC in THF, based on linear PMMA as calibration standard; .sup.eOEOMA.sub.300 as monomer; .sup.fdetermined by GPC in water, based on linear PEG as calibration standard.
(214) Chain Extension of Polymer of OEOMA.sub.500 with OEOMA.sub.300:
(215) To confirm the utility of this photoinduced ATRP in aqueous media, chain extension of the homopolymer of OEOMA.sub.500 was conducted with OEOMA.sub.300. OEOMA.sub.500 was polymerized under standard conditions to form the macroinitiator. OEOMA.sub.500 (1.15 ml, 2.5 mmol), PEOBPA (11 mg, 5.55 mmol), CuBr.sub.2 (0.55 mmol), TPMA (2.2 mmol) and NaBr (0.055 mmol) were mixed in a 25 ml Schlenk flask and dissolved in water (10.35 mL). The mixture was deoxygenated by bubbling with nitrogen for 45 mins. It was then placed inside the LED lamp and was allowed to polymerize for 6 hours with conversion around 90% providing the POEOMA500 macroinitiator, M.sub.n=115,000 and M.sub.w/M.sub.n=1.13, OEOMA.sub.300 was deoxygenated in a separate flask by bubbling with nitrogen for 40 mins and (1 ml, 2.5 mmol) was then added to the same mixture for chain extension. The mixture was then irradiated for one more hour and the polymerization reached 12% conversion giving P(OEOMA.sub.500)-b-P(OEOMA.sub.300) M.sub.n=139,000 and M.sub.w/M.sub.n=1.2. These experiments show that a well-controlled photoATRP can be conducted when the initial concentration of a catalyst complex is as low as 22 ppm.
(216) The procedures disclosed herein allow one to conclude that in contrast to prior art procedures employing pre-reaction disproportionation of a high concentration of Cu.sup.I/L catalyst complex, in excess of 10,000 ppm, prior to the addition of monomer (SET LRP) a very well-controlled polymerization can be conducted in the presence of a low concentration of Cu.sup.II/L complex, preferentially lower than 500 ppm, starting with a solution of comonomers in polar media that in the initial exemplary procedure is activated by the addition of solid Cu.sup.0, exemplified herein by copper wire, that participates in a comproportionation reaction to form a very low concentration of Cu.sup.I, approximately 1% of the added Cu.sup.II, for a reaction conducted in an initial solution of 18% monomers in aqueous media, that is the actual activator of the polymerization.
(217) As disclosed herein by developing a full understanding of the kinetics of the reactions associated with Cu.sup.I complexes in a polymerization conducted in polar media it is now possible to conduct the reaction with low ppm levels of added copper complexes in the presence of an added chemical or a physical activator regenerator.
(218) It will be understood that the present description illustrates those aspects of the invention relevant to a clear understanding of the invention. Certain aspects that would be apparent to those of ordinary skill in the art and that, therefore, would not facilitate a better understanding of the invention have not been presented in order to simplify the present description. Although only a limited number of embodiments of the present invention are necessarily described herein, one of ordinary skill in the art will, upon considering the foregoing description, recognize that many modifications and variations of the invention may be employed. All such variations and modifications of the invention are intended to be covered by the foregoing description and the following claims.