BRANCHED POLYMERS

Abstract

Responsive or degradable branched polymers may be prepared by the free radical polymerisation of a multivinyl monomer in the presence of a chain transfer agent, using a source of radicals, wherein the extent of propagation is controlled relative to the extent of chain transfer to prevent gelation of the polymer. The multivinyl monomer may comprise a cleavable group, for example an ester, or a multiplicity of such groups, between two vinyl groups. Said monomer may be a macromonomer containing multiple cleavage sites.

Claims

1-31. (canceled)

32. A method of preparing a responsive or degradable branched polymer comprising: free radical polymerisation of one or more multivinyl monomers in the presence of one or more chain transfer agents and a source of radicals, wherein the extent of propagation is controlled relative to the extent of chain transfer to prevent gelation of the polymer.

33. The method of claim 32 wherein the multivinyl monomer is a divinyl monomer.

34. A method of preparing a responsive or degradable branched polymer comprising: free radical polymerisation of one or more multivinyl monomers in the presence of one or more chain transfer agents and a source of radicals, wherein propagation is controlled relative to chain transfer to achieve a polymer having a multiplicity of vinyl polymer chain segments wherein the average vinyl polymer chain contains between 1 and 3 multivinyl monomer residues.

35. The method of claim 32 wherein the multivinyl monomer comprises a cleavable group between two vinyl groups.

36. The method of claim 35 wherein said cleavable group is an ester.

37. The method of claim 32 wherein the multivinyl monomer comprises multiple cleavable sites between the polymerizable vinyl groups.

38. The method of claim 37 wherein the number of said cleavable sites is 5 or more.

39. The method of claim 37 wherein the cleavable sites are ester linkages.

40. The method of claim 32 wherein said multivinyl monomer is, or is derived from, itaconic acid.

41. The method of claim 40 wherein said multivinyl monomer comprises the following structure: ##STR00011##

42. The method of claim 32 wherein during free radical polymerisation the conversion of double bond functionality to saturated carbon-carbon bonds in the polymer is 80% or more.

43. The method of claim 32 wherein at least 1 equivalent of chain transfer agent is used relative to multivinyl monomer.

44. The method of claim 32 further comprising the incorporation of one or more monovinyl monomers.

45. The method of claim 32 wherein the multivinyl monomer is a multimethacrylate, multiacrylate or multiacrylamide.

46. The method of claim 32 wherein the chain transfer agent is a thiol.

47. The method of claim 32 wherein a monomer is incorporated which has epoxide functionality.

48. The method of claim 32 wherein a monomer is incorporated which has tertiary amine functionality.

49. A branched polymer obtained by the method of claim 32.

50. A responsive or degradable branched polymer product comprising one or more multivinyl monomer residues and chain transfer residues, comprising on average between 0.9 and 3.3 chain transfer residues per multivinyl monomer residue.

51. The responsive or degradable branched polymer product of claim 50 wherein the multivinyl monomer residues are divinyl monomer residues, comprising on average between 0.9 and 1.1 chain transfer residues per divinyl monomer residue.

52. The responsive or degradable branched polymer product of claim 50, wherein the multivinyl monomer residues comprise less than 20 mol % unreacted double bond functionality.

53. The responsive or degradable branched polymer product of claim 50, further comprising monovinyl monomer residues.

54. The responsive or degradable branched polymer of claim 50, wherein the branched polymer product comprises a multiplicity of vinyl polymer chain segments having an average length of between 1 and 3 multivinyl monomer residues.

55. The product of claim 50 wherein branches between vinyl polymer chains comprise a cleavable group.

56. The product of claim 55 wherein said cleavable group is an ester.

57. The product of claim 50 wherein the branches between vinyl polymer chains comprise multiple cleavable sites per branch.

58. The product of claim 57 wherein the number of said cleavable sites is 5 or more.

59. The product of claim 57 wherein the cleavable sites are ester linkages.

60. The product of claim 50 wherein the multivinyl monomer residue is, or is derived from, itaconic acid.

61. The product of claim 60 wherein the multivinyl monomer residue comprises the following structure: ##STR00012##

62. The product of claim 50 wherein the multivinyl monomer residue is a residue of a multimethacrylate, multiacrylate or multiacrylamide.

63. The product of claim 50 wherein the chain transfer agent residue is a thiol residue.

64. The product of claim 50 comprising a monomer residue which has epoxide functionality.

65. The product of claim 50 comprising a monomer residue which has tertiary amine functionality.

Description

DESCRIPTION OF THE DRAWINGS

[0197] The present invention will now be described in further non-limiting detail and with reference to the drawings in which:

[0198] FIGS. 1 and 2 show free radical mechanisms involved in one embodiment of the present invention;

[0199] FIGS. 3 and 4 show schematic representations of a branched polymer;

[0200] FIG. 5 shows NMR spectra at different stages during the polymerization process;

[0201] FIG. 6 shows examples of some compounds which may be used as divinyl monomers, some of which are responsive or degradable;

[0202] FIG. 7 shows examples of some compounds which may be used as chain transfer agents;

[0203] FIG. 8 shows a further schematic representation of a branched polymer, highlighting the vinyl polymer chain lengths within the product;

[0204] FIG. 9 shows a mass spectrum of components of a responsive or degradable polymer in accordance with an embodiment of the present invention;

[0205] FIG. 10 shows a mass spectrum of polymer species comparative to those of FIG. 9;

[0206] FIGS. 11 to 15 show NMR spectra of some branched polymer products prepared using trivinyl monomers amongst other reagents; and

[0207] FIG. 16 shows a generic representation of components of a divinyl monomer and a fragment of a polymer of the present invention;

[0208] FIG. 17 shows a decrease in the relative amounts of higher molecular weight species present after degradation of a responsive product in basic water;

[0209] FIGS. 18 and 19 show examples of divinyl monomers which are macromonomers and contain multiple ester cleavage sites;

[0210] FIG. 20 shows a representation of a fragment of a degradable branched polymer which may be prepared by the polymerization of a degradable macromonomer;

[0211] FIG. 21 shows an NMR spectrum of a mixture of degradable macromonomers;

[0212] FIG. 22 shows an NMR spectrum of a degradable branched polymer;

[0213] FIG. 23 shows GPC traces of degradable branched polymers and a degradable macromonomer precursor; and

[0214] FIG. 24 shows a photograph of a cured product of a copolymer prepared from a degradable divinyl monomer and an epoxy-containing monovinyl monomer.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

[0215] Whereas the present invention relates to the preparation of branched polymers which are responsive or degradable, some of the examples herein relate to the formation of branched polymers which are not responsive or degradable. These have been included because they show structures and use components which can be used in combination with the responsive or degradable components of the present invention.

[0216] With reference to FIG. 1, radical activity is transferred to a chain transfer agent such as dodecanethiol, by reaction with a radical derived from an initiator such as AIBN, or by reaction with a radical derived from a divinyl monomer (e.g. from EGDMA) which has previously reacted with a source of radicals. This results in a chain transfer agent radical [CH.sub.3(CH.sub.2).sub.11S. in FIG. 1] which (FIG. 2) reacts with divinyl monomer in the present invention and results in propagation of the chain.

[0217] A schematic representation of the resultant branched polymer is shown in FIGS. 3 and 4. Where DDT is used as the chain transfer agent the circle represents a moiety which comprises a dodecyl chain. Although the polymer is built up by vinyl polymerisation, nevertheless the chemistry of the longest chains in the product is determined by the other functional groups present in the divinyl monomer, and accordingly in some cases the longest chains may be polyesters.

[0218] One advantage of the present invention is that the vinyl functionality of the monomers can react completely. Experimental proof of this has been obtained by NMR analysis: in FIG. 5, the top NMR spectrum, in respect of a sample at the start of the reaction, shoes .sup.1H NMR due to the presence of double bond hydrogens. After reaction, the NMR trace (bottom) shows no detectable double bond signals.

[0219] FIG. 8 shows a branched polymer made from the divinyl monomer EGDMA and chain transfer agent DDT (shown as spheres). Thick lines indicate the C—C bonds which were double bonds in the monomer. The numerals indicate the vinyl polymer chain lengths. It can be seen that there are 13 chains of length 1, five chains of length 2, six chains of length 3, one chain of length 4 and one chain of length 5.

[0220] The product shown in FIG. 8 is consistent with the discussion above which refers to some standard systems having (n+1) chain transfer agent residues per n divinyl monomer residues, and average vinyl polymer chain lengths of 2n/(n+1). The ratio of chain transfer residues to divinyl monomer residues is 26:25 i.e. (n+1):n, such that the number of chain transfer residues per divinyl monomer residue is 26/25=1.04. The average polymer chain length is [(1×13)+(2×5)+(3×6)+(4×1)+(5×1)]/(13+5+6+1+1)=50/26=1.923 i.e. 2n/(n+1). All vinyl groups have reacted, i.e. the conversion is 100%. Each vinyl residue is directly vinyl polymerised to on average 48/50=0.96 other divinyl monomer residues.

Example 1—EGDMA as Divinyl Monomer and DDT as Chain Transfer Agent

[0221] Thus, in one embodiment, the divinyl monomer is EGDMA, the chain transfer agent is DDT, and a small amount of AIBN is used to provide a source of radicals. The reaction may be carried out in toluene, or other solvents.

[0222] Different ratios of chain transfer agent to divinyl monomer were investigated. A summary of the results is shown in the following table.

[0223] EGDMA—Monomer

[0224] DDT—CTA

[0225] AIBN—Thermal initiator

[0226] Toluene—Solvent (wt. 50%)

[0227] Standard Conditions: [0228] Oil bath at 70° C. [0229] Reaction time—24 hrs [0230] Mass of AIBN was based on 1.5% mol of double bonds in monomer

TABLE-US-00009 Number of EGDMA: “repeat DDT units” per EGDMA DDT Gel in final object (mol (mol for- polymer Vinyl Mw Mn based on eq.) eq.) mation product.sup.a conversion.sup.a (kg/mol).sup.b (kg/mol).sup.b Ð a.sup.d Mw 1 0.5 Yes — — — — — — — 1 1 Yes — — — — — — — 1 2 No 1:1 >99% 26.6 8.8 3.02 0.28  66 1 2 No 1:1 >99% 19.4 5.35 3.6 0.234  48 1 1.33 No 1:0.95 >99% 144.0 12.7 11.4 0.3 360 .sup. 1.sup.c 1.33.sup.c No.sup.c 1:1.05.sup.c  >99%.sup.c 157.4 4.4 35.6 0.287 393 .sup. 1.sup.e 1.33.sup.e No.sup.e 1:1.sup.e  >99%.sup.e 228.55.sup.e 2.83.sup.e 80.84.sup.e 0.339.sup.e .sup. 570.sup.e 1 1.25 No 1:1 >99% 216.86 10.19 21.27 0.299 541 1 1.11 No 1:1.05 >99% 3,484.0 52.96 65.79 0.368 8,700  .sup.adetermined by .sup.1H NMR (400 MHz) in CDCl.sub.3. .sup.bdetermined by triple detection GPC .sup.cscale-up reaction (3 time the previous scale) .sup.dMark-Houwink parameter: [η] = KM.sup.a .sup.eReaction carried out in ethyl acetate at 50 wt % solid content

[0231] From these results it can be seen that, for these reagents, gelation can be avoided by the use of more equivalents of the chain transfer agent DDT than the brancher EGDMA, and that the final product contains about the same amount of chain transfer agent as brancher. It can also be seen that changing the amount of chain transfer agent can affect the degree of polymerisation. For example, if just enough chain transfer agent is used to avoid gelation, a high molecular weight product can be obtained. The skilled person is able to tailor the product accordingly.

[0232] Experimental (for approximately a 5 g scale reaction):

[0233] In a typical experiment, 55.9 mg of AIBN (0.3406 mmol, 1.5% vs. double bonds) were placed in a single neck 25 mL round bottomed flask. EGDMA (2.14 mL, 11.352 mmol, 0.75 eq), DDT (3.62 mL, 15.13 mmol, 1 eq) and Toluene (6.14 mL, 50 wt % vs. EGDMA and DDT) were added to the reactor and the mixture was purged by argon sparge for 15 minutes under stirring. The reactor was then placed in a preheated oil-bath at 70° C. for up to 24 hours. The resulting crude material was analysed by .sup.1H NMR and showed no evidence of remaining double bonds after 2.5 hours. Further purification of the product was performed by evaporating the toluene on a rotary evaporator, dissolving the resulting mixture in THF and precipitating in methanol at room temperature (THF:methanol=1:10 v/v). The resulting white precipitate was isolated and dried under vacuum at 40° C. (yield ˜85%).

Example 2—EGDMA as Divinyl Monomer and Benzyl Mercaptan as Chain Transfer Agent

[0234]

TABLE-US-00010 EGDMA: benzyl Benzyl mercaptan in EGDMA Mercaptan Gel final polymer Vinyl Mw Mn (mol %) (mol %) formation product.sup.a Conversion.sup.a (kg/mol).sup.b (kg/mol).sup.b Ð a.sup.d 1 1 Yes — — — — — — 1 0.5 Yes — — — — — — .sup. 1.sup.c 2.sup.c    No.sup.c 1:1.1.sup.c  100%.sup.c 16.9.sup.c 3.1.sup.c 5.5.sup.c 0.288.sup.c 1 1.33 Yes — — — — — — 1 2 No 1:1.02 100% — — — — Details as Example 1, except: .sup.cReacted for 72 hours Purification by precipitation was carried out using THF and ethanol at 0° C. to produce a white precipitate.

Example 3—EGDMA as Divinyl Monomer and 2-Naphthalenethiol as Chain Transfer Agent

[0235]

TABLE-US-00011 EGDMA: 2- 2- naphthalenethiol EGDMA Naphthalenethiol Gel Reaction Time Vinyl in final polymer (mol %) (mol %) formation (hrs) conversion product 2 1 Yes 1 — — 1 1 No 24 Unable to Unable to determine.sup.a determine.sup.a 1 1 No 48 Unable to Unable to determine.sup.a determine.sup.a Details as Example 1 except: .sup.aUnable to analyse as it seems to be immiscible in chosen solvents: CDCl.sub.3, toluene and CDCl.sub.3, DMF and THF.

Example 4—EGDMA as Divinyl Monomer and a Dendron Thiol as Chain Transfer Agent

[0236] ##STR00007##

TABLE-US-00012 G1- EGDMA: DBOP DBOP in final EGDMA Thiol Gel polymer Vinyl Mw Mn (mol %) (mol %) formation product.sup.a conversion.sup.a (kg/mol).sup.b (kg/mol).sup.b Ð α.sup.d 1 2.5 No 1:1 86% 6.7 3.1 2.15 0.168 Details as Example 1.

Example 5—PEGDMA (Approximately 875 g Mol.SUP.−1.) as Monomer

[0237]

TABLE-US-00013 No. of repeat PEG- PEGDMA: units per dimeth- DDT in final object acrylate DDT Gel polymer Vinyl Mw Mn based (mol %) (mol %) formation product.sup.a conversion.sup.a (kg/mol).sup.b (kg/mol).sup.b Ð a.sup.c Mw 1 2 Yes — — — — — — — 1 1.33 Yes — — — — — — — 1 4 No 1:1.2 >99% 22.6 6.4 3.55 — 21 1 4 No 1:1.1 >99% — — — — — 1 3.33 No 1:1.1 >99% — — — — — 1 2.89 No 1:1.1 >99% 54.7 4.7 11.6 — 51 1 2.5 No 1:1.1 >99% 2,200 61 36.5 — 2037 M.sub.R.U. ≈ 1080 g/mol Details as Example 1 except: .sup.cMark-Houwink parameter: [η] = KM.sup.a

Example 6—PEGDMA (Approximately 3350 g Mol.SUP.−1.) as Divinyl Monomer and DDT as Chain Transfer Agent

[0238]

TABLE-US-00014 PEGDMA: PEG- DDT in No. of repeat dimeth- final units per acrylate DDT Gel polymer Vinyl Mw Mn object based (mol %) (mol %) formation product.sup.a conversion.sup.a (kg/mol).sup.b (kg/mol).sup.b Ð a.sup.c on Mw 1 1 Yes — — — — — — 1 4 No 1:1.3 100% 93.6 8.8 10.6 — 26 1 2.5 No 1:1.3 >99% 103.8 7.7 13.4 — 29 1 2 No 1:1.1 100% 106.7 9.5 11.2 — 30 Details as Example 5 except: M.sub.R.U. ≈ 3350 g/mol

Examples 7 and 8—Polymerisations of EGDMA with DDT, or PEGDMA (Mw 875) with DDT, at a Higher Temperature

[0239]

TABLE-US-00015 EGDMA: DDT in final EGDMA DDT Gel polymer Vinyl Mw Mn (mol %) (mol %) formation product.sup.a conversion.sup.a (kg/mol).sup.b (kg/mol).sup.b Ð a.sup.d 1 1 Yes — — — — — — 1 1.33 No 1:1 >99% — — — —

TABLE-US-00016 PEG- PEGDMA: dimethacrylate DDT Gel DDT in final Vinyl Mw Mn (mol %) (mol %) formation polymer product.sup.a conversion.sup.a (kg/mol).sup.b (kg/mol).sup.b Ð a.sup.d 1 2 Yes — — — — — — 1 2.5 No 1:1.1 >99% 1,600 28.9 55.3 — Details as Examples 1 and 5 except: Oil bath at 85° C. rather than 70° C.

Example 9: Divinyl Benzene as Divinyl Monomer and DDT as Chain Transfer Agent

[0240] Experimental.

[0241] In a typical experiment, 75.7 mg of AIBN (0.4608 mmol, 1.5% vs. double bonds) were placed in a single neck 25 mL round bottomed flask. DVB (2.19 mL, 15.36 mmol, 1 eq), DDT (3.68 mL, 15.36 mmol, 1 eq) and Toluene (5.91 mL, 50 wt % vs. DVB and DDT) were added to the reactor and the mixture was purged by argon sparge for 15 minutes under stirring. The reactor was then placed in a preheated oil-bath at 70° C. for up to 24 hours. Further purification of the product was performed by evaporating the toluene on a rotary evaporator, dissolving the resulting mixture in THF and precipitating in methanol at room temperature (THF:methanol=1:10 v:v).

TABLE-US-00017 DVB: CTA in final DVB DDT Solid Gel polymer Vinyl Mw Mn (eq.) (eq.) content Formation product.sup.a conversion.sup.a (kg/mol).sup.b (kg/mol).sup.b Ð.sup.b α.sup.c 1 1 50 wt % No 0.92:1.0 99% 69.8 1.5 45.2 0.263 1 2 50 wt % No 0.57:1.0 >99%  1.02 0.8 1.24 0.643 1 1 70 wt % Yes — — — — — — 1 1 60 wt % Yes — — — — — — 1 1 55 wt % No 0.86:1 99% 113.4 2 56.7 0.26 .sup.adetermined by .sup.1H NMR (400 MHz) in CDCl.sub.3. .sup.bdetermined by triple detection GPC .sup.cMark-Houwink parameter: [η] = KM.sup.a

Example 10: Divinylbenzene as Divinyl Monomer and Benzyl Mercaptan as Chain Transfer Agent

[0242] Experimental.

[0243] In a typical experiment, 18.9 mg of AIBN (0.1152 mmol, 1.5% vs. double bonds) were placed in a single neck 25 mL round bottomed flask. DVB (1.094 mL, 7.68 mmol, 0.5 eq), benzyl mercaptan (1.803 mL, 15.36 mmol, 1 eq) and Toluene (3.364 mL, 50 wt % vs. DVB and benzyl mercaptan) were added to the reactor and the mixture was purged by argon sparge for 15 minutes under stirring. The reactor was then placed in a preheated oil-bath at 70° C. for up to 24 hours. Further purification of the product was performed by evaporating the toluene on a rotary evaporator, dissolving the resulting mixture in THF and precipitating in methanol at room temperature (THF:methanol=1:10 v:v).

TABLE-US-00018 Benzyl DVB: DVB mercaptan Gel CTA in final Vinyl Mw Mn (eq.) (eq.) Formation polymer product.sup.a conversion.sup.a (kg/mol).sup.b (kg/mol).sup.b Ð.sup.b α.sup.c 1 1 Yes — — — — — — 1 2 No — 99% 0.6 0.5 1.2 1.2 1 1.33 No — 99% 3.63 0.78 4.652 0.194 1 1.25 No — 99% 6.175 0.71 8.72 0.171 1 1.11 No — 99% 28.7 0.91 31.65 0.209 .sup.adetermined by .sup.1H NMR (400 MHz) in CDCl.sub.3. .sup.bdetermined by triple detection GPC .sup.cMark-Houwink parameter: [η] = KM.sup.a

Example 11: Bisacrylamide as Divinyl Monomer and Thioglycerol as Chain Transfer Agent

[0244] Experimental

[0245] In a typical experiment, 16.0 mg of AIBN (0.0973 mmol, 1.5% vs. double bonds) were placed in a single neck 10 mL round bottomed flask. Bisacrylamide (0.5 g, 3.243 mmol, 0.5 eq), thioglycerol (TG; 0.56 mL, 6.5 mmol, 1 eq) and ethanol (1.49 mL, 50 wt % vs. bisacrylamide and TG) were added to the reactor and the mixture was purged by argon sparge for 15 minutes under stirring. The reactor was then placed in a preheated oil-bath at 70° C. for up to 24 hours. The product was obtained by removing the ethanol on a rotary evaporator.

TABLE-US-00019 Bisacrylamide: 1- CTA in final Vinyl Bisacrylamide Thioglycerol Gel polymer conver- Mw Mn (eq.) (eq.) Formation product.sup.a sion.sup.a (kg/mol).sup.b (kg/mol).sup.b Ð.sup.b α.sup.c 1 2 No — — 1.6 1.3 1.23 — .sup.adetermined by .sup.1H NMR (400 MHz) in CDCl.sub.3. .sup.bdetermined by triple detection GPC .sup.cMark-Houwink parameter: [η] = KM.sup.a

Example 12: PEGDMA (875 g/Mol) as Divinyl Monomer and Thioglycerol as Chain Transfer Agent

[0246] Experimental.

[0247] In a typical experiment, 19.3 mg of 4, 4′-azobis(4-cyanovaleric acid) (ACVA; 0.0687 mmol, 1.5% vs. double bonds) were placed in a single neck 10 mL round bottomed flask. PEGDMA (2 g, 2.29 mmol, 1 eq), 1-thioglycerol (TG; 0.824 g, 7.62 mmol, 3.33 eq) and anhydrous ethanol (3.58 mL, 50 wt % vs. PEGDMA and TG) were added to the reactor and the mixture was purged by argon sparge for 15 minutes under stirring. The reactor was then placed in a preheated oil-bath at 70° C. for up to 24 hours. Further purification of the product was performed by concentrating on a rotary evaporator and precipitating in hexane at room temperature.

TABLE-US-00020 PEGDMA: TG in final PEGDMA TG Gel polymer Vinyl Mw Mn (eq.) (eq.) Formation product.sup.a conversion.sup.a (kg/mol).sup.b (kg/mol).sup.b Ð.sup.b α.sup.c 1 5 No 1:2.5 >99% 10.2 0.1 98.4 / 1 3.33 No 1:1.75 >99% 415.3 6.05 68.65 / 1 2.5 Yes — — — — — — All reaction performed in ethanol at 50 wt % .sup.adetermined by .sup.1H NMR (400 MHz) in CDCl.sub.3. .sup.bdetermined by triple detection GPC .sup.cMark-Houwink parameter: [η] = KM.sup.a

Example 13: PEGDMA (875 g/Mol) as Divinyl Monomer with Mixed Chain Transfer Agents (DDT and Thiolglycerol)

[0248] Experimental.

[0249] In a typical experiment, 11.3 mg of AIBN (0.0686 mmol, 1.5% vs. double bonds) were placed in a single neck 25 mL round bottomed flask. PEGDMA (2 g, 2.76 mmol, 1 eq), DDT (0.578 g, 2.86 mmol, 1.25 eq), 1-thioglycerol (TG; 0.309 g, 2.86 mmol, 1.25 eq) and toluene (8.34 mL, 50 wt % vs. PEGDMA, TG and DDT) were added to the reactor and the mixture was purged by argon sparge for 15 minutes under stirring. The reactor was then placed in a preheated oil-bath at 70° C. for up to 24 hours. Further purification of the product was performed by evaporating the toluene on a rotary evaporator, dissolving the resulting mixture in chloroform and precipitating in petroleum ether at 0° C. (CHCl.sub.3:petroleum ether=1:10 v:v).

TABLE-US-00021 % of 1- % of DDT Thioglycerol Gel in final in final Vinyl Brancher DDT TG For- polymer final polymer conver- Mw Mn (eq.) (eq.) (eq.) mation product.sup.a product.sup.a sion.sup.a (kg/mol).sup.b (kg/mol).sup.b Ð.sup.b α.sup.c 1 1.25 1.25 No 26 74 >99% 76.12 3.2 23.6 / 1 1.25 1.25 No 24 76 >99% 9.3 0.51 18.19 / 1 1.875 0.625 No 51 49 >99% 28.25 2.45 11.55 / 1 1.5 1 No 32 68 >99% 131 3.82 34.4 / 1 1.25 1.25 No 30 70 >99% 1,040 11.8 88.3 0.462 1 1.5 1 No 37 63 >99% 395 2.73 144 0.392 1 1.875 0.625 No 55 45 >99% 348 7.46 46.6 0.381 1 1.75 0.75 No 50 50 >99% 964 19.3 50 0.473 .sup.adetermined by .sup.1H NMR (400 MHz) in CDCl.sub.3. .sup.bdetermined by triple detection GPC .sup.cMark-Houwink parameter: [η] = KM.sup.a

Example 14: Incorporation of a Monovinyl Monomer (Benzyl Methacrylate) into the System (EGDMA as Divinyl Monomer and DDT as Chain Transfer Agent)

[0250] Experimental

[0251] In a typical experiment, 49.7 mg of AIBN (0.303 mmol, 1.5% vs. EGDMA double bonds) were placed in a single neck 25 mL round bottomed flask. EGDMA (1.903 mL, 10.09 mmol, 0.75 eq), Benzyl methacrylate (BzMA; 0.456 mL, 2.691 mmol, 0.2 eq), DDT (3.222 mL, 13.453 mmol, 1 eq) and toluene (6 mL, 50 wt % vs. EGDMA, BzMA and DDT) were added to the reactor and the mixture was purged by argon sparge for 15 minutes under stirring. The reactor was then placed in a preheated oil-bath at 70° C. for up to 24 hours. Further purification of the product was performed by evaporating the toluene on a rotary evaporator, dissolving the resulting mixture in THF and precipitating in methanol at room temperature (THF:methanol=1:10 v:v).

TABLE-US-00022 Brancher: MonoVM: CTA in EGDMA BzMA DDT Gel purified Vinyl Mw Mn (eq.) (eq.) (eq.) Formation product.sup.a conversion.sup.a (kg/mol).sup.b (kg/mol).sup.b  .sup.b α.sup.c 1 0.267 1.33 No 1:0.2:1 >99% 94.1 10.6 8.9 0.275 .sup.adetermined by .sup.1H NMR (400 MHz) in CDCl.sub.3. .sup.bdetermined by triple detection GPC .sup.cMark-Houwink parameter: [η] = KM.sup.a

Example 15: BDME as Stimuli-Responsive (Acid-Cleavable) Divinyl Monomer and DDT as Chain Transfer Agent

[0252] Experimental.

[0253] In a typical experiment, 26.7 mg of AIBN (0.163 mmol, 1.5% vs. double bonds) were placed in a single neck 10 mL round bottomed flask. BDME (1.71 g, 5.44 mmol, 1 eq), DDT (1.47 g, 7.29 mmol, 1.33 eq) and toluene (3.69 mL, 50 wt % vs. BDME and DDT) were added to the reactor and the mixture was purged by argon sparge for 15 minutes under stirring. The reactor was then placed in a preheated oil-bath at 70° C. for up to 24 hours. Further purification of the product was performed by evaporating the toluene on a rotary evaporator, dissolving the resulting mixture in THF and precipitating in ethanol at 0° C. (THF:ethanol=1:10 v:v).

TABLE-US-00023 BDME:DDT in final BDME DDT Gel polymer Vinyl Mw Mn (eq.) (eq.) Formation product.sup.a conversion.sup.a (kg/mol).sup.b (kg/mol).sup.b  .sup.b α.sup.c 1 1.33 No 0.99:1 >99% 20.5 7.4 2.76 0.341 .sup.adetermined by .sup.1H NMR (400 MHz) in CDCl.sub.3. .sup.bdetermined by triple detection GPC .sup.cMark-Houwink parameter: [i] = KM.sup.a

Example 16—Experiments, Using Degradable Monomers, to Help Elucidate the Polymerisation Mechanisms and Structures within the Products

[0254] To establish the mechanistic basis of the polymerisation/telomerisation, two reactions were conducted under near-identical conditions. The first utilised an acid sensitive divinyl monomer—BDME—as in Example 15 above and shown in FIG. 9. The resulting polymer was then treated with acid to cleave all of the diacetal units within what could conventionally be termed a step-growth polymer backbone and yield a distribution of vinyl oligomers that are representative of the free radical telomerisation during the synthesis. The acid degradation was achieved as follows:

[0255] THF (9 mL) was added to 1 mL of the crude product (before purification) of the reaction described above. Then, trifluoroacetic acid (TFA; 10 μL, ˜2 eq vs BDME) was added to the solution and stirred for 72 hours at room temperature. Basic alumina (˜2 g) was added to the reaction mixture followed by filtration with a 200 nm syringe filter. The solvent was evaporated on a rotary evaporator and the resulting product was analysed by GPC and MALDI-TOF mass spectroscopy.

[0256] The GPC analysis showed very low molecular weight species that were difficult to study using the available analytical instrument. In order to generate accurate analytical data, the sample was subjected to MALDI-TOF mass spectrometry, yielding the mass spectrum shown in FIG. 9.

[0257] The species present are polymethacrylic acid oligomers and telomers with a single CTA at one end of the chain and are generated during the cleavage as follows:

##STR00008##

[0258] The MALDI-TOF spectrum (negative ion) clearly indicates that a distribution of telomers and oligomers are present with a chain length of up to 18 units. These correspond to polyacid monomer residues within the branched polyacetal structure. MALDI-TOF and other mass spectrometry techniques are well known to not fully represent the concentration of the different species present within the analysis sample and the purification of the sample will have disproportionately removed different species within the mixture. For example, the units relating to reaction of the CTA radical with a single vinyl group (n=1) are not readily observable. Additional signals are present due to oxidation of thio-ethers resulting from the presence of the CTA within the distribution of species. This is as expected by those skilled in the art.

[0259] The type of structures present in such systems would be impossible to replicate using step growth polymerisation methods. In this case, polycondensation of polyacid mixtures and ethylene glycol would likely lead to gelation at low conversions due to the components being so highly functional (e.g. 18-acid functional)

[0260] To compare with conventional free radical polymerisation conditions, a model reaction using a mono-vinyl monomer (methyl methacrylate—MMA) was conducted as follows, strongly replicating the BDME conditions but in the absence of divinyl monomer.

[0261] Methyl methacrylate (2.27 g, 22.7 mmol, 1 eq) was purged with nitrogen for 15 minutes. 1-Dodecanethiol (3.06 g, 15.13 mmol, 1.33 eq), AIBN (0.0559 g, 0.341 mmol) and toluene (6.16 mL) were added to the 25 mL round-bottomed flask and purged with nitrogen for 5 minutes. The reaction flask was heated in an oil bath at 70° C. and stirred for 24 hours and then cooled. The reaction mixture was concentrated by rotary evaporation and the resulting product was analysed by GPC and MALDI-TOF mass spectroscopy.

[0262] The MALDI-TOF mass spectrum (positive ion—sodium adducts comprise the main distribution) of this product is seen in FIG. 10.

[0263] As can be readily seen, the telomerisation/oligomerisation of MMA under identical conditions generates a near identical distribution of identifiable species. Structures up to 18 monomer units are seen through the free radical polymerisation of MMA under these conditions and such species were seen in the homopolymerisation of the divinyl monomer BDME.

Example 17—Reactions Using Trivinyl Monomer TMPTMA

[0264] Experimental (for approximately a 5 g scale reaction):

[0265] In a typical experiment, 43.7 mg of AIBN (0.266 mmol, 1.5% vs. double bonds) were placed in a single neck 25 mL round bottomed flask. Trimethylolpropane trimethacrylate (TMPTMA) (1.887 mL, 5.91 mmol, 0.4 eq), DDT (3.539 mL, 14.78 mmol, 1 eq) and Toluene (5.769 mL, 50 wt % vs. TMPTMA and DDT) were added to the reactor and the mixture was purged by nitrogen sparge for 15 minutes under stirring. The reactor was then placed in a preheated oil-bath at 70° C. for up to 24 hours. The resulting crude material was analysed by .sup.1H NMR and showed no evidence of remaining double bonds after 24 hours. Further purification of the product was performed by evaporating the toluene on a rotary evaporator, dissolving the resulting mixture in THF and precipitating in methanol (MeOH) at room temperature. The product was collected by removing the supernatant and was rinsed with fresh MeOH. Finally, the resulting polymer was dried under vacuum at 40° C. for 12 hours. After purification, the polymer was collected with a yield of 73 (m.sub.polymer/m.sub.DDT+TMPTMA). The purified product was further analysed by GPC and .sup.1H NMR.

[0266] Trivinyl monomer was homopolymerized, and was also copolymerised with divinyl monomer and with monovinyl monomer. It was possible to incorporate various functionalities e.g. tertiary amine functionality and epoxy functionality, thereby facilitating further reaction possibilities.

[0267] DEAEMA: 2-(diethylamino)ethyl methacrylate

[0268] GlyMA: Glycidyl methacrylate

[0269] The ratios in the first column indicate the relative molar amounts of reagents used in the reaction.

[0270] Proton NMR spectra of some of the products are shown in FIGS. 11 to 15:

[0271] FIG. 11—homopolymerisation of trivinyl monomer;

[0272] FIG. 12—polymerisation of trivinyl monomer with epoxy-functional monovinyl monomer;

[0273] FIG. 13—polymerisation of trivinyl monomer with tertiary amine-functional monovinyl monomer;

[0274] FIG. 14—comparison of spectra of FIGS. 11 and 12;

[0275] FIG. 15—comparison of spectra of FIGS. 11 and 13.

TABLE-US-00024 NMR Mn MH cony. Mw (kg/mol) (kg/mol) α Trivinyl monomer [DDT]:[TMPTMA]   4:1 >99% 9.76 1.86 5.24 0.179   3:1 >99% 20.04 1.53 13.07 0.261 2.5:1 >99% 239.90 4.04 59.34 0.313   2:1 >99% 1,080 15.22 70.97 0.332 Trivinyl + divinyl monomer [DDT]:[TMPTMA]:[EGDMA] 5:1:0.5 >99% 11.08 0.97 11.48 0.254 5:1:1 >99% 25.15 1.21 20.79 0.177 5:1:1.5 >99% 93.14 3.34 27.89 0.297 5:1:2 >99% 279.22 6.49 43.00 0.318 Trivinyl + monovinyl monomer [DDT]:[TMPTMA]:[BzMA] 2.2:1:0.1 >99% 428.83 7.12 60.24 0.308 2.2:1:0.45 >99% 417.23 8.34 50.04 0.332 Trivinyl + monovinyl monomer [DDT]:[TMPTMA]:[BzMA] 2:1:0.6 >99% 1,347 20.92 64.41 0.324 2:1:1 >99% 726.14 18.61 39.01 0.311 Trivinyl + monovinyl monomer (tertiary amine functionality) [DDT]:[TMPTMA]:[DEAEMA] 2:1:0.15 >99% 682.43 17.35 39.32 0.305 2:1:0.6 >99% 560.65 62.91 8.91 0.322 2:1:0.8 >99% 228.63 31.37 7.29 0.319 Trivinyl + monovinyl monomer (epoxy functionality) [DDT]:[TMPTMANGlyMA] 2:1:0.2 >99% 3,168 1,518 2.088 0.538 2:1:0.8 >99% 978.4 416.3 2.35 0.43 2:1:1 >99% 810.9 291.9 2.778 0.428

Example 18

[0276] The polymer products can have various properties depending on the functional groups within the monomers and other components. For example, degradable, biodegradable, compostable or responsive properties can be incorporated.

[0277] By way of example, FIG. 16 shows schematically a divinyl monomer and a fragment of a polymer made from it. In this divinyl monomer, A and L could be any substituent, E and J could be any linker (e.g. an ester), and G could be additional linking chemistry (of course there could just be one linking moiety). M denotes CTA, T initiator fragment and Q and X terminating groups from chain transfer. Degradable components could be introduced via for example E, J or G, or alternatively or additionally M or Q.

[0278] Accordingly, the products of the present invention may be biodegradable.

Example 19—Dilution Experiments

[0279] In contrast to the experimental procedures for some of the Examples described above which refer to a solids weight % of 50%, a series of experiments was carried out with a solids weight % of 10%, using EGDMA as DVM and DDT as CTA. Attempts were made to carry out the reaction using lower amounts of CTA per equivalents DVM. It was found that gels formed if 0.4 equivalents or fewer of CTA were used per 1 equivalent DVM. The gel point was found to be between 0.4 and 0.5. Non-gelled products were formed in the following cases:

TABLE-US-00025 .sup.1H NMR (CDCl.sub.3) Vinyl EGDMA: GPC (THF) DDT Gel % Conversion DDT in final Mw Mn Entry (equiv.) Formation Yield (%) product (kg/mol) (kg/mol) α dn/dc 1 0.45 No 75 >99 0.95:1 6119 418.1 14.6 0.374 0.1099 2 0.5 No 82 >99 1.65:1 1223 40.22 30.4 0.261 0.108 3 0.75 No 59 >99 1.52:1 51.3 3.62 14.2 0.229 0.1182 4 1 No 53 >99  1.3:1 14.02 2.34 5.99 0.206 0.1051 5 1.33 No 59 >99   1:1 5.74 0.686 8.374 0.193 0.1103 DVM: EGDMA Solvent: ethyl acetate Solid wt % = 10% AIBN %: 1.5% DDT equivalents are per 1 equivalent EGDMA Entries 1 and 2 were purified by precipitation into Me0H at 0 degrees C. Entries 3 to 5 were purified by precipitation into Me0H at room temperature

[0280] Of note is that non-gelled products were formed when as little as 0.45 equivalents of CTA were used per equivalent of DVM (reaction time: 24 hours).

[0281] The appearances and textures observed in the products were as follows:

[0282] Entry 1: white crunchy powder

[0283] Entry 2: white fine powder

[0284] Entry 3: white solid

[0285] Entry 4: clear, sticky, hard “liquid”

[0286] Entry 5: clear, sticky, soft “liquid”

[0287] Further experiments were carried out at solid weight % of 10, 25 and 50:

TABLE-US-00026 .sup.1H NMR (CDCl.sub.3) EGDMA: GPC (THF) Reactn Vinyl DDT in Mw Mn EGDMA DDT Solid Time Yield Conv. final (kg/ (kg/ Entry (equiv.) (equiv.) wt. % (hrs) (%) (%) product mol) mol) α dn/dc 1 1 1.33 10 24 59 >99 1:1 5.74 0.686 8.374 0.193 0.1103 2 1 1.33 25 24 73 >99 0.91:1 14.75 0.658 22.43 0.215 0.0976 3 1 1.33 50 24 67 >99 1:1 229 2.83 80.8 0.339 0.0883 Entry 1: clear, sticky, soft “liquid” Entry 2: turbid, soft liquid Entry 3: clear, sticky, hard “liquid”

Example 20—Kinetics of Polymerisation with Varying Amounts of AIBN

[0288] The polymerisations proceeded more slowly but still effectively even at low concentrations of initiator:

TABLE-US-00027 .sup.1H NMR (CDCl.sub.3) Actual Theo- Theo- Ratio of EGDMA: GPC (THF) retical retical Gel Reaction EGDMA: Vinyl DDT in Mw Mn EGDMA DDT Form- Time % DDT @ Conv final (kg/ (kg/ Entry (equiv.) (equiv.) ation (hrs) AIBN t = 0 (%) product mol) mol) α dn/dc 1 1 1.33 No 24 1.5 — >99   1:1 229 2.83 80.84 0.339 0.0883 2 1 1.33 No 24 0.15 1:1.36 99 0.92:1 182.71 1.84 99.3 0.329 0.0966 3 1 1.33 No 24 0.05 1:1.33 94 0.97:1 81 1.72 46.96 0.319 0.0979 4 1 1.33 No 48 0.05 1:1.33 99 TBC TBC TBC TBC TBC TBC

TABLE-US-00028 .sup.1H NMR (CDCl.sub.3) EGDMA + DDT EGDMA + DDT EGDMA + DDT EGDMA + DDT System at 1.5% System at 0.05% System at 0.15% System at 0.05% AIBN AIBN AIBN AIBN (2) Reaction Vinyl Conversion Vinyl Conversion Vinyl Conversion Vinyl Conversion Sample Time (hr) (%) (%) (%) (%) 1 0 0 0  0  0 2 0.5 48 8 — — 3 1 83 20 — — 4 1.5 98 33 — — 5 2 >99 45 — — 6 2.5 >99 53 — — 7 3 >99 59 23 16 8 3.5 >99 68 — — 9 4 >99 74 — — 10 5 >99 82 — — 11 6 >99 86 45 39 12 24 >99 99 94 95 13 48 N/A N/A N/A 99

Example 21—Co-Polymerisation of EGDMA and Dibutyl Itaconate (“BioLIFT”) with DDT

[0289] In this example, dibutyl itaconate (a monovinyl monomer derived from itaconic acid) is incorporated.

[0290] In a typical experiment, ethylene glycol dimethacrylate (1 g, 5.05 mmol, 1 equiv.), dibutyl itaconate (0.244 g, 1.01 mmol, 0.2 equiv.), 1-Dodecanethiol (1.36 g, 6.73 mmol, 1.33 equiv.), AIBN (0.0249 g, 0.151 mmol) and ethyl acetate (2.89 mL) were added to a 10 mL round-bottomed flask and purged with nitrogen for 15 minutes. The reaction flask was heated at 70° C. and stirred for 24 hours and then cooled. The reaction mixture was concentrated by rotary evaporation, followed by dilution with THF and purified via precipitation into methanol at room temperature which afforded a white precipitate (1.98 g, 76%). A sample of the product was taken for .sup.1H NMR spectroscopic analysis in CDCl.sub.3 and for GPC analysis in THF.

TABLE-US-00029 .sup.1H NMR (CDCl.sub.3) Reaction Vinyl EGDMA: GPC (THF) EGDMA BioLIFT DDT Time Conversion BioLIFT: DDT Mw Mn Entry (equiv.) (equiv.) (equiv.) Solvent (hrs) (%) in final product (kg/mol) (kg/mol) α dn/dc 1 (128) 1 0.2 1.33 Ethyl 24 >99.9 1.0:1.0:0.2 99 6.1 16 0.298 0.1037 Acetate 2 (130) 1 0.1 1.33 Ethyl 24 >99.9 1.0:1.0:0.1 94 2.2 44 0.305 0.0927 Acetate

Example 22—Acid Functional Brancher (BDIB) Synthesis

[0291] In this example, a degradable brancher (divinyl monomer) based on itaconic acid was prepared.

[0292] Itaconic anhydride (25 g, 223 mmol, 2 equiv.), 1, 4-Butanediol (10.1 g, 112 mmol, 1 equiv.), 4-Methoxyphenol (0.025 g, 0.201 mmol) and acetone (44.3 mL) were added to a 50 mL round-bottomed flask and fitted with a condenser. The reaction flask was heated at 70° C. and stirred for 8 hours. The reaction mixture was concentrated by rotary evaporation which afforded a white precipitate (23.44 g, 67%). A sample of the product was taken for .sup.1H NMR spectroscopic analysis in d.sub.6-DMSO.

Example 23—Co-Polymerisation of EGDMA and BDIB with DDT

[0293] In a typical experiment, ethylene glycol dimethacrylate (1 g, 5.05 mmol, 0.5 equiv.), BDIB (1.59 g, 5.05 mmol, 0.5 equiv.), 1-Dodecanethiol (2.72 g, 13.5 mmol, 1.33 equiv.), AIBN (0.0497 g, 0.303 mmol) and ethyl acetate (5.88 mL) were added to a 25 mL round-bottomed flask and purged with nitrogen for 15 minutes. The reaction flask was heated at 70° C. and stirred for 24 hours and then cooled. The reaction mixture was concentrated by rotary evaporation and purified via trituration into petroleum ether at room temperature which afforded a white precipitate (3.72 g, 70%). A sample of the product was taken for .sup.1H NMR spectroscopic analysis in CDCl.sub.3 and for GPC analysis in THF.

TABLE-US-00030 .sup.1H NMR (CDCl.sub.3) DVM Gel Reaction Vinyl EGDMA: BDIB: GPC (THF) EGDMA BDIB DDT Forma- Time Conversion DDT in final Mw Mn Entry (equiv.) (equiv.) (equiv.) tion (hrs) (%) product (kg/mol) (kg/mol) α dn/dc 1 (189).sup.a 0.4 0.6 0.5 No 24 65 TBC 16.3 3.43 4.74 0.137 0.0473 2 (186) 0.4 0.6 1.33 No 24 >99.9 TBC 15.9 5.01 3.13 0.175 0.0982 3 (181) 0.5 0.5 1.33 No 24 >99.9 TBC 23.2 6.72 3.45 0.188 0.1 4 (172) 0.63 0.37 1.33 No 24 90.8 TBC 53.9 9.65 5.58 0.652 0.1002 5 (173) 0.8 0.2 1.33 No 24 >99.9 TBC 95.3 6.55 14.6 0.443 0.1029 6 (174).sup.b 0.87 0.13 1.33 No 24 >99.9 TBC 89.5 4.36 20.5 0.267 0.0941 7 (101) 1 0 1.33 No 24 >99.9 1.0:1.0 229 2.83 80.8 0.339 0.0883 .sup.aConducted at 10 wt. % solid content. Soluble (& foaming) at pH 7 .sup.bEntry 6 is 0.72:1 (DVM; CTA)

[0294] Degradation in Water Tests were carried out on three samples to observe properties before and after 5 days in basic water.

[0295] Before (upper part of FIG. 17):

TABLE-US-00031 GPC (THF) DVM Mw Mn EGDMA BDIB DDT (kg/ (kg/ Entry (equiv.) (equiv.) (equiv.) mol) mol) α dn/dc 1 0.63 0.37 1.33 53.9 9.65 5.58 0.652 0.1002 (172) 2 0.8 0.2 1.33 95.3 6.55 14.6 0.443 0.1029 (173) 3 0.87 0.13 1.33 89.5 4.36 20.5 0.267 0.0941 (174)

TABLE-US-00032 After (lower part of Figure 17): DVM GPC (THF) EGDMA BDIB DDT Mw Mn Entry (equiv.) (equiv.) (equiv.) (kg/mol) (kg/mol) α dn/dc 1 0.63 0.37 1.33 43.9 19.5 2.35 0.216 0.1046 2 0.8 0.2 1.33 17.5 10.2 1.72 0.247 0.1032 3 0.87 0.13 1.33 14.1 3.31 4.51 0.273 0.1028

[0296] As shown in FIG. 17, a decrease in the intensity of higher molecular weight species is observed, indicating that degradation has occurred.

[0297] Mixed DVM and CTA System:

TABLE-US-00033 CTA .sup.1H NMR (d.sub.6-DMSO) DVM Reaction Vinyl EGDMA: BDIB: TG: GPC (THF) EGDMA BDIB 1-TG DDT Time Conversion DDT in final Mw Mn Entry (equiv.) (equiv.) (equiv.) (equiv.) (hrs) (%) product (kg/mol) (kg/mol) α dn/dc 1 0.30 0.45 0.5 0.5 24 99.7 TBC 8.41 2.56 3.29 0.15 0.0359 (188) (40%) (60%) Soluble (and foaming) at pH 5-7

Example 24—Use of Poly(Caprolactone) Dimethacrylate (PCLDMA): A Divinyl Macromonomer which is a Degradable Brancher Due to the Presence of Multiple Cleavable Ester Linkages Between the Vinyl Groups

[0298] Syntheses of PCLDMA

[0299] The macro-monomer PCLDMA was synthesised in two steps: firstly, the acid catalysed ring opening polymerisation (ROP) of caprolactone (CL) using a bifunctional initiator (benzene dimethanol—this specific molecule was selected due to its aromatic nature in order to have extensive characterisation of the resulting polymer via .sup.1H NMR); secondly, esterification of the hydroxyl chain ends with methacryloyl chloride to yield the di-vinyl polycaprolactone (PCL) brancher, PCLDMA.

##STR00009## [0300] the PCLDMA macro-promonomer

##STR00010## [0301] the PCLDMA macro-monomer, in which n represents the number of CL units in each part of the monomer

[0302] FIGS. 18 and 19 show idealistic representations of two PCLDMA macromonomers: FIG. 18 shows PCLDMA 2k with 7 CL units either side of the bifunctional initiator; and FIG. 19 shows PCLDMA 6k with 30 CL units either side of the bifunctional initiator.

[0303] PCLDiOH, α, ω-Dthydroxy Funcllonalised Polycaprolactone

[0304] In a typical experiment targeting a DP.sub.n of 60, 1,4-benzenedimethanol (1.21 g, 8.8 mmol) and CL (60.0 g, 0.53 mol) were sealed in a dry RBF equipped with a magnetic stirrer bar. Toluene (anhydrous) (150 mL) was then injected to the sealed RBF followed by the addition of the acid catalyst MSA (0.6 mL, 9.2 mmol). The mixture was left to stir for 1.5 h at 55° C. The reaction was terminated by the addition of alumina (Brockmann, activated, basic) (5 g). The mixture was then filtered by gravity and the basic alumina collected in the filter paper washed with toluene (three washes, each 25 mL). The filtrate was rotary evaporated (70 mbar, 40° C.) to 50 mL. The mixture was then precipitated in petroleum ether (40-60° C.) (500 mL). The supernatant was poured away and the precipitate was dried in a vacuum oven at 40° C. overnight, yielding a white solid. The white solid was collected and analysed by .sup.1H NMR and TD-SEC.

[0305] PCLDMA Macro-Monomer

[0306] In a typical experiment targeting a DP.sub.n of 60, PCLDiOH, DP.sub.n 60 (20.0 g; 3.0 mmol; synthesis described above) was added to a dry RBF equipped with a magnetic stirrer bar and the RBF was sealed. TEA (anhydrous) (2 mL) and THF (anhydrous) (100 mL) were added. The mixture was stirred until a clear solution formed. An excess of methacroyl chloride (0.8 mL, 8.2 mmol) was added gradually over a 20 min period with an ice bath. A white precipitate formed upon addition of methacroyl chloride. The mixture was stirred for 24 h. The mixture was then filtered under gravity, with the filter paper being washed with THF (three washes, each 20 mL). The filtrate was then passed through a column filled with alumina (Brockmann, activated, basic) (5 g). 4-Methoxyphenol was added to the solution (20 mg, 16 μmop. The solution was then rotary evaporated (250 mbar, room temperature) to 50 mL. 4-Methoxyphenol (40 mg, 32 μmop was added to cold petroleum ether (40-60° C.) (500 mL). PCLDMA was then precipitated from THF into cold petroleum ether (40-60° C.), producing a white precipitate. The supernatant was then poured away and the precipitate was dried in a vac-oven, yielding a white solid. The white solid was characterised by .sup.1H NMR and TD-SEC.

[0307] PCLDMA Characterisation Data

[0308] FIG. 21 shows an .sup.1H NMR spectrum (CDCl.sub.3; 400 MHz) of PCLDMA DP.sub.n 14 (PCLDMA 2K). The singlets at 3.75 and 6.75 ppm, indicated by asterisks (*) are from the antioxidant 4-methoxy phenol. The precipitated product is a macromonomer mixture which contains mainly compounds in which both sides of the aromatic initiator have been polymerised with caprolactone (top structure in FIG. 21), and, to a lesser extent, compounds in which only one side of the aromatic initiator has been polymerised with caprolactone (bottom structure in FIG. 1). The smaller peaks for proton types a, b, c and h are from the monomer in which only one side of the aromatic initiator has been polymerised with caprolactone. The fact that mixtures of macromonomers of this kind may be obtained is not problematic because both types of compound are suitable for vinyl polymerisation.

[0309] Results of the GPC analysis for the different DP.sub.ns of the PCLDMA macro-monomers are shown in the table below which includes the M.sub.n and DP.sub.n observed by .sup.1H NMR, M.sub.n, M.sub.w, Ð and M-H α observed by GPC.

[0310] a: Determined by .sup.1H NMR of pure samples, b: Determined by GPC.

TABLE-US-00034 M.sub.n .sup.a M.sub.n .sup.b M.sub.w .sup.b Macro-monomer DP.sub.n .sup.a (kg/mol) (kg/mol) (kg/mol)   .sup.b M-H .Math. α .sup.b PCLDMA 2k 14 1.6 1.8 2.3 1.3 0.82 PCLDMA 6k 60 6.2 4.4 6.6 1.5 0.68

Example 25—Polymerisations of PCLDMA Macromonomers

[0311] FIG. 20 shows an example of a fragment of a degradable hyperbranched (HB) polymer formed by the free radical vinyl polymerisation of a PCLDMA macromonomer, using a thiol chain transfer agent (CTA), HSR.

[0312] Poly(PCLDMA) Synthesis

[0313] In a typical CTA mediated free radical polymerisation of PCLDMA DP.sub.n 60, AIBN (12 mg, 7.3 μmop, PCLDMA DP.sub.n 60 (3.0066 g, 0.48 mmol), TG (0.1026 g, 0.95 mmol) and toluene (4.9 g) were added to a dry RBF equipped with a magnetic stirrer bar. The solution was degassed via nitrogen sparge for 15 min. The solution was then heated at 70° C. for 24 h with constant stirring. An aliquot was taken in order to determine the vinyl conversion via .sup.1H NMR analysis, then, the solution was cooled to room temperature and precipitated into cold petroleum ether (100 mL). The supernatant was then poured away and the precipitate collected and dried in a vacuum oven at 50° C. overnight. The polymer was characterised by TD-SEC and .sup.1H NMR.

[0314] Poly(PCLDMA) Characterisation Data (NMR and GPC)

[0315] The following table shows data for poly(PCLDMA 6k) branched polymers synthesised using the macro-monomer PCLDMA 6k and chain transfer agents (CTA) dodecanethiol (DDT) and thiolglycerol (TG).

TABLE-US-00035 Targeted Observed [CTA]: [CTA]: Conver- [PCLDMA 6 k] [PCLDMA] sion Mn .sup.d Mw .sup.d Entry CTA ratio .sup.a ratio .sup.c (%) .sup.b (kg/mol) (kg/mol)   .sup.d M-H .Math. α .sup.d 1 DDT 1.5:1 1.2:1 ≥99 5.0 49.9 9.9 0.46 2 DDT 1.7:1 1.3:1 95 6.4 31.4 4.9 0.50 3 TG 1.9:1 1.5:1 95 7.1 34.9 4.9 0.50 .sup.a: Determined by .sup.1H NMR of crude samples at t = 0. .sup.b: Determined by .sup.1H NMR of crude samples at t = t.sub.f = end of the reactions. .sup.c: Determine by .sup.1H NMR of purified samples. .sup.d: Determined by TD-SEC.

[0316] FIG. 22 shows a .sup.1H NMR spectrum (CDCl.sub.3; 400 MHz) of poly(PCLDMA 6k) with thiolglycerol (TG) as the CTA (entry 3 in the table above).

[0317] FIG. 23 shows GPC traces of the poly(PCLDMA 6k) and the PCLDMA 6k macro-monomer.

Example 26—Degradation Studies Carried Out on Degradable Branched Polymers [Poly(PCLDMA)] and Also on Precursors Thereof

[0318] The degradation study used a control of commercially available PCL (M.sub.n=80 kg mol.sup.−1) in lipase solution to ensure the enzyme solution was active.

[0319] In preliminary experiments, degradation studies were performed on the macro-monomers prior to the CTA mediated free radical (FR) polymerisation step. The results of the degradation studies for the macro-monomers (entries 2 and 3 in the table below) showed that there was a significant amount of degradation in each case, with PCLDMA 2k and PCLDMA 6k showing almost complete degradation after 10 days. The percentage mass loss of the macro-monomers was comparable to the linear PCL (80 kg mol.sup.−1) control sample (entry 1 in the table below) which showed complete degradation after 10 days. The results from the degradation study provided proof of concept that the macro-monomers synthesised were degradable.

[0320] Samples of the different poly(PCLDMA) materials were placed in pre-weighed vials containing a solution of lipase (pseudomonas cepacian) in a buffered phosphate saline solution (pH 7.2) with sodium azide (0.02 wt %) at 37° C. with constant agitation for 10 days. The clear homogeneous aqueous phase was then carefully removed from the vials ensuring all solids were kept inside. The vials and solids were then washed with deionised water and the aqueous phase removal procedure was repeated. The vials and their content were then placed in a vacuum oven at 50° C. for 24 hours and the mass loss was assessed by weight difference.

[0321] The following table shows results of the degradation study of the macro-monomers and polymers of PCLDMA 2k and PCLDMA 6k, and the PCL (80 kg mol.sup.−1) control sample. The table contains the CTA, M.sub.w, initial mass of the film, the mass lost through degradation and the percentage mass lost with the error based on the equipment which was ±1 mg.

[0322] a: Determined by GPC

TABLE-US-00036 Percent- age M.sub.w .sup.a Initial Mass Mass Loss (kg Mass Loss (% ± Entry Sample mol.sup.−1) CTA (mg) (mg) % error) 1 Control 80.0 — 30.3 30.5 101 ± 1  2 PCLDMA 2k 2.3 — 31.9 30.8 97 ± 3 3 PCLDMA 6k 6.6 — 57.7 55.4 96 ± 2 4 Poly(PCLCMA 2k) 37.8 DDT 27.2 15.1 56 ± 3 5 Poly(PCLCMA 2k) 12.6 DDT 23.6 16.8 71 ± 4 6 Poly(PCLCMA 6k) 49.9 DDT 64.0 22.9 36 ± 1 7 Poly(PCLCMA 6k) 31.4 DDT 35.0 15.7 45 ± 2 8 Poly(PCLCMA 6k) 34.9 TG 66.1 32.6 49 ± 1

[0323] The results of the degradation study of poly(PCLDMA) (entries 4-8) show that the hyperbranched (HB) polymers synthesised from PCLDMA 2k and PCLDMA 6k were degradable by lipase. However, the mass lost after the 10 days in our standard conditions for the poly(PCLDMA)s were significantly less than that of the macro-monomers or the linear PCL (80 kg mol.sup.−1) control sample, which had a mass loss of 30.8±1 mg for PCLDMA 2k, 55.4±1 mg for PCLDMA 6k and 30.5±1 mg for the control sample. This lower mass loss is perhaps due to lipase being more active at points where the chain mobility is greater and in a HB polymer the chains are densely packed, reducing the mobility of the polymer chains and hence the accessibility of the enzyme to the ester bonds.

[0324] Comparing the results of poly(PCLDMA 2k) (entries 4 and 5), there is a slight increase in the mass lost going from entry 4 to entry 5. This increase in mass loss may be due to the molecular weight of the polymer decreasing from entry 4 to entry 5. This may because, as the molecular weight of the HB polymer increases, the amount of branching may increase. It is believed that the accessibility of the lipase to the ester bonds would be reduced by this branching, hence yielding lower levels of degradation when compared to lower molecular weight HB polymers.

[0325] Comparing the results of poly(PCLDMA 6k) (entries 6-8), there is a significant decrease in the mass lost going from entry 6 to entry 7. This result differs from the results of the polymers synthesised from PCLDMA 2k. As the mass lost over 10 days decreases with the molecular weight of the poly(PCLDMA 6k). Without wishing to be bound by theory, for the lower molecular weight poly(PCLDMA 6k), the chains may organise themselves when the film is made, providing some crystalline sections. In contrast the higher molecular weight poly(PCLDMA 6k) may be more amorphous due to the higher amount of branching preventing the organisation of the PCL chains. These amorphous PCL chains may be more accessible for the lipase and hence may result in an increase in the observed degradation of the HB polymer. Comparing entries 7 and 8, there is a significant increase in the mass loss of poly(PCLDMA 6k) which have similar molecular weight. This could be explained by the hydrophilicity of TG. The hydrophilic TG in entry 8 may lead to the chain ends of the polymer extending out into the aqueous phase and hence making the chain ends more accessible to the lipase, while also increasing the surface area of the polymer. In contrast the hydrophobic DDT in entry 7 may lead to the chain ends contracting away from the aqueous phase, making the chain ends less accessible to the lipase while also reducing the surface area of the polymer. Furthermore, when degraded, TG will produce a soluble degradation product and will contribute to the mass loss. However, DDT is insoluble which will produce an insoluble degradation product which will not contribute to the mass loss and hence, will reduce the observed mass lost due to degradation by comparison.

[0326] Two main conclusions can be drawn from the degradation studies as described above.

[0327] Firstly, although the extent of degradation varied, for all entries in the table above significant degradation occurred such that the polymer products were all effectively broken down. It should be noted that these experiments relate to a specific set of conditions for a limited (ten day) time period: under industrially relevant or commercially relevant conditions, for various different time periods, the degradation may be significantly greater.

[0328] Secondly, the exact behaviour and properties of the polymers can be tailored, in a controllable way, by the choice of monomers, CTAs, polymerisation conditions and other variables. The present invention therefore allows considerable control and consequent benefits in preparing useful polymers.

[0329] Whilst the degradation is exemplified herein with reference to lipases, the products are also degradable under other conditions, for example using other kinds of enzymes (e.g. cutinases) and other conditions in which ester cleavage occurs.

[0330] Breakdown of the polymers by cleavage at the cleavable sites (e.g. esters) may occur under enzymatic or non-enzymatic conditions, for example by hydrolysis under natural or environmental conditions, or under various chemical conditions wherein the nature of the conditions (e.g. pH conditions) may be varied according to the requirements.

Example 27—Further Types of Poly(Caprolactone) Dimethacrylate (PCLDMA) Macromonomer

[0331] The PCLDMA macromonomers described above contain multiple ester linkages grown from a benzene dimethanol initiator.

[0332] Other macromonomers may be used, including those using different diols (including commercially available diols) as initiators. The following example starts from bifunctional caprolactone and accordingly the initiator residue does not contain any aryl groups.

[0333] PCLDMA Synthesis

[0334] In a typical experiment, 150 g of PCL-diol (commercially available, Merck; Mn≈1250 g/mol; 0.12 mol; 1 equivalent) were dissolved in anhydrous DCM (200 mL) in a 1 L round bottom flask. Anhydrous TEA (45 mL; 0.3 mol; 2.5 equivalents) was added, under nitrogen flow, to the solution and the flask was placed in an ice bath. Methacryloyl chloride (30 mL; 0.3 mol; 2.5 equivalents) was then added dropwise over 20 minutes with a syringe under nitrogen flow. Once the addition was complete, the nitrogen flow was turned off, the ice bath removed and the flask left to stir at room temperature for ca. 12 hours. The flask was left under nitrogen atmosphere but open to atmospheric pressure via an oil bubbler in order to prevent any possible pressure built-up.

[0335] The solution was then filtered and washed 3 times with distilled water via liquid/liquid extraction. The organic phase was dried with Na.sub.2SO.sub.4, filtered and then concentrated with a rotary evaporator. The PCLDMA solution in DCM was precipitated into cold petroleum ether containing a small amount of 4-methyloxy phenol anti-oxidant. The precipitate (PCLDMA.sub.1250 macro-monomer) was collected, pre-dried via trituration under compressed air and finally dried under vacuum at room temperature for ca. 6 hours.

[0336] The PCLDMA macro-monomer was then characterised by TD-SEC and .sup.1H NMR.

[0337] PCL-diol was also commercially available with a molecular weight Mn≈2000 g/mol. The macro-monomer PCLDMA.sub.2000 was synthesised in a similar manner to the experiment described above using PCL-diol Mn≈2000 g/mol.

Example 28—Copolymerisation of Degradable Divinyl Monomer (PCLDMA) with Monovinyl Monomer which can be Functionalised (Glycidyl Methacrylate)

[0338] As exemplified above, PCLDMA monomers can be homopolymerized.

[0339] Alternatively they can be copolymerised with other monomers. One reason for doing this is to incorporate certain types of functionality which can be reacted further, e.g. cured.

[0340] In the following example PCLDMA (prepared as above starting from PCL diol) was copolymerised with glycidyl methacrylate (GlyMA), an epoxide-containing monovinyl monomer.

[0341] Poly(PCLDMA-Co-GlyMA) Synthesis

[0342] In a typical experiment, 1.1579 g of DDT (0.78 mmol; 1 equivalent), 1 g of PCLDMA (Mn≈2000 g/mol; 0.47 mmol; 0.6 equivalent), 0.06655 g of GlyMA (0.47 mmol; 0.6 equivalent), 3.5 mg of AIBN (0.027 equivalent) and 1.36 mL of ethyl acetate were placed in a round bottom flask. The solution was degassed via nitrogen sparge for 15 minutes and then placed in a heated mantle at 70° C. for 24 hours. The solution was then cool down to room temperature and precipitated in cold petroleum ether. The precipitate -Poly(PCLDMA-co-GlyMA)- was collected and dry under vacuum at 40° C. for ca. 12 hours. The product was characterised by TD-SEC and .sup.1H NMR.

TABLE-US-00037 CTA Monomer .sup.1H NMR Triple detection SEC (mole DVM (mole Vinyl Mw Mn Entry eq.) (mole eq.) eq.) conversion (Kg/mol) (Kg/mol) MH a 1 DDT PCLDMA.sub.1250 GlyMA >99% 17.6 3.8 4.67 0.397 (1) (0.6) (0.6) 2 DDT PCLDMA.sub.2000 GlyMA >99% 340.4 70.2 4.85 0.395 (1) (0.6) (0.6) 3 DDT PCLDMA.sub.2000 GlyMA >99% 221.3 69.8 3.17 0.303 (1) (0.6) (0.35)

Example 29—Curing of Poly(PCLDMA-Co-GlyMA)

[0343] In a typical experiment, poly(PCLDMA-co-GlyMA) was dissolved in a sebacic acid/THF solution with different epoxy/acid composition (typically ½ or 1/10). After stirring for ca. 2 hours, the homogeneous solution was concentrated, placed on a glass slide, left to dry until all THF was evaporated and finally cured at 150° C. for ca. 2.5 hours. The resulting materials were insoluble in common organic solvents. FIG. 24 shows one of the insoluble cured caprolactone dimethacrylate polymer products.

[0344] Acids other than sebacic acid may be used, for example other multifunctional carboxylic acids (di-acids, tri-acids, tetra-acids etc.).

Example 30—Degradation Study of Cured Poly(PCLDMA-Co-GlyMA)

[0345] Samples of the cured materials were collected from the glass slides and placed in pre-weighed vials containing a solution of lipase (pseudomonas cepacian) in a buffered phosphate saline solution (pH 7.2) with sodium azide (0.02 wt %) at 37° C. with constant agitation for 10 days. The clear homogeneous aqueous phase was then carefully removed from the vials ensuring all solids were kept inside. The vials and solids were then washed with deionised water and the aqueous phase removal procedure was repeated. The vials and their content were then placed in a vacuum oven at 50° C. for 24 hours and the mass loss was assessed by weight difference. The results of the degradation study are gathered in the table below.

TABLE-US-00038 10 days in Lipase solution Weight Total Weight Weight of vial weight of Poly(PCLDMA.sub.2000) of Weight and after 24 polymer Weight of molecular weight empty of polymer hours in left in polymer % loss Mw (kg/mol) @ vial polymer @ t = 0 the vac the vial degraded of Entry epoxy/acid ratio (g) (g) (g) oven (g) (g) (g) polymer 1 221.3 @ ½ 10.4979 0.0281 10.526 10.5121 0.0142 0.0139 49.5 2 221.3 @ 1/10 10.7044 0.0387 10.7431 10.7248 0.0204 0.0183 47.3 3 340.4 @ 1/10 10.4318 0.0352 10.467 10.4536 0.0218 0.01344 38.1

[0346] Thus it can be seen that the present invention can be used not only to make materials (e.g. ester-based materials) which are degradable, but also (when for example functionality is introduced to permit curing) to make such materials in the form of insoluble resins.

[0347] In many contexts the present invention is useful as it allows the preparation of soluble processable materials, but in other contexts insoluble resins are useful, and therefore it is beneficial that the present invention allows both possibilities.

[0348] One skilled in the art will therefore recognize that the present invention applies to both thermoplastic materials and thermoset materials. Thus, the polymer of the first aspect of the present invention may be a thermoplastic polymer, and polymers when further reacted e.g. cured may be thermoset polymers.

Example 31—Degradable Trivinyl Monomers

[0349] Analogous to PCLDMA methodology exemplified above, degradable monovinyl monomers of tri- and higher functionality may also be prepared and used to make degradable branched polymers. The following example relates to polycaprolactone trimethacrylate (PCLTMA) macromonomers.

[0350] PCLTMA Synthesis

[0351] In a typical experiment, 20 g of PCL-triol (commercially available, Merck; Mn ca 300 g/mol; 0.0667 mol; 1 equivalent) were dissolved in anhydrous DCM (100 mL) in a 1 L round bottom flask. Anhydrous TEA (33 mL; 0.233 mol; 3.5 equivalents) was added, under nitrogen flow, to the solution and the flask was placed in an ice bath. Methacryloyl chloride (23 mL; 0.233 mol; 3.5 equivalents) was then added dropwise over 20 minutes with a syringe under nitrogen flow. Once the addition was complete, the nitrogen flow was turned off, the ice bath removed and the flask left to stir at room temperature for ca. 12 hours. The flask was left under nitrogen atmosphere but open to atmospheric pressure via an oil bubbler in order to prevent any possible pressure built-up.

[0352] The solution was then filtered and washed 3 times with distilled water via liquid/liquid extraction. The organic phase was dried with Na.sub.2SO.sub.4, filtered and then concentrated with a rotary evaporator to yield polycaprolactone trimethacrylate (PCLTMA). The PCLTMA solution in DCM was precipitated into cold petroleum ether containing a small amount of 4-methyloxy phenol anti-oxidant. The precipitate (PCLTMA macro-monomer) was collected, pre-dried via trituration under compressed air and finally dried under vacuum at room temperature for ca. 6 hours.