The synthesis of biodegradable polymers with functional side chains

Abstract

Trifunctional hydroxy‐terminated oligomeric polyesters, Mn 500, 1000, and 2000, were prepared by initiating ring‐opening copolymerization of δ‐valerolactone and ε‐caprolactone with glycerol. The prepolymers were converted to crosslinked polyester‐urethanes by their reaction with hexane‐1,6‐diisocyanate in proportions corresponding to 70, 80, 90, and 100% of the hydroxyl content. The moduli of the resulting elastomers varied between 0.12 MPa and 3.83 MPa, and the elongation at break between 60 and 2000%. The residual hydroxyl groups were derivatized by heterogeneous reaction with chloroacetic anhydride or excess hexane‐1,6‐diisocyanate, and these and further transformations of the functional groups were verified by infrared spectroscopy and electron probe x‐ray microanalysis. A second series of hydroxy‐substituted elastomers was synthesized by copolymerization of δ‐valerolactone, ε‐caprolactone, and 4‐(t‐butyldimethylsilyloxy)‐ε‐caprolactone, using different amounts of 2,2‐bis(caprolacton‐4‐yl)propane as the crosslinking agent; removal of the t‐butyldimethylsilyl group to liberate pendant hydroxyl groups was achieved with acetic acid but not fluoride ion. The hydroxylated polyester (but not the polyesterurethanes) was shown to undergo enzymatic surface erosion in rabbit. The biodegradation data were compared with results previously obtained with low‐modulus elastomeric polyesters.

Biodegradable polyurethanes for implants. II. In vitro degradation and calcification of materials from poly(ϵ‐caprolactone)–poly(ethylene oxide) diols and various chain extenders

“…The polyurethanes obtained in this study had the projected chemical compositions (the ratio of hydrophilic segments to hydrophobic segments) and molecular weights comparable to those of experimental and commercial materials. [1][2][3][20][21][22][23][28][29][30][31][34][35][36] Their molecular weights were independent of the catalyst used. The changes in the IR spectra suggest that a higher concentration of hydrogen bonding developed in the polymers with a higher concentration of the hydrophilic component.…”

“…[20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] Such moieties can be based on diols of lactic acid with ethylene diol or diethylene diol, 20 lactic acid and 1,4-butanediol, 32 or butyric acid and ethylene diol. 33 Degradable polyurethanes can also be obtained from monomers containing peptide links; 21,23,24 sugar derivatives; 22,28,30,31 the hydroxy-terminated copolymers L-lactide--caprolactone, glycolide--caprolactone, 25 -caprolactone-co-␦-valerolactone, 26,36 lysine diisocyanate, 25,27,29 poly(ethylene oxide) (PEO), and poly(-caprolactone) (PCL); and amino acid-based chain extenders. 34 This work investigates the degradation and calcification in vitro of experimental linear and biodegradable poly(ester urethane)s and poly(ester ether urethane)s with various hydrophilic-to-hydrophobic ratios for potential applications as tissue adhesion barriers, scaffolds for tissue engineering, and substitutes for cancellous bone grafts.…”

Recent Advances in the Functionalization of Aliphatic Polyesters by Ring-Opening Polymerization

“…[6,7] The protection of the hydroxyl group prior to the Baeyer-Villiger is mandatory because hydroxyoxepan-2-one obtained by reaction of 4-hydroxycyclohexanone is not stable and rearrange into 5-(2-hydroxyethyl)dihydrofuran-2(3H)-one (Scheme 4). [8] γEt 3 SiOεCL was copolymerized with εCL in order to obtain the corresponding statistical copolyesters. [6,7] The deprotection of the hydroxyl group turned out to be difficult even under optimized conditions, especially for copolyesters with a γEt 3 SiOεCL content higher than 50% due to the noxious transesterification reaction of an internal ester by the released hydroxyl group, which results in the formation of a five-membered lactone.…”

Novel Macromolecular Architectures Based on Aliphatic Polyesters: Relevance of the “Coordination-Insertion” Ring-Opening Polymerization

“…Pitt et al [65], and more recently, Albertsson et al [73], have prepared chemically cross-linked aliphatic polyesters by ROP of the corresponding cyclic ester monomers in the presence of γ,Y-bis(ε-caprolactone)-type comonomers (Scheme 17). The cross-linked films displayed different swelling behaviors, de-gradability, and elastomeric properties depending on the nature of the lactone and composition of the comonomers feed.…”