Synthesis and Characterization of Random and Triblock Copolymers of -Caprolactone and (Benzylated)hydroxymethyl glycolide

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• 作者：C. A. M. Loontjens ; T. Vermonden ; M. Leemhuis ; M. J. van Steenbergen ; C. F. van Nostrum ; W. E. Hennink
• 刊名：Macromolecules
• 出版年：2007
• 出版时间：October 2, 2007
• 年：2007
• 卷：40
• 期：20
• 页码：7208 - 7216
• 全文大小：149K
• 年卷期：v.40,no.20(October 2, 2007)
• ISSN：1520-5835

文摘

The aim of this study was to develop new polyesters with pendant functional hydrophilic groupssuitable for biomedical applications. Therefore, -caprolactone (CL) was copolymerized with benzyl protectedhydroxymethyl glycolide (BHMG) to introduce, after deprotection, hydroxyl groups into the polyester. Randomand triblock copolymers were synthesized in the melt using benzyl alcohol and tin(II) 2-ethylhexanoate as initiatorand catalyst, respectively, and deprotected by hydrogenation. The synthesized polyesters before and afterdeprotection were characterized by NMR, GPC, and DSC measurements. Mixtures of CL and BHMG werepolymerized at 110, 130, and 150 C. A polymerization kinetics study revealed that BHMG was far more reactivethan CL at the three reaction temperatures investigated. However, due to transesterification reactions, randomcopolymers were formed at 150 C, whereas at 110 C, the copolymers had a more blocky structure. Takingadvantage of this knowledge, ABA triblock copolymers of poly(-caprolactone) (PCL, block B) and poly(benzylprotected hydroxymethyl glycolide) (PBHMG, block A) were synthesized. To this end, , PCL-diols were firstsynthesized at 130 C by melt polymerization of CL initiated with 1,4-butanediol, which were subsequentlychain extended with BHMG at 130 C. Four triblock copolymers with different PCL (from 2.3 to 4.8 kg/mol)and PBHMG (from 2.0 to 4.3 kg/mol) block lengths were synthesized. The random copolymers (before and afterdeprotection) were fully amorphous and had their T_g ranging from -29 to -16 C. Before deprotection, theblocks of the triblock copolymers were fully miscible, while triblock copolymers showed phase separation andwere semicrystalline materials after deprotection. The PCL segments crystallize with a T_m ranging from 39 to 46C. The latter polymers are interesting for tissue engineering applications because they enable the formation ofporous dimensionally stable materials at body temperature.