Please use this identifier to cite or link to this item: http://scholarbank.nus.edu.sg/handle/10635/22481
Title: Designing and Synthesis of Shape-Memory Polymers for Biomedical Application
Authors: XUE LIANG
Keywords: shap-memory polymers, poly(caprolactone), biodegradable, self-expandable stent, drug-eluting stent, star polymer
Issue Date: 17-Aug-2010
Source: XUE LIANG (2010-08-17). Designing and Synthesis of Shape-Memory Polymers for Biomedical Application. ScholarBank@NUS Repository.
Abstract: Shape-memory polymers (SMPs) can change their shapes in a predefined way when exposed to an external stimulus. Among these, segmented polyurethanes (SMPUs) have gained the greatest attention due to the very unique properties, such as biocompatibility, biodegradability and vast possibilities for synthesis. In addition, SMPUs display remarkable shape-memory properties due to the phase separation between two incompatible segments, which brings about properties related to blood compatibility and biodegradability. For this reason, SMPs made from polyurethanes have a great potential in biomedical applications. Moreover, the microphase separation in SMPUs system facilitates thermal activation of shape-memory effect. Although the usage of SMPUs offers desirable properties, it also suffers from several challenges. The material experiences a dimensional instability after processing, thus resulting in insufficient recovery stress, long recovery time and in some cases low value of shape-fixity rate as well as the transition temperature (Ts) higher than body temperature. In this work, we aim to design and synthesize biocompatible and biodegradable star SMPs with desired properties and shape-change at body temperature for the potential application as implants. Firstly, star block-copolymer containing three-arm poly(¿-caprolactone) (PCL) as biodegradable switching-segment and polyurethane as hard-segment was developed, showing shape-memory effect at 37 oC with shape-recovery in 10s, shape-fixity-rate (Rf) of 91-92% and shape-recovery-rate (Rr) of 95-99%. Secondly, new block-copolymer containing poly(3-hydroxybutyrate-co-3-hydroxyvalerate) as hard-segment and hyperbrached PCL as switching-segment were prepared as a safe biomaterial with good mechanical properties, exhibiting Ts at 40 oC with Rf of 94% and Rr of 98%. SMP was used, for the first time, as stent with complete self-expansion at 37 oC within 25 s. Finally, block-copolymer containing hyperbrached PCL and poly(2-oxepane-1,5-dione)-diol as new hard segment. This material was non-cytotoxic, displayed better mechanical and shape-memory properties, and was used as self-expandable drug-eluting stent, allowing for the controlled release of paclitaxel in a sustained manner.
URI: http://scholarbank.nus.edu.sg/handle/10635/22481
Appears in Collections:Ph.D Theses (Open)

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