Synthesis and characterization of biodegradable, amorphous, soft IPNs with shape-memory effect

Star-shaped oligo[(D,L-lactide)-co-e-caprolactone]s (PCLA) with various number average molecular weights were synthesized via ring-opening polymerization of D,L-lactide (DLLA) and e-caprolactone (CL) with organic Sn as catalyst and pentaerythritol as an initiator. The elastic amorphous interpenetrating polymer networks (IPNs) of polyesterurethane/poly(ethylene glycol) dimethacrylate (PEGDMA) were synthesized in situ by UV-photopolymerization of PEGDMA and thermal polymerization of PCLA with isophorone diisocyanate (IPDI). IPNs are transparent soft materials and the gel content of the IPNs is exceeding 87%. They are rubbery when PEGDMA content is above 10% at room temperature. IPNs show good shape-memory properties. IPNs recover quickly its permanent form in 10 sec when the environment temperature is above its glass transition temperature (Tg). IPNs have only one single Tg between the Tg of PEGDMA and polyesterurethane. The strain recovery rate (Rr) and the strain fixity rate (Rf) are above 90%. No characteristic peaks of PEG crystallites in X-ray diffraction pattern (XRD) demonstrate that they are amorphous polymer networks. The wettability, degradation rate, mechanical properties, and Tg of the IPNs could be conveniently adjusted by changing PEGDMA content in IPNs. The soft IPNs are promising suitable as potential soft substrates with tailored mechanical properties for potential clinical or medical use. Copyright (C) 2011 John Wiley & Sons, Ltd.