Thermoresponsive Semicrystalline Poly(ε-caprolactone) Networks: Exploiting Cross-linking with Cinnamoyl Moieties to Design Polymers with Tunable Shape Memory

Abstract

The overall goal of this study was to synthesize semicrystalline poly(ε-caprolactone) (PCL) copolymer networks with stimuli-responsive shape memory behavior. Herein, we investigate the influence of a cinnamoyl moiety to design shape memory polymer networks with tunable transition temperatures. The effect of various copolymer architectures (random or ABA triblock), the molecular weight of the crystalline domains, PCL diol, (M(w) 1250 or 2000 g mol(-1)) and its composition in the triblock (50 or 80 mol %) were also investigated. The polymer microstructures were confirmed by NMR, DSC, WAXS and UV-vis spectroscopic techniques. The thermal and mechanical properties and the cross-linking density of the networks were characterized by DSC, tensile testing and solvent swelling, respectively. Detailed thermomechanical investigations conducted using DMA showed that shape memory behavior was obtained only in the ABA triblock copolymers. The best shape memory fixity, R(f) of ~99% and shape recovery, R(r) of ~99% was obtained when PCL diol with M(w) 2000 g mol(-1) was incorporated in the triblock copolymer at a concentration of 50 mol %. The series of triblock copolymers with PCL at 50 mol % also showed mechanical properties with tunable shape memory transition temperatures, ranging from 54 °C to close to body temperature. Our work establishes a general design concept for inducing a shape memory effect into any semicrystalline polyester network. More specifically, it can be applied to systems which have the highest transition temperature closest to the application temperature. An advantage of our novel copolymers is their ability to be cross-linked with UV radiation without any initiator or chemical cross-linker. Possible applications are envisioned in the area of endovascular treatment of ischemic stroke and cerebrovascular aneurysms, and for femoral stents.

Polymeric Shape-Memory Micro-Patterned Surface for Switching Wettability with Temperature

“…As PCO is a thermally induced shape memory polymer, where the transition temperature corresponds with the melting temperature (Tm), a cyclic thermomechanical experiment was designed in the stress-controlled mode according to Garle et al [29] in order to evaluate the shape memory behavior. Only the crosslinked sample (PCO+2%DCP) was studied by this technique as raw PCO sample flows like a viscous liquid above the melting temperature and does not demonstrate shape memory capabilities.…”

Biodegradable polyester-based shape memory polymers: Concepts of (supra)molecular architecturing

“…Crosslinkable functional groups may appear as end or side groups, and even in the main macromolecular chains. Garle et al [27] modified PCL homo-and copolymers by cinnamate compound. The UV crosslinkable cinnamoyl side groups resulted in a crosslinked gel content of about 70 wt%.…”

Connecting free volume with shape memory properties in noncytotoxic gamma‐irradiated polycyclooctene

“…34 However, when the force is maintained constant, deformation diminishes. 24 Furthermore, as the applied force is considerable low (1 N), the polymer partially recovers the undergone strain.…”