Body temperature triggered shape‐memory polymers with high elastic energy storage capacity

Abstract

Shape‐memory polymers (SMPs) that respond near body temperature are attracting broad interest, especially in the biomedical fields. In this study, the triggering temperature of poly(caprolactone) SMP networks is precisely adjusted by inclusion of non‐crystallizable molecular linkers and by variation of prepolymer molecular weight. Longer, non‐crystalline linkers and lower molecular weight prepolymers interfere with crystallization, lowering the transition temperature. Networks are prepared with crystallization temperatures that are beneath the human body temperature and yet are above room temperature. Upon cooling such amorphous networks to room temperature, crystallization is sluggish. There, elastomers can be easily strained by several hundred‐percent to induce crystallization, thereby fixing strained states. If subsequently heated, programmed SMPs can release significant amounts of stored strain energy (∼3 MJ/m3). SMPs that combine elastic energy storage and exhibit triggering temperatures near the human body temperature could benefit emerging applications in the biomedical space. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 1397–1404

A novel shape memory poly(ε-caprolactone) network via UV-triggered thiol-ene reaction

“…Upon cooling samples to the room temperature with removal of applied stress, the newly formed crystallites induced by strain in the amorphous PCL part, together with realignment and re‐crystallization of the existed crystallites, stabilized the temporary shape in deformed state . The increase of crystallinity was confirmed through XRD analysis (Fig.…”

“…The covalent bonding between PCL arm and SiO 2 core gave rise to more positional restriction to reduce melt entropy of crosslinked PCL compared with their linear analogues, which caused the enhanced melting temperature. It is very useful to explore the relationship between melting transition point and the molecular weight of pre‐polymer as well as the network structures, from which Anthamatten's group had designed body temperature triggered shape‐memory polymers . The network structural designs also have an evident effect on the melting transition.…”

Polysulfone‐Based Shape Memory Thermoplastics with Body Temperature Triggering

“…Thermally induced shape memory polymers (SMPs) are an important class of smart materials which can switch their shape in a predefined way to respond to an external stimulus . There has been significant interest to develop SMPs for the last two decades, especially for the ones that can be triggered by body temperature due to their great potential for biomedical applications such as cardiovascular stents, implants, self‐healing coatings, actuators, and tissue engineering . SMPs generally consist of two components: a hard segment formed by chemical or physical cross‐linking that constitutes the permanent phase, and a soft segment that provides the temporary shape below transition temperature ( T trans ) .…”

“…Therefore, design of SMPs with suitable components for desired applications remains a challenge. Until now, researchers have mainly focused on copolymers of poly(lactide), poly(glycolide) and poly(ε‐caprolactone) and polyurethane to obtain SMPs that can be triggered around the body temperature …”

Preparation of Biodegradable and Elastic Poly(ε-caprolactone-co-lactide) Copolymers and Evaluation as a Localized and Sustained Drug Delivery Carrier

“…PCL is a semicrystalline material displaying rubbery properties, whereas PLA is a crystalline, hard, and brittle material [13,14,15,16,17]. Their PC x L y A copolymer is an attractive replacement for medical applications because of its controllable elasticity and the capacity to change the ε-caprolactone/ l -lactic molar ratios and their mechanical properties.…”