Transparent, thermoplastic, aliphatic polyesters through crystallization under molecular confinement

Abstract

•We report segmented polyesters with nanoscale crystalline poly(L-lactic acid) domains •Polymers possess high modulus and elongation at break and can be melt processed •Solution processing yields transparent films that are degradable and cytocompatible •Films can be bonded by plasma activation and undergo infrared-activated shape change In semi-crystalline biodegradable polymers, uncontrolled evolution of crystallinity impacts processing and bulk properties, limiting their application. Through molecular confinement of low-molecular-weight poly(L-lactic acid) (PLLA) segments by polysiloxane blocks and processing at far-from-equilibrium conditions, PLLA crystallization into lamellae of a few nm in thickness with coherence lengths below 100 nm was achieved, thus giving access to films that are optically transparent for over 5 years, possess high Young’s modulus and elongation at break, undergo controlled degradation, and support functional endothelialization. The films possess a nanophase segregated bulk morphology with a hydrophobic siloxane-dominated surface that can be pressure bonded following cold oxygen plasma activation and low-temperature glassy PLLA domains interspersed by nanoscale crystalline physical crosslinks that enable glass transition temperature-triggered shape change. The segmented thermoplastic polyesters (STEPs) can additionally be processed using melt-extrusion printing into 3D objects, thus opening potential application opportunities in the fabrication of implantable/degradable electronics, smart textiles, and packaging. In semi-crystalline biodegradable polymers, uncontrolled evolution of crystallinity impacts processing and bulk properties, limiting their application. Through molecular confinement of low-molecular-weight poly(L-lactic acid) (PLLA) segments by polysiloxane blocks and processing at far-from-equilibrium conditions, PLLA crystallization into lamellae of a few nm in thickness with coherence lengths below 100 nm was achieved, thus giving access to films that are optically transparent for over 5 years, possess high Young’s modulus and elongation at break, undergo controlled degradation, and support functional endothelialization. The films possess a nanophase segregated bulk morphology with a hydrophobic siloxane-dominated surface that can be pressure bonded following cold oxygen plasma activation and low-temperature glassy PLLA domains interspersed by nanoscale crystalline physical crosslinks that enable glass transition temperature-triggered shape change. The segmented thermoplastic polyesters (STEPs) can additionally be processed using melt-extrusion printing into 3D objects, thus opening potential application opportunities in the fabrication of implantable/degradable electronics, smart textiles, and packaging.