Biodegradable Thermoplastic Elastomers Incorporating POSS: Synthesis, Microstructure, and Mechanical Properties

A need exists for biodegradable thermoplastic elastomers with tailorable mechanical and degradation properties. Toward meeting this need, we introduce a family of biodegradable thermoplastic elastomers that feature soft segments based on caprolactone-d,l-lactide or caprolactone-glycolide copolymers of low crystallinity, combined with a POSS-based hard segment with relatively low melting transition. Molecular characterization of the polyols and polyurethanes indicates good control over the composition and molecular weights, with high molecular weights for the polyurethanes, as desired. Thermal, mechanical, and microstructural characterization enabled establishment of structure-property relationships. Incorporation of two different comonomers was effective in diminishing soft segment crystallinity, positively impacting elasticity, while increasing POSS content proved effective in establishing thermally robust elastic behavior as well as mechanically reinforcing the polyurethanes. Prestraining the new thermoplastic elastomers was found to positively impact elasticity, which we attribute to enhancement of phase separation of the two blocks with support from thermal and X-ray diffraction studies.