A structural reconsideration: Linear aliphatic or alicyclic hard segments for biodegradable thermoplastic polyurethanes?

Abstract

Thermoplastic polyurethane elastomers (TPUs) with a biodegradable chain extender and different nonaromatic diisocyanate hard segments were synthesized and tested concerning their thermal, mechanical, and degradation properties and for their processability regarding electrospinning. The design of the TPUs was based on the structural modification of the hard segment using linear aliphatic hexamethylene diisocyanate (HMDI), more rigid alicyclic 4,4′-methylene bis(cyclohexylisocyanate) (H12MDI), 1,3-bis(isocyanatomethyl)cyclohexane (BIMC), or isophorone diisocyanate (IPDI). The soft segment consisted of poly(tetrahydrofuran). Bis(2-hydroxyethyl) terephthalate (BET) was used as chain extender with cleavable ester bonds. Some of the polyurethanes based on alicyclic diisocyanate showed better mechanical performance than the less rigid HMDI-based TPU. The TPU in vitro degradability was tested for 25 days at elevated temperatures in PBS buffer and indicated a bulk erosion process. Electrospinning experiments were conducted and promising results with respect to further applicability of these materials in vascular tissue engineering were obtained.