Highly Stretchable Fatty Acid Chain-Dangled Thermoplastic Polyurethane Elastomers Enabled by H-Bonds and Molecular Chain Entanglements

Abstract

Thermoplastic polyurethane (TPU) elastomers are widely used in daily products owing to their flexible structures and decent mechanical properties. Vegetable oils (VOs) are promising renewable resources for polymer synthesis with readily availability and abundant derivatives. However, most VO-based polyurethanes are usually thermosets with an unsatisfactory material performance because the C═C bonds are randomly located on triglyceride long chains. Herein, a biobased TPU elastomer was facilely synthesized from palm oil (PO) with desirable and tunable mechanical properties. PO-based diol was synthesized from PO via amidation with 2-(2-hydroxyethylamino)ethanol. The resulting PO diethanolamide (POEA), combined with biobased butane-1,4-diol, was further reacted with 1,6-diisocyanatohexane to prepare PO-based TPU elastomers. The elastomers containing abundant H-bonds from carbamates in the backbone and dangling fatty acid side chains exhibited a microphase separation structure, endowing the elastomers with superior stretchability (up to a strain of 831%), restorability, and self-healing ability. The morphological, melting, crystallization, and rheological behaviors of the elastomers were fully studied. The dynamic and reversible three-dimensional cross-linked network consisting of van der Waals forces and H-bonds was investigated to reveal the formation mechanism of the elastomers.