Polyurethane elastomers with amphiphilic ABA tri-block co-polymers as the soft segments showing record-high tensile strength and simultaneously increased ductility

Abstract

Increasing the strength while not sacrificing the ductility of polymeric elastomers helps in expanding the application range and this meanwhile improves the durability of the materials. However, compromise on the strength or ductility usually occurs because the regulation rules for the two attributes are mutually exclusive. In this work, we report the first leverageable strategy for preparing polyurethane elastomers that can show record-high tensile strength and uncompromising ductility. The polyurethanes are prepared with ABA tri-block co-polymers as the soft segments, where A represents a polyester end block showing miscibility with the urethanes, while B is a middle polymer block showing great immiscibility with the urethanes. It is confirmed that this deliberately adjusted amphiphilicity of the soft segments triggers the formation of small and uniform hard domains that demonstrate an intriguing mechano-responsive orientability under uniaxial deformation. In this way, the polymer chains can be highly stretched and aligned to form nanofibril-like structures, and meanwhile the oriented polymer chains in the same direction can cooperatively resist the external loading stress, making the polyurethanes extraordinarily ductile and strong. Specifically, when poly(ε-caprolactone)-block-poly(ethylene glycol)-block-poly(ε-caprolactone) was used as the soft segment, a polyurethane with a record-high tensile strength and a remarkably increased ductility at the same time was obtained. When the strategy was extended to modify poly(dimethyl siloxane) based polyurethanes, a significant increase in both tensile strength and ductility was also simultaneously achieved.