Self-Reinforced Polymer Gels Using Strain-Induced Crystallization

Abstract

Tough polymer gels are required for various applications such as soft actuators/sensors, and artificial tendons/ligaments. For these applications, the polymer gels should show reversible mechanical responses under repeated high stress at a high frequency (ex. 1 Hz). Recently, we have successfully developed tough and instantly recoverable polymer gels utilizing strain-induced crystallization (SIC). In order to realize SIC in polymer gels, the polymer chain orientation under stretching should be homogeneous. We have discovered that SIC occurs in slide-ring (SR) hydro and ion gels with slidable cross-links, tri-branched PEG gels, and Tetra-branched PEG gels. From in-situ wide-angle X-ray scattering (WAXS) experiments on the gels under repeated tensile deformation, we found that crystalline domains of PEG form at a large strain and destructs quickly when applied stress is reduced. The reversible strain-induced crystallization yields the high toughness and instant recoverability.