Design of Soft and Strong Thermoplastic Elastomers Based on Nonlinear Block Copolymer Architectures Using Self-Consistent-Field Theory

Thermoplastic elastomers (TPEs) that are soft at low extension yet strong at large extension are of great importance in a variety of technological applications. In ABA-triblock architectures, both the overall molecular weight and the composition of the glassy A-blocks correlate with TPE strength. The design space of current TPEs based on linear ABA triblock copolymers (e.g., polystyrene- b -polybutadiene- b -polystyrene) is restricted by the accessibility of the order−disorder transition temperature, limiting the molecular weight, and restricted by the maximum volume fraction for which glassy A-blocks will form discrete domains. Using self-consistent-field theory (SCFT), we designed in silico two new, nonlinear TPE architectures that significantly relax the composition restriction: radial (ABA′) n and A(BA′) n miktoarm star-block copolymers with chemically identical, but unequal, molecular weight A-blocks. Through a balance of end-block bidispersity, block extraction from the interface, and architectural asymmetry, these molecular architectures are able to stabilize phases with discrete A-rich domains at remarkably high overall A-monomer compositions ( f A ). In some cases the maximum f A achieved for phases with discrete A-rich domains surpasses twice that of conventional linear ABA TPEs.