Mechanically Tough Noncovalent-Bonded Block Polymer-Based Thermoplastic Elastomers

At room temperature, block polymers with hard polymer chains in a glassy or crystalline state (hard segments) and soft polymer chains in a molten state (soft segments) exhibit elastomeric behavior (rubber elasticity). When heated, the entire material melts and flows; however, it regains its rubber elasticity upon cooling. Therefore, these block polymer materials are called thermoplastic elastomers (TPEs). The demand for TPEs continues to grow because of their excellent processability; nevertheless, there is increasing demand for TPEs with superior mechanical properties. Therefore, we investigated noncovalent-bonded block polymer-based TPEs. This review first presents our studies on the synthesis and mechanical properties of poly(4-vinylpyridine)-b-poly(butyl acrylate-co-acrylamide)-b-poly(4-vinylpyridine) and polystyrene-b-poly(butyl acrylate-co-acrylamide)-b-polystyrene triblock copolymers, which are pioneering TPEs with noncovalent bonding groups incorporated into the soft segments. We then review our development of toughened styrenic TPEs with noncovalent bonding groups incorporated into a polyisoprene block of the commercially available polystyrene-b-polyisoprene-b-polystyrene (SIS). Finally, we introduce the application of noncovalent-bonded SIS as an adhesive additive.