Toward Sustainable and Strong ABA‐Type Thermoplastic Elastomers with Poly(ε‐Caprolactone‐co‐4‐Methyl‐ε‐Caprolactone) Soft Midblock and Polystyrene Hard End Blocks

An array of ABA‐type thermoplastic elastomers (TPEs), that is, poly(styrene‐b‐(ε‐caprolactone‐co‐4‐methyl‐ε‐caprolactone)‐b‐styrene) (SCSs), with controlled molecular weights and narrow distributions, are synthesized by ring opening copolymerization of 4‐methyl‐ε‐caprolactone and ε‐caprolactone and subsequent atom transfer radical polymerization of styrene. Thermal and mechanical analyses indicate that the molecular weights of middle and end blocks have significant effect on both the thermal and mechanical performances. It is worth noting that the target polymer SCS(155, 0.33) shows tensile strength of up to ≈42 MPa and impressive ultimate elongations of up to 1100% which is much higher than common styrenic TPEs. Additionally, SCS(155, 0.33) also displays an elastic recovery value of 91.5% after 19 stress‐strain cycles, suggesting that a good elastic recovery property therein.