Shape Memory Properties of Polystyrene-<i>block</i>-poly(ethylene-<i>co</i>-butylene)-<i>block</i>-polystyrene (SEBS) ABA Triblock Copolymer Thermoplastic Elastomers

Abstract

This\nwork demonstrates that neat polystyrene-<i>block</i>-poly­(ethylene-<i>co</i>-butylene)-<i>block</i>-poly styrene (SEBS)\ndisplays thermally responsive shape memory properties.\nThe shape memory properties were quantitatively investigated under\nuniaxial tension using a dynamic mechanical analyzer and manual stretching.\nThe shape memory properties of SEBS were found to depend on both the\nmolecular weight of the polymer and on the shape programming conditions,\nincluding the programming temperature, applied strain, and annealing\ntime at elevated temperature under load. The shape memory mechanism\nis proposed to be a result of partial stress relaxation of the block\ncopolymer network under load and the formation of a second network\nwith a lower glass transition temperature. This second network counterbalances\nthe initially stretched network producing fixity and weakens first\non heating, allowing recovery. Due to the unique mechanism of shape\nmemory where the secondary network is generated from the initial network,\nachieving higher fixity generally occurs at the expense of high recovery\nand vice versa.