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

Abstract

This work demonstrates that neat polystyrene-blockpoly(ethylene-co-butylene)-block-poly styrene (SEBS) displays thermally responsive shape memory properties. The shape memory properties were quantitatively investigated under uniaxial tension using a dynamic mechanical analyzer and manual stretching. The shape memory properties of SEBS were found to depend on both the molecular weight of the polymer and on the shape programming conditions, including the programming temperature, applied strain, and annealing time at elevated temperature under load. The shape memory mechanism is proposed to be a result of partial stress relaxation of the block copolymer network under load and the formation of a second network with a lower glass transition temperature. This second network counterbalances the initially stretched network producing fixity and weakens first on heating, allowing recovery. Due to the unique mechanism of shape memory where the secondary network is generated from the initial network, achieving higher fixity generally occurs at the expense of high recovery and vice versa.

Triblock polyester thermoplastic elastomers with semi-aromatic polymer end blocks by ring-opening copolymerization

“…High-performance elastomers showing enhanced heat resistance, higher resilience and extensibility would be useful for applications as electrolytes, nanoporous membranes, thin lm lithography, stretchable optical bres and shapememory materials. [7][8][9] TPEs are typically ABA-type block copolymers, where 'B' is a so rubbery material, with a glass transition temperature (T g ) below room temperature, that bridges between hard-glassy or semi-crystalline outer 'A' blocks, showing T g or T m values above room temperature. 2 When the relative volume fractions of A and B are optimized, microphase separation of the blocks may occur yielding hard domains located within the so matrix.…”

Thermo‐responsive shape memory behavior of poly(styrene‐b‐isoprene‐b‐styrene)/ethylene‐1‐octene copolymer thermoplastic elastomer blends

“…On the other hand, the blends also exhibited lower R r values than those obtained from DMA device. It may be ascribed to the stress relaxation in the SIS phase by pulling‐out of the polystyrene molecules at high strain, which may cause the higher permanent deformation 28 in the high strain application. The stress relaxation may have caused a reduction in retracting force that drives the recovery process in the blend which can also be a reason for the decreased R r values 28 .…”

“…It may be ascribed to the stress relaxation in the SIS phase by pulling‐out of the polystyrene molecules at high strain, which may cause the higher permanent deformation 28 in the high strain application. The stress relaxation may have caused a reduction in retracting force that drives the recovery process in the blend which can also be a reason for the decreased R r values 28 . In this application, the optimum R f and R r values were determined as 78.67% and 90% for shape memory process of the 60PEO/40SIS blend.…”

“…The stress relaxation may have caused a reduction in retracting force that drives the recovery process in the blend which can also be a reason for the decreased R r values. 28 In this application, the optimum R f and R r values were determined as 78.67% and 90% for shape memory process of the 60PEO/40SIS blend. The video record of the recovery process of 60PEO/40SIS is given as a supporting file (Video 1).…”

Stimuli‐responsive mechanical properties in polymer glasses: challenges and opportunities for defense applications

“…[149][150][151][152][153] Traditional block copolymers like poly[styrene-block-(ethylene-cobutylene)] have also been used to impart thermal responsivity by stressing one phase over the other lower T g phase. 154 It is then expected that other phase-separated polymers may have shape memory properties, but have not been evaluated as such.…”