Dynamic crosslinked poly(styrene-block-butadiene-block-styrene) via Diels-Alder chemistry: An ideal method to improve solvent resistance and mechanical properties without losing its thermal plastic behavior

Poly(styrene-block-butadiene-block-styrene) (SBS) is a typical example of thermal plastic elastomers (TPE). People usually encounter a well-known paradox for SBS, where improving its poor solvent resistance and low mechanical properties usually means it suffers from losing its thermal plastic remolding ability, one of most important characters for TPE. In this paper, we propose a novel solution for this problem. SBS was first modified with furan via a thiol-ene reaction and then reacted with bismaleimide to form thermally dynamic reversible crosslinking linkages for SBS via a Diels-Alder reaction. As a result, the dynamic crosslinked SBS could only swell in the toluene with improved solvent resistance at ambient temperature. The mechanical properties showed great improvement. As an example, the maximum tensile strength was obtained at 14.96 MPa, increased by almost 8 times in comparison with the pure SBS and the tensile strain was still kept above 800%. More importantly, the crosslinked SBS could still be thermal plastic remolded due to the de-crosslinking reaction via a retro-DA reaction at higher temperature and the mechanical properties still remained almost the same even after 3 generations of remolding. The merits of this modified SBS originate from its dynamic crosslinking network to improve its mechanical properties and solvent resistance without sacrificing its thermal plastic remolding ability.