Liquid crystalline elastomers (LCEs) are functional materials whose stimuli-response is strongly influenced by mechanical properties dependent on the development of the polymer network. These networks are commonly fabricated by subjecting acrylate monomers to polymerization reactions with thiols. This work explores the network structure and properties as a result of LCE polymer networks formed via radical-mediated photopolymerization reactions using diacrylate liquid crystalline monomers with dithiols. Control experiments contrasting these reactions to conventional thiol-acrylate photopolymerizations in non-liquid crystalline media indicate that the liquid crystalline structural character strongly hinders mobility of reactive species during the formation of the LCE polymer network. Detailed analysis using monoacrylates indicates that these reactions produce LCEs composed of singly-reacted dithiols and numerous dangling ends in the structure.  The unreacted thiol end of the dithiols incorporated in the LCE polymer network is utilized to facilitate post-functionalization of the LCE with reactive additives for additional degrees of control of functional material properties.

Thiol-acrylate chain transfer polymerization to prepare and functionalize liquid crystalline elastomers

ACS Spring 2022

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