Triple Shape Memory Materials Incorporating Two Distinct Polymer Networks Formed by Selective Thiol–Michael Addition Reactions

Abstract

We present a composite material composed of dual polymer networks uniquely formed from a single reaction type and catalyst but involving monomers with dramatically different reactivities. This powerful new approach to creating polymer networks produces two narrow glass transition, homogeneous networks sequentially from a single reaction but with all monomers present and uniformly mixed prior to any polymerization. These materials exhibit a triple shape memory effect based on the dual polymer networks, which were both formed using the thiol–Michael addition reaction. Two multifunctional thiol monomers (i.e., mercaptoacetate (MA) and mercaptopropionate (MP)) and two multifunctional vinyls (i.e., vinyl sulfone (V) and acrylate (A)) were polymerized in situ using a nucleophilic initiator. The MA-V polymer network (Tg = 55 °C) was generated first associated with the higher functional group reactivities followed by the formation of the MP-A network (Tg = 10 °C) which was confirmed by FT-IR, SEM, DMA, and a sepa...