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 (T g = 55 °C) was generated first associated with the higher functional group reactivities followed by the formation of the MP-A network (T g = 10 °C) which was confirmed by FT-IR, SEM, DMA, and a separately prepared composite polymer consisting of MA-V particles embedded in an MP-A matrix. The triple shape memory effect was characterized using DMA, and it was demonstrated that the shapes could be programmed either by a one-step (single temperature) or a two-step method (two different temperatures). This material was able to hold its transitional shape for an extended time period (>1 h) at intermediate temperature (20 °C) between its two T g s, mainly due to narrow transitions of two separate networks. This new approach to obtain dual polymer networks with distinct transitions and characteristics is simple and robust, thus enabling applications in areas such as triple shape memory polymers, biomedical materials, and composites.

Dually Actuated Triple Shape Memory Polymers of Cross-Linked Polycyclooctene–Carbon Nanotube/Polyethylene Nanocomposites

“…In contrast, triple and multiple SMPs could provide more complex actuation because they have two and more temporary shapes besides a permanent shape. [44][45][46][47][48] Generally speaking, double SMPs need only a reversible phase, while triple and multiple SMPs need two and more reversible phases, respectively. An interesting strategy to get triple and even multiple SMEs was to use the broad glass transition of polymers.…”

Multiple shape memory polymers based on laminates formed from thiol-click chemistry based polymerizations

“…Analogous to the networks employed in our recent TSM composite example 24 , the same monomers were utilized here to fabricate the layers of a bilayer film.…”

“…Recently, we showed a TSMP incorporating two distinct thiol-Michael polymer network composites with varied glass transition temperatures 24 . The selective reaction between thiol and ene monomers has led us toward the synthesis of near-IPN type of material consisting of two thiol-Michael network domains within one sample and obtained in a one pot procedure.…”

Micromachined Shape-Memory-Alloy Microactuators and Their Application in Biomedical Devices

“…In TRSME, the material can recover from temporary shape to original shape through two intermediate predefined shapes. Unlike the SMPs that have much attention from researchers of the TRSME [81][82][83][84], the research progress of such effect in SMA is somehow stagnant. To the best knowledge of the authors, the only study of TRSME in SMA is reported by Tang et al [85].…”