Polymer, Vol.156, 228-239, 2018
Tuning of reversible actuation via ROMP-based copolymerization semicrystalline polymers
There exists a need for reversible actuation involving two-way shape memory polymers that can respond to changes in ambient temperature in the 20 degrees C-40 degrees C range, especially for soft actuators in applications requiring near-room-temperature environmental responsiveness. Herein, we report on the fabrication and analysis of a family of soft, semicrystalline copolymers based upon cis-cyclooctene and various melting point reducing comonomers via ring-opening metathesis polymerization (ROMP). Reversible actuation behavior of such copolymers was tuned by varying not only the species and the incorporation level of a second comonomer but also the concentration of an incorporated thermal initiator for crosslinking. Results revealed that actuation was tuned to occur best and near room temperature for a copolymer consisted of 97 mol% cis-cyclooctene and 3 mol% 1,5-cyclooctadiene and 0.50 wt% dicumyl peroxide initiator. Also, all crosslinked copolymers feature actuation magnitude greater than 50% and recovery magnitude greater than 94% at a single stress of 0.8 MPa, while thermal strain hysteresis was 17.5 degrees C in breadth, on average.