Simulation study of shape memory polymer networks formed by free radical polymerization

Chemically crosslinked thermoset shape memory polymers (TSMPs) can combine the strength required for load-carrying structures and devices with stimuli-responsive properties that can allow them to perform crack-closing or other multifunctional properties. In particular, UV-curable shape memory polymers can be used for 3D printing, and to enhance the design process, a molecular dynamics (MD) modeling framework was developed to study them. The MD simulations were used to calculate thermophysical, mechanical, and shape memory properties for glycerolate dimethacrylate after UV-curing to form a polymer network. Semiquantitative agreement between simulation and experiment was achieved for the different properties compared. By examining various conditions for network formation, a range of distinct cross-linking topologies were generated and their effects on properties were evaluated. In particular, it was found that the percentage of monomers with the maximum number of possible links with other monomers had a greater correlation with recovery stress than the number of monomers reacted overall. A new topological fingerprint, the average minimum pathway between monomers, was proposed and found to have the strongest correlation with recovery stress than all properties examined.