Effect of miscibility on shape memory characteristics of Polymer Blends

Designing programmable shape shifting materials has been a grand challenge for science and engineering. Shape Memory Polymers (SMPs) are smart materials that have the ability to transform back to their intended shape when the external conditions are reversed. One of the strategies for synthesizing SMPs is to bond soft and rigid chemical moieties with one another through polymerization. Although polymer blending offers a simple strategy, it has not been used as a preferred technique to design SMPs. As most of the polymer blends are immiscible, synthesizing SMPs through blending route introduces a new set of challenges. Here, we use the equilibrium phase diagram to examine the role of compatibility of the constituent polymers on the characteristics of SMP blend. Specifically, we use Flory-Huggins theory in conjunction with the phase-field theory to capture the amorphous-amorphous and crystal-amorphous interactions in the SMP blends, respectively. Subsequently, we use the thermo-mechanical constitutive model to demonstrate the effect of miscibility on shape fixity and shape recovery of the SMP blend. Our approach can be utilized to design SMP blends with tunable properties and allows a mechanism to establish structure-property relationships in these systems.