Role of Miscibility in the Shape Memory Properties of Polymer Blends

Shape Memory Polymers(SMPs) are smart materials capable of transforming back to their intended shape and therefore, are used to replicate biomimetic functionalities in artificial materials. Here, we demonstrate that unlike chemical synthesis, polymer blending can be used as an effective technique to design SMPs. In our work, we consider partially miscible crystalline and amorphous polymer blends, to represent the hard and soft segments of SMPs, respectively. To determine the miscibility of blend we construct equilibrium phase diagram by combining Flory-Huggins and phase-field theories that account for both, amorphous-amorphous and crystal-amorphous interactions. We incorporate the effect of these interactions into standard viscoelastic model and determine thermo-mechanical behaviour of SMP blend, using composition dependent viscoelastic properties calculated from Equivalent Box Model. Finally, via simulations, we determine shape fixity and recovery ratios and demonstrate that our calculations are in excellent agreement with the experimental results for PCL-SBS blends. We believe that our findings can not only be utilized to design SMP blends with tailored properties but also be used to establish their structure-property relationships.