Dispersity and architecture driven self-assembly and confined crystallization of symmetric branched block copolymers

The effect of macromolecular architecture on the morphology and thermal characteristics of triblock copolymers was evaluated for linear, H-shaped, and arachnearm architectures with poly(cis-cyclooctene) (PCOE) midblocks flanked with arms of poly(d,l-lactide) (PLA). Chain topology was found to significantly influence the interfacial curvature of the microphase separated domains, as implicated by morphological differences observed by transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS). The branched molecular architectures and molar mass dispersities (D) of the triblock polymers examined here resulted in a significant shift in the phase boundaries between conventional equilibrium microphase separated structures to higher volume fractions of the end blocks (i.e., PLA) as compared to conventional low dispersity linear triblocks. Macromolecular topology was also found to strongly influence the extent of homo- vs. heterogeneous nucleation in the semi-crystalline PCOE block. The culmination of the bulk phase behavior analysis demonstrates the ability to fine-tune the properties of the block polymers by exploiting different architectures through a synthetically straightforward route.