Photoinduced Phase Transition in Microstructured Ionic End-functionalized Polymer Blends

Compatibilization of immiscible polymer blends is critical to increasing the fraction of industrial plastics that are recycled. We demonstrate that the simple functionalization of the chain ends of incompatible polymers with oppositely charged groups leads to electrostatically stabilized microdomains and suppressed macroscopic phase separation. A functionalized polydimethylsiloxane with a photochromic diarylethene end-group (PDMS-ω-DAE) is blended with a sulfonic acid end-functionalized polystyrene (PS-ω-SO₃H). The proton transfer between the acid and base units in the melt state yields contact ion pairs that self-assemble into a cylindrical microstructure. Further, due to the light sensitivity of the DAE, irradiation of the blend triggers isomerization from the ring-opened (DAE-O) to the ring-closed (DAE-C) form. The more localized positive charge on DAE-C leads to stronger ionic bonds and induces a phase transition to a lamellar microstructure.