(766e) Controlling Polymerization Induced Phase Separation (PIPS) Using the Nonlinear Optical Properties of Light

The organization of polymer blends and polymer solutions is critical for their processing into functional materials, which are attractive for applications in lithium-ion and proton transport; thermo-electrics; solid-state lighting; and advanced composites. Scalably and precisely controlling their morphology remains a challenge, yet is crucial for the advancement of their structure-property relationships. To this end, photopolymerization-induced phase separation (PIPS) is a promising route to morphology control, and uniform irradiation and holographic polymerization are currently the two major approaches. We report our recent work on controlling PIPS of both photoreactive polymer blends and photopolymer-solvent mixtures by eliciting nonlinear optical interactions between the mixtures and the irradiation source. Photopolymerization induces changes to the refractive index of the mixtures that result in strong modulations to light propagation, which creates spatially varying photopolymerization rates. Thereby, a variety of optical patterns spontaneously form, and PIPS is induced in the regions of high intensity. As a result, the mixtures evolve into a morphology that mimics the profile of the transmitted light. We harness this mutual, dynamic interaction between polymer and light to direct morphology evolution in photopolymers, binary polymer blends, and photopolymer-solvent mixtures. Precise control over morphology is achieved over large areas and depths. The new types of morphologies achieved are discussed in terms of their potential applications as solid polymer electrolytes, separation membranes, and anti-wetting surfaces. Coupling nonlinear optical dynamics to the nonlinear chemical dynamics of phase separation represents a fundamentally new processing approach to control phase evolution in polymer mixtures.