MSE Seminar: Ian Hosein, Syracuse University
Coupling Nonlinear Optical Dynamics to Polymer Systems for Light-Directed Organization of Functional Materials
Coupling polymeric systems to nonlinear dynamics offers opportunities to create materials with tailored morphology and functionality via pattern forming processes. Examples include periodic striations from traveling fronts in thermal polymerization, coalescence of polymer films during dewetting, oscillatory gels, and phase separation. Here, we present a fundamentally new mechanism to organize polymeric materials that couples photopolymerization to the nonlinear dynamics of optical fields. In a new process of optical auto-acceleration, a positive feedback mechanism emerges between photopolymerization and transmitted light intensity, whereby a mutual, dynamic interaction emerges between optical field distribution and the underlying morphology of the polymer medium. The input light undergoes Modulation Instability – dividing into a multitude of microscale “self-trapped” beams, which are nonlinear waveforms characterized by divergence-free propagation through polymer medium. As a result, these nonlinear waveforms inscribe permanent microstructure consisting of microscopic “channels” in the polymer. This coupling between optical nonlinearity and morphology evolution will be demonstrated in polyfunctional acrylate systems, polymer blends, as well as polymer-solvent mixtures. As a demonstration of the potential of this new process and the material properties, their application as encapsulants for solar cells as well as for anti-wetting coatings will be discussed. Harnessing nonlinear optical pattern formation to direct the organization of polymeric materials opens opportunities for studying the fascinating complexity of nonlinear systems, while creating advanced microstructures that can serve functional roles in a host of applications.