Coupling polymeric systems to nonlinear dynamics offers opportunities to create materials with tailored morphology and function 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 autoacceleration, 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 with three examples. First, in a family of photoinitiated polyfunctional acrylates, we demonstrate how crosslinking interacts with the optical instability, whereby it regulates both optical pattern formation and resultant microstructure. Secondly, in a blend of photoreactive monomers, we show how nonlinear waves induce and regulate microscale, spatially-local spinodal decomposition (chemical instability) along their path lengths, leading to a large-scale, multiphase morphology that corresponds to the arrangement of self-trapped beams. Thirdly, micro-porous materials are produced through nonlinear optical pattern formation in a photopolymer-solvent mixture, wherein the solvent behaves like a porogen and can be removed after the reaction. 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.

Coupling nonlinear optical dynamics to polymer systems for light-directed evolution of morphology

255th National Meeting (2018)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.