Templating Polymer/Chromophore Co-Crystallization in Block Copolymer Domains

Future advances in optical information processing are dependent on new materials that can manipulate light, similar to electronic materials that control electrons. Although advances in design parameters have led to significant progress in organic nonlinear optical (NLO) materials, long-term stability and material processing have prevented widespread implementation. Recently we reported an alternative approach in which an NLO chromophore is co-crystallized with a polymer, forming a non-centrosymmetric hybrid host-guest complex. Although the materials demonstrate promise, the orientation of co-crystals in the films randomize at elevated temperature, resulting in a loss of second harmonic generation (SHG) activity that is not reversible on cooling. To improve the thermal stability and harness reversible SHG activity, polymer/chromophore films were prepared using a poly(styrene)-poly(ethylene oxide) (PS-PEO) diblock copolymer as the template to confine the PEO/chromophore co-crystals between rigid PS domains. Interestingly, the  PS-PEO/chromophore samples self-assemble into a gyroid morphology, which has the potential to exhibit chiral SHG. The work presented here opens new avenues for creating materials exhibiting responsive and chiral-dependent SHG properties.