Self-assembly and luminescence of oligo(p-phenylene vinylene) amphiphiles

We have synthesized a series of amphiphilic molecules consisting of oligo(phenylene vinylene) (OPV) asymmetrically end-substituted with a hydrophilic poly(ethylene glycol) (PEG) segment and a hydrophobic alkyl chain. This amphiphilic structure induces self-assembly into both thermotropic and lyotropic lamellar liquid crystalline (LC) phases. The molecules form strongly fluorescent, self-supporting gels in both water and polar organic solvents, even at high concentrations on the order of 30 wt%. These self-assembled structures have been characterized by small-angle X-ray scattering (SAXS), differential scanning calorimetry (DSC), and polarized optical microscopy (POM). Photoluminescence (PL) is influenced by the structure of the material, with enhanced emission in the LC state due to assembly of the chromophore in confined two-dimensional layers. Self-assembly controlling molecular aggregation at the nanoscale could significantly improve the performance of OPV-based materials in optoelectronic devices.