Effects of Controlling Polymer Nanostructure Using Photopolymerization within Lyotropic Liquid Crystalline Templates

A promising method of synthesizing polymers with useful property relationships utilizes self-assembling lyotropic liquid crystals (LLCs) as photopolymerization templates to direct polymer structure on the nanometer scale. Unfortunately, thermodynamically driven phase separation of the polymer from the LLC template often occurs during polymerization and prevents control over final polymer nanostructure and properties. In this work, the nanostructure of polyacrylamide is controlled through photopolymerization in LLC templates formed using specific concentrations of polymerizable and nonreactive surfactants. Polymer structure information obtained using electron microscopy, X-ray scattering, and polarized light microscopy indicates that LLC nanostructure is retained during photopolymerization at particular reactive surfactant concentrations. Physical properties including water uptake, diffusivity, and mechanical strength are greater in polyacrylamide systems that exhibit nanostructure as compared to isotropic controls of the same chemical composition. Useful property relationships typically unattainable in traditional hydrogel systems are also observed for nanostructured hydrogels including simultaneous increases in water uptake and mechanical strength. These results demonstrate methods of generating and retaining polymer nanostructure during photopolymerization in systems that otherwise phase separate from the LLC template and may be utilized to synthesize nanostructured polymers with property relationships useful in a growing number of advanced applications.