Monday, November 5, 2007 - 8:30 AM
32a

Photopolymerization In Nanostructured Systems

C. Allan Guymon, Chemical and Biochemical Engineering, University of Iowa, Department of Chemical and Biochemical Engineering, Iowa City, IA 52242

The ability to control nanostructure in materials has recently generated significant excitement over the past few years. While development of inorganic materials with specific structures on the nanometer size scale has been repeatedly demonstrated, similar structures in organic materials have been much more elusive. Promising routes to such materials will be discussed that utilize a combination of photopolymerization and liquid crystals to allow templating for nanostructured organic and inorganic polymers. The dynamics that govern control of the polymeric structure are strongly dependent on both liquid crystalline phase and photopolymerization behaviour. This work will focus on using lyotropic liquid crystals (LLCs), or high concentration surfactant/water mixtures, and photopolymerization to template the polymer structure. The photopolymerization behavior plays a critical role in understanding and controlling the ultimate polymer morphology. Typically, the fastest polymerization rates are observed in the more ordered phases. In fact, in certain systems, polymerization rate is ten times faster in the ordered phases when compared to an isotropic polymerization. These large increases in polymerization rate are induced by segregation and increased ordering effects that limit diffusion of growing polymer chains. Additionally, the polymerization rate substantially alters the ultimate polymer structure and physical. Using photopolymerization allows formation of periodic structures on the nanometer size scale while slower polymerization techniques such as thermal polymerization induce gross phase separation with little indication that a nanostructured template was used.