Investigation of polymer nanostructure evolution during the formation of polymer/smectic liquid crystal composites

Polymer stabilized liquid crystalline systems (PSLCs) have been of considerable research interest due to their great potential in liquid crystal display applications. Of particular importance in the properties of PSLC systems is the evolution of the polymer nanostructure. The unique characteristics of fluorinated monomers not only may provide unique polymer nanostructure but also may enhance desirable properties of PSLC materials. This study focuses on the polymerization and polymer nanostructure of low surface energy fluorinated materials in a liquid crystalline solvent. Enhanced polymerization rates are observed as the order of the liquid crystalline solvent is increased with particularly pronounced acceleration for a fluorinated monoacrylate. This behavior is primarily due to segregation both before and after polymerization. Fluorinated monomers segregate between the smectic layers of the liquid crystal comparable to segregation behavior of analogous aliphatic monomers. The monomer structure has a significant impact on the polymer segregation behavior in these polymer/liquid crystalline composites as well. Network polymer structures, obtained from both aliphatic and fluorinated diacrylate monomers, phase separate from the liquid crystal while linear fluorinated polymer structures remain segregated between the smectic layers of the liquid crystal. Not only does this linear polymer remain between the smectic layers and retain its segregation behavior throughout the polymerization, but the polymer is also ordered to a much greater degree than the monomer. This ordered structure significantly alters the polymer/LC interaction and leads to birefringence at temperatures well above the liquid crystalline isotropic clearing point.