Polymerization behavior and kinetics during the formation of polymer-stabilized ferroelectric liquid crystals

The effects of photopolymerizing both mesogenic and nonmesogenic diacrylate monomers in ferroelectric liquid crystalline media were characterized. By using monomers with a variety of different physical and optical properties, the influence of the monomer as well as the ordered media was determined. Polymerization rate profiles and double-bond conversions were monitored at different temperatures and in different liquid crystalline phases. As the order of the media increased, the polymerization rates also increased dramatically for all of the monomers studied, despite large decreases in temperature. Solution polymerizations in the liquid crystal at temperatures for which the liquid crystal molecules are isotropically distributed and in an isotropic solvent were much slower and exhibited maximum rates less than one third those observed in ordered phases. To elucidate the mechanisms behind this behavior, the kinetic constants of both the termination and propagation reactions were determined. For certain monomers, the rate increase was driven by a decrease in the termination kinetic constant causing an increase in the radical concentration. On the other hand, other monomer polymerizations in ordered phases exhibited an increase in both termination and propagation kinetic constants. The effects of increasing monomer concentration in the ferroelectric liquid crystal were also investigated.