화학공학소재연구정보센터
Macromolecules, Vol.30, No.18, 5271-5278, 1997
Kinetic-Analysis of Polymerization Rate Acceleration During the Formation of Polymer/Smectic Liquid-Crystal Composites
Polymerization and segregation behavior of n-decyl acrylate in a smectic liquid crystal were characterized. The polymerization rate increased dramatically as the temperature was decreased and the order of the liquid crystalline media increased. To ascertain the kinetic mechanisms behind this behavior, the kinetic constants of both the termination and propagation reactions were determined. The overall rate increase was driven by an increase in the propagation kinetic constant despite an increase in the termination kinetic constant. The segregation behavior of the monomer in the liquid crystal was also elucidated using polarized infrared spectroscopy and X-ray diffraction. The monomer segregated between the smectic layers, thereby concentrating the monomer double bonds in a much smaller volume. Using this type of segregation with the consequent layer spacing increase and assuming that diffusional limitations are negligible, a kinetic model was developed to explain the increases in polymerization rate as well as the increases observed in the kinetic constants. After analysis of both steady-state and unsteady state conditions, increases in the polymerization rate and propagation and termination kinetic constants related to the increase in the layer spacing were predicted. These predictions agreed well with experimental results of polymerization rate and kinetic constants, indicating that this model is suitable in explaining the mechanisms driving the increases in both propagation and termination rates in this and other monomer/smectic liquid crystal systems.