Title

Polymerization Kinetics and Morphology of Side Chain Liquid Crystalline Monomers and UV Curing of Multifunctional Acrylates

Date of Award

1995

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Polymers and High Performance Materials

First Advisor

Charles E. Hoyle

Advisor Department

Polymers and High Performance Materials

Abstract

Polymerization kinetics of several liquid crystalline monomers has been studied using both medium pressure mercury lamp and excimer laser (XeF, 351 nm) and photoinitiator to initiate the photopolymerization in different mesophases as well as in the isotropic phase. Monomers used were characterized by a combination of optical microscopy, DSC. The morphology of the semifluorinated liquid crystalline monomers and corresponding polymers were also examined by X-ray diffraction spectroscopy. The general kinetic behavior of the monomer was elucidated due to different kinetics of continuous (mercury lamp) and pulsed (excimer laser) light sources. In-situ light scattering was used to determine the transient phase behavior of the monomers studied. Kinetic rate constants were evaluated by steady-state analysis and decay of polymerization exotherm for one of the semifluorinated monomers. Phase diagrams for the monomer were also constructed to determine the kinetic equilibrium behavior of the monomer. Chain transfer to tertiary amine for several different liquid crystalline monomers was also evaluated. It is found that in more ordered phase the termination rate constant is usually much lower than less ordered phases. The rate of polymerization and the molecular weight distribution of the polymer generated, however, depend on the phase change during polymerization and the effect of phase on both propagation and termination rate constants. The smectic interlayer spacing is found to affect the primary termination in pulsed laser experiments. The liquid crystalline texture of the difunctional liquid crystalline monomer was found to be retained after polymerization until heated to elevated temperatures.