Abstract
The unique properties of liquid crystals (L.C.) continue to find application in an ever-increasing number of diverse fields, such as liquid crystal electro-optic display devices, in analytical chemistry as substrates for gas chromatography, and as L.C. based commercial fibers of high tensile strength, in particular nematic isotropic solution of poly (p-bezamide). Liquid crystals in general allow the nondestructive thermal analysis of everything from aircraft structures to electronic components and so on. Chapter I investigates the mechanical, optical and thermal behavior of basically two types of elastomers, namely, polyphosphazene and poly(dimethylsiloxane) PDMS. The aim was to look for the effect of diluents on the above mentioned elastomers when their isotropy phase is perturbed via strain, and what this anisotropy, or orientation contributes to both optical and mechanical properties. These studies were made, and are represented by the results obtained from the mechanical and optical behavior of these elastomers after they are swollen with these diluents. Chapter II and III deal with the experimental investigation of the mechanical properties of poly(ethylacrylate) networks reinforced with silica (SiO$\sb2$) during emulsion polymerization, and poly(dimethylsiloxane) reinforced with zeolite fillers, respectively. Chapter IV covers experimental studies which were performed to determine the effect that cross-linking a network in solution has on its strain-induced crystallization. A series of networks were cross-linked in the presence of different amounts of solvent to try to diminish the number density of entanglements, and hence to affect the strain-induced crystallization. The results were represented again by the mechanical properties and the volume fraction of the polymers with respect to the value of elongation at which the polymer tends to deviate from rubberlike elasticity theory as a result of the crystallites formed when these polymers are stretched. These crystallites act as physical cross-links and hence, at a certain stage of elongation, contribute to the modulus of the polymers. This is an internal reinforcement that many other polymers do not exhibit. The results did not show significant effect of the presence of the solvent over this phenomena. (Abstract shortened with permission of author.)