Effects of polymer concentration and zone drawing on the physical properties of poly(N-vinylcarbazole) thick film

Abstract

To check the possibility of zone-drawn poly(N-vinylcarbazole) (PVK) thick films as base materials of photorefractive polymers, the effects of the initial polymer concentration and zone drawing on the physical properties of PVK film were investigated. PVK films were prepared from 1,1,2,2-tetrachloroethane (TCE) solutions with different initial concentrations. To investigate the drawing behavior of the PVK films with different solution concentrations, the films were drawn under various zone-drawing conditions. Through a series of experiments, it turned out that the initial concentration of the PVK solution in TCE caused significant changes in the draw ratio of the PVK film, that is, the zone draw ratios of the film at an initial concentration of 9.8 g/dL exhibited their maximum values and gradually decreased at higher or lower concentrations. Thus, it was determined that the initial concentration of 9.8 g/dL is the optimum polymer concentration to produce the maximum draw ratio in this work. The lightness (whiteness) of the zone-drawn PVK film was much higher than that of the hot-drawn PVK film, resulting from diminishing microcrystallite formation, crystallization, and back-folding of molecular chains by zone drawing. Moreover, the mechanical properties of the PVK film were dominantly improved by introducing a zone-drawing technique, maintaining lightness of the zone-drawn film to a similar degree as that of the undrawn film. (C) 2001 John Wiley & Sons, Inc.