Size control of poly(p-oxybenzoyl) whiskers by addition of crystals during polymerization of p-acetoxybenzoic acid

Control of the size, such as the length and width, of poly(p-oxybenzoyl) (POB) whiskers is a desirable technology. In this study, the addition of nuclei to the polymerization system is examined to control the size of the POB whisker. Polymerizations were carried out in liquid paraffin at 330°C for 6 hr. The polymerization concentration was 1%. The crystals were prepared for 10 min, of which the tip angle is 80°, are added as nuclei to the polymerization solution just before the crystallization is about to begin. The length does not increase at all by addition of the added crystals. The width increases and its distribution becomes significantly broader in all cases. The broadness of the width distribution reveals that nuclei are newly formed in the course of polymerization after the addition of crystals. It is difficult to inhibit the generation of new crystals by the control of the number of added crystals because the precipitation rate of the oligomers is much higher than the consumption rate of the oligomers by crystallization and therefore the excess oligomers which cannot participate in the crystal growth induce nucleation. It is concluded that the addition of the crystals as nuclei is not an available method to lengthen the POB whisker.