Acid and base treatment of glass and mica substrates affects the phase II/I crystal structure ratio of poly(p-oxybenzoic acid) polymerized by the confined thin film melt polymerization (CTFMP) technique; acid treatment of mica enhances the phase I content, whereas base treatment of glass and mica results in growth of 100% phase II crystals. In bulk melt polymerized samples, without added catalyst, the fraction of phase II increases with increasing polymerization temperature, up to 25-30% above 300 degrees C; this is suggested to be related to a "PH phase" (pseudo-hexagonal), consisting of 3 pairs of phase I and II crystals, rotated by 60 degrees, in CTFMP samples annealed above their Tk-m. The addition of a base to the polymerization system also results in an increase in the phase II content, up to almost 100% in some cases. The effect of the addition of base is tentatively attributed to a change in the alignment of neighboring molecules growing out from the initial nucleus during the simultaneous polymerization (liquid crystal) crystallization.