Poly(p‐oxybenzoyl) (POB) crystals were prepared with the reaction‐induced crystallization of oligomers during the direct polycondensation of p‐hydroxybenzoic acid (HBA) with p‐toluenesulfonyl chloride (TsCl) and N,N‐dimethylformamide in pyridine. Sheaflike lozenge‐shaped POB crystals were obtained, of which the longer diagonal was 7.0–8.0 μm. The influence of the polymerization condition on the morphology was examined to optimize the preparative condition for the crystals exhibiting the clearest habit, and the favorable condition was determined as the molar ratio of TsCl to HBA of 1.3 and polymerization concentration of 3.0%. The crystals possessed extremely high crystallinity and outstanding thermal stability. The formation mechanism of the crystal was proposed as follows. When the number‐average degree of polymerization of the oligomers exceeded a critical value of about 4, they were precipitated to form the hexagonal lamellae. The crystals were grown very quickly to lozenge‐shaped crystal through screw dislocation with the continuous precipitation of oligomers from the solution. Finally, the further polymerization occurred in the precipitated crystal with developing polymer‐chain packing. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3275–3282, 2003

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Morphology control of poly(2‐oxy‐6‐naphthoyl) (PON) was examined by using reaction‐induced crystallization of oligomers during direct polycondensation of 2‐hydroxy‐6‐naphthoic acid with p‐toluenesulfonyl chloride and N,N‐dimethylformamide in pyridine. PON particles were obtained of which the diameter was in the range of 8.0–8.3 µm. The particles were comprised of many lamellae and exhibited spherulitic morphology. They possessed high crystallinity evaluated from wide‐angle X‐ray scattering (WAXS). Formation mechanism of the particles was clarified from the results of morphology observation, yield, density and WAXS. When the number average degree of polymerization of the oligomers exceeded a critical value of ca. 4–5, they were precipitated to form lamellae. The lamellae grew to spherulites through screw dislocation with continuous precipitation of the oligomer from the solution. Finally, further polymerization occurred gradually in the precipitates. Copyright © 2005 John Wiley & Sons, Ltd.

We have studied the morphology of poly( p-oxybenzoyl) (POB) crystals prepared by the direct polycondensation of p-hydroxybenzoic acid (HBA) using diphenyl chlorophosphate (DPCP) in the presence of N,N-dimethylformamide. Lozenge-shaped sheaf-like POB crystals were obtained of which the longer diagonal was 16.0-16.5 μm. Favorable polymerization conditions to prepare the crystal exhibiting clear crystal characteristic were the molar ratio of DPCP to HBA of 1.5, the molar ratio of DMF to HBA of 2.6 and the polymerization concentration of 3.0%. The crystals were comprised of low molecular weight polymer of which the degree of polymerization (DPn) was 14 and possessed extremely high crystallinity. The formation mechanism of the crystals was considered by the polymerization time dependences of morphology, yield, density, DPn, crystallite size, and lattice constant as follows. When the DPn of the oligomers exceeded a critical value of about 3, they were precipitated to form the hexagonal lamellae. The lamellae grew very quickly to sheaf-like lozenge-shaped crystal through the screw dislocation with the continuous precipitation of the oligomer from the solution. Finally, further polymerization and the reorganization of polymer chains occurred in the precipitated crystals.