Dimer effect on fractional polycondensation of poly(p‐oxybenzoyl)

Abstract

AbstractSelective preparation of poly(p‐oxybenzoyl) (POB) crystals was examined from the viewpoint of a dimer effect on fractional polycondensation. Four different copolymerization systems were chosen as the combinations ofp‐acetoxybenzoic acid (p‐ABA),m‐acetoxybenzoic acid (m‐ABA), and their dimers. The crystals obtained from the copolymerization of the dimer ofp‐ABA (p‐ABAD) andm‐ABA contained only 3.1 mol % ofm‐oxybenzoyl moiety even at high content ofm‐oxybenzoyl moiety in feed (χf) of 40 mol %.p‐Oxybenzoyl homo‐oligomers were more rapidly formed fromp‐ABAD in the solution than fromp‐ABA, and they were crystallized to form the crystals with segregating co‐oligomers. While co‐oligomers containing morem‐oxybenzoyl moiety were formed in the solution, afterward they were unable to be phase‐separated because of higher miscibility. The further polycondensation proceeded in the precipitated crystal, and finally the POB crystal was selectively formed. Lower polymerization temperature and concentration enhanced the fractionability, and the POB crystals containing less than 1 mol %m‐oxybenzoyl moiety were prepared at χfof 30 mol %, 270 °C, and a concentration of 0.5%. The dimer effect on the fractional polycondensation was clearly observed. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1598–1606, 2008