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

Abstract

Selective 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 of p‐acetoxybenzoic acid (p‐ABA), m‐acetoxybenzoic acid (m‐ABA), and their dimers. The crystals obtained from the copolymerization of the dimer of p‐ABA (p‐ABAD) and m‐ABA contained only 3.1 mol % of m‐oxybenzoyl moiety even at high content of m‐oxybenzoyl moiety in feed (χf) of 40 mol %. p‐Oxybenzoyl homo‐oligomers were more rapidly formed from p‐ABAD in the solution than from p‐ABA, and they were crystallized to form the crystals with segregating co‐oligomers. While co‐oligomers containing more m‐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 χf of 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

Selective synthesis of poly(p‐oxybenzoyl) by fractional polycondensation: Enhancement of selectivity by shearing

“…4). Although the selective synthesis was observed under shearing, the selectivity was almost the same as that in the polymerization without shearing,7 and the shearing at γ of 147 s −1 did not enhance the selectivity significantly. When the polymerizations were carried out at γ of 489 s −1 , the selectivity increased drastically.…”

“…The mechanism of the fractional polycondensation has been revealed on the basis of this phase diagram as follows6–8; p ‐OB homo‐oligomers are more rapidly formed in the solution than co‐oligomers due to the difference in the reactivity of monomers. When the molecular weight of the p ‐OB homo‐oligomers exceeds a critical value, they are precipitated via crystallization to form crystals at the early stage in the polymerization.…”

“…Precise control of polycondensation is of great importance to create new polymer materials from the academic and industrial aspects. Many attractive polycondensation methods have been developed so far, including synthesis of sequence‐defined polymers,1 condensative chain polymerization,2 solid‐state polycondensation,3 nucleation‐elongation polymerization,4 nonstoichiometric polycondensation,5 and fractional polycondensation 6–8. Fractional polycondensation, which is one of the precise polycondensations, was reported as the polymerization proceeding by selecting certain monomers in the copolymerization system.…”

“…The oligomers rich in p ‐OB moiety are precipitated more rapidly to form the crystals than those rich in m ‐oxybenzoyl ( m ‐OB) moiety. The polymerization of 4‐(4‐acetoxybenzoyloxy)benzoic acid ( p ‐ABAD), which was the dimmer of p ‐ABA, with m ‐ABA was also examined and it became clear that the dimmer effect made the selectivity higher 7. Further, the composition control of copolymers in the polymerization of p ‐ABA and m ‐ABA had been previously studied using hydrodynamically induced phase separation during solution polymerization 8.…”