Selective preparation of poly(p‐oxybenzoyl) by using fractional polycondensation

Abstract

Selective preparation of poly(p‐oxybenzoyl) (POB) in the copolymerization system of p‐acetoxybenzoic acid (p‐ABA) and m‐acetoxybenzoic acid (m‐ABA) was examined by using reaction‐induced crystallization of oligomers. Polymer crystals mainly composed of p‐oxybenzoyl moiety were precipitated when the content of m‐ABA in the feed was 30 mol %. The formation of the polymer crystals was attributed to both the reactivity of monomer and the phase‐separation behavior of oligomer. Reactivity of p‐ABA was twice higher than that of m‐ABA, and thereby, the homo‐oligomers of p‐oxybenzoyl moiety were more rapidly formed in solution than do co‐oligomers at the early stage in polymerization. They were selectively precipitated by crystallization to form crystals because of low miscibility. Co‐oligomers containing m‐oxybenzoyl moiety were also formed in solution, but they were unable to be phase‐separated because of higher miscibility. Further polycondensation occurred between oligomers in the precipitated crystals, leading to the formation of POB. This polymerization proceeded with selecting certain monomers by crystallization and afforded a new methodology for fractional polycondensation. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2732–2743, 2006

Heterogeneous polycondensation for composition control of poly(p -mercaptobenzoyl-co-p -benzamide) by shearing

“…Although the yield of the precipitates at χ f of 70 mol % under shearing was only 6.8%, the precipitates were obtained under shearing with the yield of 16.3–47.0% at other χ f values. It has been reported that the yield of the precipitates generally decreases in the middle range of the χ f vales owing to the higher solubility of co‐oligomers . Correspondingly, the yields in these polymerizations became lower at χ f of 50–70 mol % whether the shearing was applied or not.…”

“…On the other hand, the heterogeneous polycondensation which is the polymerization performed in multiple phases such as a solution phase and a solid phase has been developed for the precise control of not only the primary polymer structures but also their higher‐ordered structures. The heterogeneous polycondensation containing the reaction‐induced phase separation had provided sequence control of whiskers, dual self‐assemble polycondensation, and fractional polycondensation . Among them, the fractional polycondensation which is the polymerization to synthesize homopolymers chemoselectively as precipitates in the copolymerization system has a potential to control the composition of copolymers, and the composition control of aromatic copolyesters had been studied by using hydrodynamically induced phase separation during solution polymerization of p ‐acetoxybenzoic acid and m ‐acetoxybenzoic acid .…”

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

“…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.…”

“…Fractional polycondensation, which is one of the precise polycondensations, was reported as the polymerization proceeding by selecting certain monomers in the copolymerization system. Copolymers rich in p ‐oxybenzoyl ( p ‐OB) moiety were selectively synthesized as precipitates from the copolymerization of p ‐acetoxybenzoic acid ( p ‐ABA) and m ‐acetoxybenzoic acid ( m ‐ABA) by using the reaction‐induced crystallization of oligomers during polymerization without shearing 6. The selectivity in this heterogeneous polymerization is brought by not only the difference in the reactivity of monomers but also that in the precipitation behavior of the oligomers depending on their composition.…”