Composition Control of Aromatic Copolyesters by Shearing

Abstract

Composition control of copolyester was examined by using hydrodynamically induced phase separation, during solution polymerization, of p-acetoxybenzoic acid and m-acetoxybenzoic acid (m-ABA). Polymerizations were carried out in liquid paraffin at 1.0% of concentration under shear flow. The polymers were obtained as precipitates formed via phase separation of oligomers and the subsequent polymerization in the precipitates. When the feed ratio of m-ABA (χ f ) was 20 mol %, the molar ratio of m-oxybenzoyl moiety in the precipitated polymers (χ p ) was 5.3, 3.1, and 2.3 mol % at a shear rate (γ) of 0, 147, and 489 s -1 , respectively. The values of χ p were much lower than those of χ f , and shear flow lowered the value of χ p ; thus, controlling shear flow influenced both the reaction rate of the monomers and the miscibility of the oligomers. It especially enhanced the difference on the miscibility between homo-oligomers and co-oligomers. This change in the miscibility by shear flow brought about the more rapid precipitation of homo-oligomers than co-oligomers, leading to the selective formation of poly(p-oxybenzoyl).

Morphological diversity and nanofiber networks of poly(p‐oxybenzoyl) generated by phase separation during copolymerization

“…It has been reported previously that the stirring influenced the phase‐separation behavior of the oligomers and the apparent reaction rate of monomers, bringing about the change in the morphology and the composition of copolymers 31. The χ p value under stirring was 7.3 mol % and it was almost the same as that without stirring of 7.9 mol %.…”

“…In order to increase the N p av value and to decrease the diameter of the fiber, the stirring was applied to the polymerization of ABA with DABA at χ f of 15 mol % at a concentration of 1.5% in DBT at 320°C. It has been reported that the stirring accelerated the fibrillation of the POB whiskers to yield the fibrillated fine fibers 31. The precipitates were obtained under stirring at γ was 147 s −1 with the yield of 12%.…”

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

“…Wide‐angle X‐ray scattering (WAXS) was performed on a Rigaku Gaiger Flex with nickel‐filtered CuKα radiation (35 kV, 20 mA). Rate constants of the condensation reaction of AMBA and AABA were estimated kinetically by the measurements of eliminated acetic acid according to the previously reported procedure …”

“…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 .…”

“…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 . This previous study showed that the shearing affected both the reaction rate of monomers and the solubility of oligomers, leading to the enhancement of chemoselectivity.…”