Polyarylate Block Copolymer Research Articles

Fabrication of Hollow Fiber Membrane from Polyarylate–Polyarylate Block Copolymer for Air Separation

A process has been developed for spinning asymmetric hollow fiber membranes from a polyarylate–polyarylate block copolymer having a separation factor for pure gases in the oxygen–nitrogen pair of α(O2/N2) = 6.3 and an oxygen permeance coefficient of 2.4 Barrer. The effect of the polymer molecular weight, the composition of the dope solution, and the spinning parameters on the gas transport properties of the hollow fiber membrane and its geometry has been studied. The use of a polymer with a molecular weight of 67 kDa, as well as the introduction of surfactants into the dope solution, has made it possible to prepare samples of defect-free membranes with an oxygen permeance of 120 L(STP)/(m2 h bar) and a separation factor of α(O2/N2) = 6.5, which correspond to the selective layer thickness of 60 nm.

Photostabilizing of bisphenol A polycarbonate by using UV-absorbers and self protective block copolymers based on resorcinol polyarylate blocks

Bisphenol A polycarbonate degrades due to sunlight, humidity and oxygen. In this study two possible techniques to stabilize the polymer were compared, i.e. blending of UV-absorbers (UVAs) into the polymer or using block copolymers based on resorcinol polyarylates. Combination of different analysis techniques shows that the protection by UVAs is not as good as by the resorcinol polyarylate block copolymers. The block copolymer rearranges itself through a photo-Fries rearrangement within hours into a UV-absorbing top layer. Two different block compositions were studied, and the copolymer with the highest concentration of resorcinol polyarylate groups shows the best protection.

Application of styrene‐acrylonitrile random copolymer–polyarylate block copolymer as reactive compatibilizer for polyamide and acrylonitrile‐butadiene‐styrene blends

AbstractStyrene‐acrylonitrile random copolymer (SAN) and polyarylate (PAr) block copolymer were applied as a reactive compatibilizer for polyamide‐6 (PA‐6)/acrylonitrile‐butadiene‐styrene (ABS) copolymer blends. The SAN–PAr block copolymer was found to be effective for compatibilization of PA‐6/ABS blends. With the addition of 3.0–5.0 wt % SAN–PAr block copolymer, the ABS‐rich phase could be reduced to a smaller size than 1.0 μm in the 70/30 and 50/50 PA‐6/ABS blends, although it was several microns in the uncompatibilized blends. As a result, for the blends compatibilized with 3–5 wt % block copolymer the impact energy absorption reached the super toughness region in the 70/30 and 50/50 PA‐6/ABS compositions. The compatibilization mechanism of PA‐6/ABS by the SAN–PAr block copolymer was investigated by tetrahydrofuran extraction of the SAN–PAr block copolymer/PA‐6 blends and the model reactions between the block copolymer and low molecular weight compounds. The results of these experiments indicated that the SAN–PAr block copolymer reacted with the PA‐6 during the melt mixing process via an in situ transreaction between the ester units in the PAr chain and the terminal amine in the PA‐6. As a result, SAN–PAr/PA‐6 block copolymers were generated during the melt mixing process. The SAN–PAr block copolymer was supposed to compatibilize the PA‐6 and ABS blend by anchoring the PAr/PA‐6 and SAN chains to the PA‐6 and ABS phases, respectively. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2300–2313, 2002

Phase morphologies and mechanical properties of high‐impact polystyrene (HIPS) and polycarbonate blends compatibilized with polystyrene and polyarylate block copolymer

AbstractPhasemorphology and mechanical properties of blends of high‐impact polystyrene (HIPS) and polycarbonate (PC) blends compatibilized with a polystyrene (PS) and polyarylate (PAr) (PS–PAr) block copolymer were investigated. Over a broad range of composition from 50/50 through 30/70, HIPS/PC blends formed cocontinuous structures induced by the flow during the extrusion or injection‐molding processes. These cocontinuous phases had heterogeneity between the parallel and perpendicular directions to the flow. The micromorphology in the parallel direction to the flow consisted of stringlike phases, which were highly elongated along the flow. Their longitudinal size was long enough to be longer than 180 μm, while their lateral size was shorter than 5 μm, whereas that in the perpendicular direction to the flow showed a cocontinuous phase with regular spacing due to interconnection or blanching among the stringlike phases. The PS–PAr block copolymer was found to successfully compatibilize the HIPS/PC blends. The lateral size of the stringlike phases could be controlled both by the amount of the PS–PAr block copolymer added and by the shear rate during the extrusion or injection‐molding process without changing their longitudinal size. The HIPS/PC blend compatibilized with 3 wt % of the PS–PAr block copolymer under an average shear rate of 675 s−1 showed a stringlike phase whose lateral size was reduced almost equal to the rubber particle size in HIPS. The tensile modulus and yield stress of the HIPS/PC blends could be explained by the addition rule of each component, while the elongation at break was almost equal to that of PC. These mechanical properties of the HIPS/PC blends can be explained by a parallel connection model independent of the HIPS and PC phases. On the other hand, the toughness factor of the HIPS/PC blends strongly depended on the lateral size of the stringlike phases and the rubber particle size in the HIPS. It was found that the size of the string phases and the rubber particle should be smaller than 1.0 μm to attain a reasonable energy absorbency by blending HIPS and PC. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2347–2360, 2001

A chain geometry prediction of polystyrene and polyarylate block copolymer by a kinetic simulation model

The chain geometry of polystyrene (PS) and polyarylate (PAr) block copol- ymer was predicted by the simulation of the kinetics of the block-copolymerization route. The simulation model consisted of a combination of two models. In the first model, the kinetics of the free-radical polymerization of carboxyl-terminated telechelic PS (COOH-PS-COOH) was simulated for the determination of the molecular weight distribution. In the second model, the kinetics of the PS and PAr block copolymerization with COOH-PS-COOH was simulated by a Monte Carlo computation, with each react- ing functional group assigned by an integer. The number-average and weight-average molecular weights and the composition of the PS-PAr block copolymer, as calculated by the simulation models, were in good agreement with the experimental data. From this agreement, plausible predictions for the chain geometry (i.e., the type of block copoly- mer and length of each segment) were obtained that were practically impossible to analyze experimentally. The simulation results showed that more than 80 wt % of the block copolymer synthesized by this method was a composite of various types of multiblock copolymers and that the length of the PAr segment was almost the same as that of the homo-PAr obtained as a by-product. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 299 -309, 2000

Optical properties of polystyrene and polyarylate block copolymer and their control by morphology generation

Relationship between phase morphology and optical properties of polystyrene and polyarylate (PS-PAr) block copolymers synthesized from telechelic polystyrene has been investigated. In the PS-PAr block copolymers, the PAr domains with higher melt viscosity were dispersed in the PS phase matrix with lower melt viscosity over the wide range of their composition from PS/PAr = 25/75 to 75/25 (wt ratio). The PAr domain size was dependent on the reactive ratio of PAr determined analogously by the mole fraction of the fed telechelic polystyrene. By controlling the mole fraction of the telechelic polystyrene more than 0.016 in synthesizing the PS-PAr block copolymer, the size of PAr domains could be reduced to the microscopic scale (smaller than 100 nm). Then, the PS-PAr block copolymers exhibited almost the same transparency as PAr in spite of the large difference in the refractive index between the PS and the PAr phase. Birefringence free condition for the PS-PAr block copolymers was determined by not only the PS/PAr composition but also the balance in the degree of molecular orientation of these chains. The latter factor suggests that PS and PAr chains undergo inhomogeneous stress and relaxation history during the injection process. By controlling Mn (number average molecular weight) and weight fraction of the fed OH-PS-OH around 20 000 and 55 wt %, respectively, in the synthesis of the PS-PAr block copolymer, the PS-PAr block copolymer exhibited almost zero birefringence without any sacrifice of transparency. Because in the PS-PAr block copolymer low birefringence and high transparency can coexist by controlling the adequate feeding condition in the synthesis process, the PS-PAr block copolymer would be a promising material for optical applications, such as a substrate of optical disks or optical lenses. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 953–961, 2000

Synthesis of styrene–acrylonitrile random copolymers (SAN) and polyarylate block copolymers and the control of their mechanical properties by morphology generation

Synthesis of styrene–acrylonitrile random copolymers (SAN) and polyarylate block copolymers and the control of their mechanical properties by morphology generation

Synthesis of styrene-acrylonitrile random copolymers (SAN) and polyarylate block copolymers and the control of their mechanical properties by morphology generation

The idea of repulsion in random copolymers was applied to the miscibility modification between polystyrene (PS) and polyarylate (PAr) segments of PS–PAr block copolymer (PAr–PS–PAr). Acrylonitrile (AN), which has a large positive interaction parameter against styrene, was used as a miscibility modifier toward PAr segments. AN was introduced into the carboxyl terminated telechelic-PS at AN wt % ranging from 12 to 37 wt %. Based on these telechelic acrylonitrile–styrene random copolymers (SANx's where x represents AN wt %), SANx and PAr block copolymers (PAr–SANx–PAr's) were synthesized. The miscibility of SANx and PAr segments was estimated from the results of DSC with Fox's equation and spin–spin relaxation time measured by pulsed NMR. These results evidenced that the miscibility between PS and PAr segments can be modified by introducing AN into PS segments. The estimated volume fraction of the interfacial layer between SANx and PAr segments was increased as x was increased toward 24 wt %, around which the predicted miscibility reaches a maximum. Above that AN wt %, it began to decrease. The flexural strength increased as the miscibility between SANx and PAr segments increased. In particular, when x was between 20 and 30 wt %, PAr–SANx–PAr exhibited three times larger flexural strength than PAr–PS–PAr. The fracture behavior changed from brittle to ductile, even though the telechelic SANx by themselves exhibited almost the same fracture strength as the telechelic PS. The results of dynamic mechanical measurements and the percolation model suggested that around these AN wt % the continuum matrices in PAr–SANx–PAr changed from SANx phase to a cocontinuous phase of SANx and PAr. From these results, PAr–SANx–PAr was explained to perform such a high flexural strength by this phase change in the continuum matrices. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 127–137, 2000

A novel process for synthesizing polystyrene and polyarylate block copolymers utilizing telechelic polystyrene

A novel process for synthesizing polystyrene (PS) and polyarylate (PAr) block copolymers utilizing telechelic polystyrene was proposed. This process was comprised of three steps. In the first step, carboxyl-terminated telechelic polystyrene (COOH-PS-COOH) was prepared by free radical polymerization with 4,4'-azo-bis(cyanovalelic acid) (ACVA). In the second step, COOH-PS-COOH was reacted with bisphenol-A by the use of triphenylphosphine, hexachloroethane, and triethylamine to convert carboxyl groups into phenol groups (OH-PS-OH). In the third step, to produce the PS-PAr block copolymer, OH-PS-OH was added to a polyarylate synthesizing system where bisphenol-A and the mixture of tere/isophthaloyl dichloride (1: 1 mole ratio) were polymerized by solution polycondensation. PS-PAr block copolymers were successively obtained with relatively high PS copolymerization ratio. The ratio was over 70%, while there was a wide variety in molecular composition and molecular weight. Furthermore, by this process PS-PAr block copolymers can be obtained from step 1 through step 3 consecutively without isolating the intermediates. This method has potential for industrial applications.

The preparation and properties of polyarylate block copolymers by interfacial polycondensation

AbstractBlock copolymers of bisphenol A isophthalate and sebacate were prepared by a two‐step interfacial polycondensation. The copolymers had sebacate contents of 1 : 5 and 1 : 3 molar with block lengths (DP) of 4,9, and 19. Thermal analysis of the copolymers by DSC showed the Tm of PBI. The crystallizability of PBI chain segments in the block copolymers was confirmed by X‐ray diffraction. The Tm of the copolymers was primarily influenced by the DP of the chain segments rather than the sebacate content. The Tg of the copolymers was mainly affected by the sebacate content rather than the DP of chain segments. The independent Tg of sebacate in the copolymers was not detected by DSC, i.e., the two polymer chains were compatible without phase separation. Phase separation was only observed in the rheometric spectrum of a 1 : 1 blend of the two homopolymers. The sebacate, being compatible with the isophthalate, had a plasticizing effect upon the polyarylate, which resulted in an improvement in toughness of the copolymers.

Shear and craze development in the fatigue of ductile amorphous polymers

The competitive interplay between shear and craze deformation in the fatigue of ductile amorphous polymers leads to the formation of intricate fatigue crack shapes and stable crack growth. The craze/shear dual deformation mode is expressed in a unique crack tip plastic zone, which has been observed in polycarbonate, polysulfone, a polyarylate block copolymer and a polyestercarbonate copolymer. The fatigue crack growth resistance in these polymers is high, and factors which affect the relative ease of shear flow and crazing are expected to affect their fatigue endurance.