Intermolecular interactions in random copolymer systems depend on the copolymer composition as being observed as a miscibility window in the random copolymer blends. The copolymer composition dependencies of the Flory‐Huggins χ parameter and the heats of mixing ▵HM(∞) at infinite dilution were studied for the solutions of poly(methyl methacrylate‐ran‐n‐butyl methacrylate) (MMAnBMA) in cyclohexanone (CHN). The copolymer composition dependencies of χ obtained from osmotic pressures and of ▵HM(∞) measured with a microcalorimeter were concave curves. This suggests that the random copolymers MMAnBMA interact with CHN more attractively than do the homopolymers PMMA and PnBMA. This is caused by the repulsion effect between the MMA and nBMA segments. The equation‐of‐state theory extended to the random copolymer systems by us reproduced fairly well these thermodynamic properties. The χ parameter for the PMMA/PnBMA blends was calculated using the equation‐of‐state theory with the MMA/nBMA intersegmental parameters employed for the above random copolymer solutions in CHN. The χ value calculated thus was in satisfactory agreement with that obtained from the random copolymer solutions using the Flory‐Huggins theory extended to multicomponent systems. © 1996 John Wiley & Sons, Inc.
It has been so far reported that some polymer blends containing random copolymers can be miscible in a certain range of copolymer compositions even though the combinations of their corresponding homopolymers are immiscible. On the other hand, according to theory, there may exist some copolymer blends that are immiscible in a certain range of copolymer compositions even though their corresponding homopolymers are miscible with each other. For real blends with a possibility of such an immiscibility region, the dependence of miscibility on the copolymer composition was observed at the blend ratio 1/1. Poly(viny1 chloride-co-vinyl acetate) copolymers (VC-VAc) were immiscible with poly(n-butyl methacrylate-co-isobutyl methacrylate) copolymers (nBMAiBMA) in a certain range of copolymer compositions of nBMASiBMA, though every pair of VC-VAc copolymer/nBMA homopolymer, VC-VAc copolymer/iBMA homopolymer, and nBMA homopolymer/iBMA homopolymer was miscible.
Invertase was ionically immobilized on the poly(ethylene-co-vinyl alcohol) hollow fiber inside surface, which was aminoacetalized with 2-dimethylaminoacetaldehyde dimethyl acetal. Immobilization and enzyme reaction were carried out by letting the respective solutions pass or circulate through the inside of the hollow fiber, and the activity of invertase was determined by the amount of glucose produced enzymatically from sucrose. Immobilization conditions were examined with respect to the enzyme concentration and to the time, and consequently the preferable conditions at room temperature were found to be 5 microg/mL of enzyme concentration and 4 h of immobilization time. Under those conditions the immobilization yield and the ratio of the activity of the immobilized invertase to that of the native one were 89 and 80%, respectively. For both repeating and continuous usages, the activity fell to ca. 60% of the initial activity in the early stage and after that almost kept that value. The apparent Michaelis constant K(m)(') for the immobilized invertase decreased with increasing the flow rate of the substrate solution, to be close to the value for the native one. Furthermore, the possibility of the separation of the enzymatically formed glucose from the reaction mixture through the hollow fiber membrane was preliminarily examined.
The Flory interaction parameters χ for blends of random copolymers consisting of binary combinations of methyl methacrylate (MMA), n-butyl methacrylate (nBMA), and isobutyl methacrylate (iBMA) monomers were calculated using the Flory equation-of-state theory with modified combining rules extended to random copolymer systems. In order to determine the intersegmental or intermolecular parameters necessary for the calculation of χ for the blends, osmotic pressures, heats of mixing at infinite dilution, and excess volumes of mixing for solutions of the methacrylate random copolymers in cyclohexanone were measured, and the equation-of-state theory was applied to these solutions. Using the intersegmental parameters thereby determined, the theory gives U-shaped curves for the temperature dependence of χ for the blends. Namely, the theory shows that miscibility of these polymer blends is of the upper critical solution temperature type, which is consistent with the miscibility results obtained experimentally in our previous work. The interaction parameters χ calculated for PiBMA/PnBMA were much smaller than those for PMMA/PiBMA and PMMA/PnBMA. This result is also consistent with the experimental results of miscibility. The calculated χ parameters were compared with those evaluated using two other methods, i.e., from the dependence of miscibility on the copolymer composition of the random copolymer blends and from the osmotic pressures for the random copolymer solutions. It was found that the χ values obtained using all three methods were nearly the same.
ABSTRACT:Previously miscibility for the blends of poly(vinyl chloride-stat-vinyl acetate) (VCV Ac90, containing 90 wt% ofVC) with poly(isobutyl methacrylate-stat-n-butyl methacrylate) (iBMAnBMA) was found to be like a so-called immiscibility window. In this work, the temperature dependence of the Flory-Huggins x parameter was calculated for the VCVAc90/ iBMAnBMA blends using the Flory-type equation-of-state theory extended to random copolymer systems. The equation-ofstate parameters necessary for calculation of X was determined using the experimental results of osmotic pressures and heats of mixing for solutions of these polymers in cyclohexanone (CHN). The temperature dependence of x was a monotonically increasing function over all the copolymer compositions of iBMAnBMA copolymers, and there existed a range of copolymer compositions in which x for the copolymer blends VCV Ac90/iBMAnBMA was positive though xs for both homopolymer blends VCV Ac90/PiBMA and VCV Ac90/PnBMA (where VCV Ac90 was regarded as a homopolymer) were negative. This corresponds qualitatively to miscibility behavior observed for the present copolymer blends. It was concluded that miscibility behavior in the present copolymer blends is one of two types of immiscibility windows classified previously by us.KEY
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