Intrinsic viscosity of aminoacetalized polyvinyl alcohol sulfate in 1/10 N potassium sulfate solution
Authors: Matsumoto Masakazu , Eguchi Tamotsu 
Published: April 2003

The intrinsic viscosity of the sulfate of aminoacetalized polyvinyl alcohol (Am‐PVA) in N/10 K2SO4 solution has been studied to disclose the influence of the number of ionic substitutents on the intrinsic viscosity of the polymer. The number of ionic substitutents is easily changed by controlling the degree of aminoacetalization, which is determined by a selection of the conditions of aminoacetalization. β‐Cyclohexylamino n‐butyraldehyde dimethylacetal, CH3(C6H11NH)CH·CH2·CH(OCH3)2, and β‐cyclohexylamino‐n‐propylaldehyde dimethylacetal, (C6H11NH)CH2·CH2·CH(OCH3)2, were used as aminoacetals. The aminoacetalization reaction was carried out in a system of aminoacetal, polyvinyl alcohol (PVA), sulfuric acid, and water. The reaction product was purified by dialysis, and the degree of aminoacetalization was estimated from the nitrogen content as given by the semimicro Kjeldahl method. The PVA was used unfractionated and its degree of polymerization, as determined by the viscosity method, was found to be between 900 and 2400. The solution viscosity was measured in an Ostwald viscometer designed to reduce the kinetic energy term for which a correction was made. It was first ascertained that the viscosity in N/10 K2SO4 solution was not influenced by the rate of shear in the range of our experiment. The intrinsic viscosity was found from linear extrapolation, a linear relation between ηsp and c, being well realized in the concentration range from 1.5 to 9 g./l. The intrinsic viscosity increased with the degree of aminoacetalization in an S‐shaped fashion. Compared to the same degree of aminoacetalization, Sakurada‐Houwink's equation [η] = KPa was found to hold well at each degree of aminoacetalization, and the index a was found to increase with the degree of aminoacetalization. The volume expansion α3 of the polymer in the solution was estimated from [η]M/[η]θM0 according to Flory's theory, in which M is the molecular weight of the sulfate of Am‐PVA, M0 the molecular weight of each original PVA, [η] the intrinsic viscosity of the sulfate of Am‐PVA, and [η]θ is the mean intrinsic viscosity of each original PVA in Flory's unperturbated state. The viscosity in a mixture of acetone (35.2%) and water (64.8%) was used for [η]θ, its value being calculated from [η]θ = 1.06 P1/2, having reference to Sakurada's report. Then (α5 − α2/M1/2) was calculated and plotted against the degree of aminoacetalization x. It was found that these points fall on one curve, independently of the degree of polymerization of the original PVA. When [(α5 − α3)/M1/2]x − [(α5 − α3)/M1/2]0 was plotted against x in a log‐log scale (we are subtracting the value [((α5 − α3)/M1/2]0 for PVA) it was found that a linear relation between them holds well independently of the degree of polymerization of PVA. The empirical formula [(α5 − α3)/M1/2]x − [(α5 − α3)/M1/2]0 = Axn was thus obtained. In both Am‐PVA's n is 1.45, but A differs slightly. When the ionic strength is constant, {[(α5 − α3)/M1/2]x − [(α5 − α3)/M1/2]0} should be proportional to x2/(M/r)3/2 by Flory's theory of polyelectrolytes. The fact, therefore, that the former was found to be proportional to x1.45 in our result suggests that (M/r)3/2) is not constant but may be changed by the degree of aminoacetalization, first, because the volume effect of the cyclohexyl‐aminoacetal group introduced cannot be disregarded, and second, because the molecular weight M increases with aminoacetalization. The overlapping of the two effects apparently yields the exponent 1.45.