Hidematsu Suzuki

Temperature dependence of limiting viscosity number and radius of gyration of cellulose diacetate in acetone

Abstract Acetone solutions of a cellulose diacetate fraction were studied by viscosity and light scattering methods over the range 12.6–50.3 2 . The temperature dependences of the limiting viscosity number [η], the mean-square radius of gyration 〈s 2 〉, and the second virial coefficient A 2 were determined. The unperturbed mean-square radius of gyration 〈s 2 〉 o and the expansion factor α, were estimated by using theoretical relations to the interpenetration function. It was found that dln 〈s 2 〉 o /d T is −6.4 × 10 −3 deg −1 , while α, is close to unity over the whole temperature range studied. The viscosity results are interpreted to show that the draining effect is not negligible and the Flory viscosity parameter Φ slightly increases with increasing temperature. It is finally concluded that the value of −6.9 × 10 −3 deg −1 for dln [ η ]/d T can be ascribable to the rapid decrease in 〈s 2 〉 o .

Shear‐Rate Dependence of the Intrinsic Viscosity of Flexible Linear Macromolecules

Shear‐rate dependence of the intrinsic viscosity has been studied on polystyrene in four different solvents by using a Zimm—Crothers rotational viscometer and Ubbelohde viscometers. The former viscometer was employed particularly for measuring zero‐shear intrinsic viscosity [η]0. The results are summarized in terms of the [η]/[η]0 versus generalized rate of shear β=([η]0ηsM/RT)G, where ηs is the solvent viscosity, M the solute molecular weight, G the rate of shear, and others have usual significance. It has been found that, (i) at the values of β below 0.1, [η] is practically independent of rate of shear (or shear stress); (ii) the non‐Newtonian effect does exist even in θ conditions; and (iii) at the values of β below 2, the [η]/[η]0‐vs‐β curves of the systems with different molecular weights and in different solvents give a single composite curve, which fairly well resembles to the curve of a prolate ellipsoid with the axial ratio p=3.

Shear‐Rate Dependence of the Intrinsic Viscosity of Flexible Linear Macromolecules. II. Solvent Effect

Measurements of the shear‐rate dependence of the intrinsic viscosity [η] were made on polystyrenes in several solvents, each of which differs in solvent power and solvent viscosity. Low‐shear capillary viscometers of the Maron–Belner type were used: shear stresses can be varied continuously from about 10 to a few tenths of a dyn/cm2, which is low enough to measure the zero‐shear intrinsic viscosity [η]0. The effect of excluded volume on the behavior of [η] / [η]0‐vs‐β (the generalized shear‐rate) curve was examined. The curves at and near the θ condition resemble that of Saito–Scheragas prolate ellipsoid with axial ratio p = 2, and those in good solvents resemble that of p = 3 ellipsoid; the variation with solvent power is not so large as the theory of either Fixman or Chikahisa predicts. In the region of moderate to large β, the [η] / [η]0‐vs‐β curve decreases continuously with increasing β, as contrasted to the behavior of the ellipsoid, which levels off rather rapidly. The non‐Newtonian behavior is pr...

Light-scattering study on cellulose diacetate in 2-butanone

Abstract Light-scattering measurements were carried out on three well-fractionated samples of cellulose diacetate (degree of substitution = 2.46) in acetone at 25°C and in 2-butanone at 30–60°C. For the system cellulose diacetate-2-butanone, the theta temperature, Θ, has been quoted as 37°C from cloud-point measurements; it was intended to examine further 2-butanone as a theta solvent. The value of Θ, defined as the temperature at which the second virial coefficient vanishes, was found to be 50°C. This difference in Θ was attributed to association of the dissolved polymer molecules. On the other hand, the weight-average molecular weights obtained in 2-butanone at 50°C were in accord with those determined in a good solvent, acetone. It was established that 2-butanone was a theta solvent for cellulose diacetate with Θ = 50°C. The molecular dimensions observed in 2-butanone were however unreasonably large. Therefore, determinations of the unperturbed dimensions and other conformational parameters in this solvent are withheld. Solution stability and association were examined by light scattering. It was deduced that the difficulty in dissolving the polymer in 2-butanone arose from the copolymeric nature of cellulose diacetate.

Lower critical solution temperature study on cellulose diacetate-acetone solutions

Abstract Cloud points of acetone solutions of four well-fractionated samples of cellulose diacetate (degree of substitution = 2.46) have been measured at elevated temperatures. The molecular weight of the fractions ranged from 3.76 × 104 to 17.5 × 104. The lower critical solution temperature (LCST) was determined as the minimum of each cloud-point curve. The results adequately satisfy the Shultz-Flory relation with ΘL = 428 K and ψ1.L = −0.94; here ΘL is the Flory theta temperature and ψ1.L is the entropy parameter of dilution; subscript L refers to the LCST. The results have been analysed by an equation-of-state theory. The molecular-weight dependence of LCST is compared with the theoretical prediction of Delmas and Patterson, the temperature dependence of the interaction parameter χ1 being estimated therefrom. Although the absolute predicted values for LCST are low, the equation-of-state parameter obtained suffice to confirm the observation in a previous study that no phase separation occurs at low temperatures.

An estimation of the temperature dependence of the excluded-volume integral

Abstract Lower critical solution temperatures (LCST) of trans-decalin solutions of polystyrene were measured on a newly built electric thermostat, the theta point ΘL associated with the LCST being determined as 662 K. By use of this result together with the literature data for the ordinary theta point (ΘU) and the entropy of dilution parameter, the excluded-volume integral B(T) was estimated in terms of the Eichinger method over the temperature range ΘU to ΘL. This enabled us to calculate the excluded-volume variable z as 0.770 C M ′ B(T) M w 0.5 . Here, CM′ is a numerical factor specific for a given polymer-solvent system and M w is the weight-average molecular weight. Using the z values calculated from the above expression, we analysed the data on dilute solution properties of polystyrene reported by Berry and by Inagaki et al. It was found that the Domb-Barrett and the Suzuki equations for αs (the linear expansion factor for the radius of gyration) were in good agreement with Berrys data of light scattering. The first coefficient k1 in the series αν3 = 1 + k1z + … (αν: the hydrodynamic expansion factor) was experimentally evaluated as 1.70. Furthermore, a conversion of the Suzuki equation for α5 into that for αν with this k1 value was found to account quite satisfactorily for the viscosity behaviour observed by Inagaki et al.

Isotropic and anisotropic scattering from polyethylene during crystallization

Abstract A light-scattering method for determining the optical anisotropy of large molecules is considered in detail. An application of the method is demonstrated to linear polyethylene while isothermally crystallizing in p-xylene solution. The polyethylene crystals formed are characterized as anisotropic thin discs having an optical anisotropy of 0.4–0.6.