Viscosity-concentration results in the moderately concentrated range for four samples of polyisobutylene (molecular weights of 1.3 x 104 to 1.0 x 106) in cyclohexane (concentrations up to 4.7 g./dl.) and in benzene (concentrations up to 7.0 g./dl.) at 24°C. (a theta solvent) showed molecular weight and goodness of solvent dependencies similar to those reported earlier for three other polymers. For polyisobutylene, polystyrene, and a copolymer of styrene and methyl methaerylate in good solvents, viscosity-concentration data plotted as ηsp. C[η] vs. k′[η]C fit a single curve. The linear region of this curve suggests that the Huggins equation is useful to C[η] values up to ≈1 for good solvents. Viscosity-concentration data which were less steep than curves corresponding to Baker n values of 3.5 also fit a single curve. Values of k′ for polyisobutylene in a good solvent decrease with molecular weight as noted for polystyrene. For four polymers in good solvents, the value of k′α for each system is very nearly constant. Data for polyisobutylene and polystyrene in good solvents could also be correlated as log ηR vs. log CM0.68 as proposed by Ferry and co-workers. However, values of a in the Mark-Houwink equation must be near 0.68 for good correlations with CM0.88. Theta solvent data where a = 0.50 can not be correlated in this way. © 1968.


Chemical and Biochemical Engineering

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Article - Journal

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01 Jan 1967