SOLUTION PROPERTIES OF POLYISOBUTYLENE INVESTIGATED BY USING DYNAMIC AND STATIC LIGHT-SCATTERING AND PULSED FIELD GRADIENT NMR

The solution properties of the flexible polymer polyisobutylene (PIB) with chloroform as solvent are compared with those of polystyrene (PS) in good solvents over a broad concentration range extending from dilute through the semidilute regime. The methods included both static and dynamic light scattering, and frictional coefficients were evaluated by using pulsed field gradient NMR. The latter technique was also used to obtain self-diffusion coefficients for PIB in the THETA-solvent benzene (24.5-degrees-C), which is isorefractive with PIB. The "universal" ratio rho = R(g)/R(h) is unusually large (rho almost-equal-to 1.77) compared with the value for PS in good solvents (almost-equal-to 1.5), showing a possible difference in draining behavior. In semidilute solution, the dynamic length scales for PS and PIB are identical at the same weight concentration even though the different entanglement densities might have been expected to make themselves felt. Small systematic deviations from the behavior predicted by renormalization group theory exist and are similar for both types of chain.