Dynamic Viscoelasticity of Polymer Solutions

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The dynamic storage and loss moduli of polymer solutions will be measured using an extremely sensitive resonator instrument which has been constructed in the principal investigator's laboratory. For dilute polymer solutions, the intrinsic moduli will be obtained by concentration extrapolation of measured moduli; these moduli reflect the molecular relaxation processes of the polymer chain. Linear, star, and cyclic random- coil polymers of matched molecular weights will be studied in dilute solutions; polymers in solvents with varying thermodynamic quality or specific solvent-polymer interactions; polymer with side chains which modify their molecular flexibility; block copolymers where the blocks can be preferentially solvated; polyelectrolytes; and polymers which undergo reversible transformations of structural conformation. In addition, a systematic study will be undertaken with respect to modification of chain relaxations caused by initial chain interactions at low concentrations where chains just begin to overlap. For all well- characterized polymers will be used so that the results will be suitable for testing theoretical predications and for comparisons to complementary experiments.