Study on the Coupling of Mutual Diffusion to Viscoelasticity in Polymer Solutions

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In this work, we have, firstly, confirmed the validity the validity of our theory on the coupling of mutual diffusion to viscoelasticity in moderately concentrated polymer solutions, thereby affording a means to determine the diffusion coefficient D, friction coefficient ζ, rubbery plateau modulus L_0, and terminal relaxation time γ_m from the autocorrelation function g^ <(2)>(t) obtained from dynamic light scattering by using the discrete spectrum analysis of g^<(2)> (t) combined with the cumulant analysis. The method has been successively applied to the solutions of some synthetic polymers and also of "living" polymers, i.e., polymer-like micelles. The main results thus obtained are summarized as follows:1) For all the polymer solutions examined, ζ increases with increasing concentration c following the same power-law dependence irrespective of the polymer species, molecular weight M_ω, and solvent quality, indicating that the solvent dependence of D as a function of c is ascribed to that of the osmotic compressibility.2) The L_0 vales sre proportional to c^2 and smoothly connected to the literature values of respective polymers at the bulk state. The results imply that the concept based on the rubber elesticity theory holds not only for polymer concentrates but for rather dilute polymer solutions.3) γ_m is proportional to M^<3.4>_ω irrespective of the polymer-solvent system in good accordance with the 3.4th power-law for the steady-state viscosity.4) Lecithin forms spherical micelles in cyclohexane and the micelles change their shape to the cylindrical with including water. The length of the cylinder is lengthened as the water content is increased, by keeping the distance between lecithin molecules constant.5) The surfactant C_<12>E_6 forms prolate ellipsoidal micelles in aqueous solutions. The micellar solutions exhibit viscoelastic behavior due to network formation by stringlike micelles at large c.