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Dissolution (mixing or melting) of inhomogeneities formed during spinodal decomposition in binary polymer mixtures is studied both experimentally and theoretically. The details of the dissolution experiment with time-resolved light scattering on polystyrene/poly(vinylmethylether) are presented. The theoretical approach differs from that of Langer, Bar-on, and Miller in the way the fluctuations are treated in the nonlinear theory, and in the details of the calculations arising from the chain connectivity (polymer effect). The effect of mode coupling arising from nonlinearity on the relaxation rate is discussed. It is found both experimentally and theoretically that the wave number corresponding to peak intensity decreases in time asymptotically following a t-0.5 power law. [ABSTRACT FROM AUTHOR]

A deviation from mean-field behavior is observed in the static susceptibility and correlation length measured with small angle neutron scattering as a function of temperature near the phase boundary of a relatively low molecular weight critical polymer mixture. The possibility of a fluctuation influenced crossover from mean-field to nonmean-field behavior is considered. [ABSTRACT FROM AUTHOR]

Small-angle neutron scattering was used to observe the relaxation of the structure factor from a smaller to a larger fluctuation state after a temperature jump within the one-phase region of a miscible polymer blend. The blend studied is a 60/40 by weight mixture of a hydrogen bonded polymer blend which consists of hydroxy modified deuterated polystyrene and poly(butylmethacrylate). A peak clearly evolved during the transition from the initial state at Ti to the final state at Tf as predicted by linear as well as nonlinear theories. This relaxation process, which took more than 10 h, could be represented reasonably well by a simple linear approximation of the Cahn–Hilliard–Cook (CHC) theory without involving nonlinear calculations for the evolution of the dynamic structure factor. The measurement offers an alternative method for estimating the order parameter relaxation rate in the one-phase region. Also, this demonstrates experimentally the correct relaxation (to a higher fluctuation state) mechanism predicted by the linear theory of CHC type. © 1996 American Institute of Physics. [ABSTRACT FROM AUTHOR]

[S0021-9606(97)00230-4] [ABSTRACT FROM AUTHOR]