Dynamics in Solutions of Associating Statistical Copolymers

Abstract

The association of styrene−methyl methacrylate statistical copolymers in the selective solvent acetone (a thermodynamically good solvent for poly(methyl methacrylate and bad for polystyrene) was examined by static and dynamic light scattering methods. In dilute solutions, the dynamics was dominated by a single fast mode, whereas in semidilute solutions two modes were generally seen, with fast and slow mean relaxation times. The fast dynamic mode was related to the cooperative diffusion mode. The slow mode was associated with dynamics of polymeric clusters formed by the random association process. Experimental results were interpreted in terms of the coupling model of partly penetrating polydispersed clusters formed by random association of copolymers.

Director dynamics in liquid-crystal physical gels

“…The data for the LC gels qualitatively resemble those observed from previous light-scattering studies of associating polymers, [23][24][25][26][27][28][29] with the appearance of slow relaxation modes above a critical concentration and highly stretched intensityautocorrelation functions with a strong q-dependence. However, in the present study, the scattered light arises primarily from fluctuations in the orientation of the nematic director, not density fluctuations as in the previous lightscattering studies of gelled systems [23][24][25][26][27][28][29] .…”

“…However, in the present study, the scattered light arises primarily from fluctuations in the orientation of the nematic director, not density fluctuations as in the previous lightscattering studies of gelled systems [23][24][25][26][27][28][29] . Therefore, structural changes such as micellar diffusion or concentration fluctuations in the polymer network are revealed indirectly by their effect on the nematic-director dynamics.…”

“…Indeed, the q-dependence of the slow relaxation appears to be stronger than q 2 (or sin 2 h s /2) for small wavevectors (or low h s ), and it is reminiscent of hindered relaxational dynamics in colloidal glasses and associative polymers. [23][24][25][26]28,30 We propose that the nematic director is coupled to the associated gel structure, yielding long-lived orientational fluctuations. The nematic director can relax via the fast relaxation mode only to a certain extent, due to a coupling to the polymer-gel structure.…”

Dynamics of amylopectin in semidilute aqueous solution

“…Nemoto et al [29] found that the line-width of slow relaxation caused by the associated large cluster was independent of q. However, Koňák et al [21] found that the line-width of slow relaxation originating from the associated large cluster could be scaled to q a , a varying from 2.0 to 5.0 with varying the concentration. The slow relaxation mode originating from the associated cluster was found in potato amylopectin solution when C/C* w 2.5.…”

Blends of PDMS and random copolymers of dimethylsiloxane and methylphenylsiloxane: Phase separation in the quiescent state and under shear

“…Dynamic light scattering measurements 13) were reported for the system acetone/poly[styrene-ran-(methyl methacrylate)], where acetone corresponds to the segments of homopolymer A and interacts favorably with the methyl methacrylate units of the copolymer (analogue of the A segments of the present model copolymer A-ran-B) whereas it constitutes a precipitant for the styrene units (analogue of the B segments). The authors conclude that a slow mode they observe in semidilute solutions is due to the dynamics of polydispersed clusters formed by random association of copolymers.…”