Dynamics in concentrated polymer solutions studied using dynamic light scattering
Concentrated solutions (volume fraction 0.1–0.9) of polystyrene (PS) in toluene and of polybutylacrylate (PBA) in dioxane have been examined using dynamic light scattering (DLS) as a function of angle and temperature. With PS there is a pronounced maximum in the cooperative diffusion coefficient (D c) at about Φ=0.5 as the glassy state is approached. By contrast, with PBA, which has a very low T g, there is a crossover to a stronger concentration dependence for D c, which is attributed to an increase in solvent mobility. In the PS/toulene system at Φ=0.78 a transition is noted between the diffusion mode and the main relaxational mode. At 17°C q-independence is observed and at 50 °C q 2-dependence. At Φ=0.89, both relaxations are observed simultaneously in the DLS time window, the slower process being a structural relaxation.
Key wordsPhoton correlation polystyrene concentrated solutions relaxation times
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