Studies on Depletion Layer of Probe Particles in the System of Poly(vinyl acetate)/Dimethyl Sulfoxide by Dynamic Light Scattering

In In the system of poly(vinyl alcohol) (PVA)/dimethyl sulfoxide, the refractive index of polymer was very well matched to that of solvent and thus its scattered intensity could be minimized. After adding small amount of polystyrene latex particle (nominal diameter 200 nm), diffusion behavior of only probe particle was investigated against the concentration of polymer matrix by means of dynamic light scattering. The polymer concentration dependence of its reduced diffusion coefficient was able to be analysed with the stretched exponential function of the reduced concentration C[eta]. In very dilute concentration regime, the depletion layer kept constant but at the early semi-dilute regime of 1 <= C[eta]<= 2.5, the concentration-dependent exponent of depletion layer delta was appeared to be -0.8 which was very close to theoretical one of -0.85. However it was also observed at the higher concentration that its layer thickness decreased more abruptly than theoretical expectation and this phenomenon was ascribed to Oosawa type attractive interaction between adjacent latex particles.