Effect of Solvent Quality on the Diffusion of Polystyrene Latex Spheres in Solutions of Poly(methyl methacrylate)

Abstract

Dynamic light scattering has been used to study the diffusion of polystyrene (PS) latex spheres (≈0.2 μm radius) in poly(methyl methacrylate) (PMMA) solutions at 25 °C. The weight-average molecular weight of the PMMA was 350 000. The sign and magnitude of the deviations from the Stokes−Einstein (SE) equation varied dramatically with solvent quality. Positive deviations from SE behavior (ηD sphere/η0 D 0 > 1) were observed in good solvents for PMMA, such as dimethylformamide (DMF) and tetrahydrofuran (THF). We argue that these positive deviations are a result of a layer of solution locally surrounding the latex spheres that is rich in solvent and deficient in PMMA. This “depletion layer” is likely caused by a combination of entropic repulsion between the matrix PMMA and the latex spheres, and most importantly the immiscibility of PMMA and PS. A negative deviation (ηD sphere/η0 D 0 < 1) by almost of factor of 3 from the SE equation was observed in a dioxane−water mixed solvent, which is a ϑ-solvent for PMMA at 25 °C. PMMA adsorption onto the latex spheres is argued to occur under these unfavorable solvent conditions. At high matrix concentrations, entanglements of the adsorbed PMMA with free PMMA in solution likely occur. A very slow relaxation mode, in addition to the mode associated with sphere diffusion, was present in the CONTIN analyses of the PMMA/PS latex/dioxane−water system. It is possible that this mode is due to PMMA clusters, or less likely, bridged PS latex moieties.

Particulate Hematite Diffusion in Sodium Polyacrylate Solutions. The Effect of Ionic Strength

“…Gold et al (27) found the diffusion of polystyrene latex particles in poly(methyl methacrylate)-dioxane-water solutions to exhibit a double-exponential decay of the autocorrelation function. Mustafa and Russo (28) and Brown and Rymden (9) studied polystyrene latex diffusion in high-molecular-weight hydroxypropylcellulose solutions and found the autocorrelation functions to contain two relaxation times.…”

Charge and Size Dependence of Liposome Diffusion in Semidilute Biopolymer Solutions

“…To quantify the difference between microscopic and macroscopic viscosity the SE ratio, [ D c ( C p ) η p ]/[ D c (0) η 0 ], is introduced. Both positive deviations from the SE behavior14, 40 – where [ D c ( C p ) η p ]/[ D c (0) η 0 ] > 1 – and negative deviations41, 42 – for which [ D c ( C p ) η p ]/[ D c (0) η 0 ] < 1 – have been reported. Although the corresponding mechanisms are unclear, it is generally accepted that the deviations result from the direct or indirect interaction between the polymers and the particles, and that other effects such as microstructure, polymer adsorption or cluster formation might gain significance.…”

“…Although the corresponding mechanisms are unclear, it is generally accepted that the deviations result from the direct or indirect interaction between the polymers and the particles, and that other effects such as microstructure, polymer adsorption or cluster formation might gain significance. Details about possible mechanisms are reviewed by Gold and co‐authors 42…”

Diffusion of hairy polymeric micelles in a homopolymer solution

“…The diffusion of polymeric particles or polymer chains in another polymer solution has received considerable attention [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. Such a system consists of a sphere particle or labeled polymer, a matrix polymer and a solvent.…”