Diffusion of Polystyrene Latex Spheres through Isotropic Rigid Rod Polymer Solutions

Abstract

The diffusion of highly cross-linked polystyrene latex spheres of radii 0.152 and 0.208 μm through solutions of poly(γ-benzyl-l- glutamate) (PBLG) has been studied by dynamic light scattering (DLS). The solvent used was dimethylformamide (DMF), in which PBLG adopts a rigid rodlike α-helical conformation. Tracer diffusion coefficients of the spheres in solutions of long rods (L ≈ 159 nm) were larger than predicted from the Stokes−Einstein equation. These positive deviations from the Stokes−Einstein equation are consistent with the theory of Auvray (J. Phys. 1981, 42, 79), which predicts the presence of a rod monomer depletion layer locally surrounding the spheres that extends a distance ≈ L from the surface of the sphere. The results are also consistent with the experimental work of others concerning depletion of stiff polymers near surfaces. Sphere tracer diffusion coefficients in solutions of smaller rods (L ≈ 48 nm) approximately follow the Stokes−Einstein equation. In this system, depletion effects are expected to be much smaller. Fits of the sphere diffusion data to the equation D/D 0 = exp(−αc υ) yielded values of υ = 1−1.1, which exceed those predicted by theory. We were also able to estimate translational diffusion coefficients of the PBLG in the ternary rod/sphere/solvent systems by employing very short sample times in the DLS experiment.

Rotational dynamics of colloidal tracer spheres in suspensions of charged rigid rods

“…This explains the increase of the deviation from SED scaling with increasing host particle volume fraction. 11 As seen in Fig. 7, the ionic strength of the host fluid strongly affects the applicability of SED scaling.…”

“…Rodlike particles are also known to very effectively retard particle transport. Both theoretical 4 -7 and experimental [8][9][10][11][12] work has been done on the translational diffusion of spherical tracer particles in host suspensions of rods, showing that host rods retard tracer diffusion at much lower volume fractions than host spheres. Rotational diffusion of tracer spheres in rod suspensions has, to our knowledge, not been studied yet.…”

Continuous Preparation of Size-Controllable BaTiO3 Nanoparticles in a Rotor–Stator Spinning Disk Reactor

“…Therein, the detection principle of DLS is to irradiate the particles with a laser and calculate the size of nanoparticles by analyzing the intensity of scattered light. The calculation method is based on the Stokes–Einstein formula where d h is the hydraulic diameter, k B is Boltzmann’s constant, T is absolute temperature, η 0 is the viscosity of the medium, and D is the coefficient of diffusion. The test temperature is constant at 25 °C.…”

Dynamic fluorescence microscopy as a feasible technique for estimating the diffusion coefficients of small particles in the presence of additives

“…The dynamics of colloids have been investigated in threedimensional samples, mainly using dynamic light-scattering techniques [2][3][4][5][6]. The very rapid progress of computer and imaging technology has lead to a revival of the early studies of Brown, this time using modern microscopy techniques and digital image processing [7].…”