Monitoring coalescence behavior of soft colloidal particles in water by small-angle light scattering

Abstract

The fractal dimension (D f ) of the clusters formed during the aggregation of colloidal systems reflects correctly the coalescence extent among the particles (Gauer et al., Macromolecules 42:9103, 2009). In this work, we propose to use the fast small-angle light scattering (SALS) technique to determine the D f value during the aggregation. It is found that in the diffusion-limited aggregation regime, the D f value can be correctly determined from both the power law regime of the average structure factor of the clusters and the scaling of the zero angle intensity versus the average radius of gyration. The obtained D f value is equal to that estimated from the technique proposed in the above work, based on dynamic light scattering (DLS). In the reactionlimited aggregation (RLCA) regime, due to contamination of small clusters and primary particles, the power law regime of the average structure factor cannot be properly defined for the D f estimation. However, the scaling of the zero angle intensity versus the average radius of gyration is still well defined, thus allowing one to estimate the D f value, i.e., the coalescence extent. Therefore, when the DLS-based technique cannot be applied in the RLCA regime, one can apply the SALS technique to monitor the coalescence extent. Applicability and reliability of the technique have been assessed by applying it to an acrylate copolymer colloid.

Water‐Dispersible, Ligand‐Free, and Extra‐Small (<10 nm) Titania Nanoparticles: Control Over Primary, Secondary, and Tertiary Agglomeration Through a Modified “Non‐Aqueous” Route

“…Correspondingly, log( I) versus log( q ) plots do not provide useful information about D f (see Supplementary Information, Figure 3SI). An alternative SLS approach would use the relationship between I ( 0 ) (intensity at q = 0) and the ratio ( R p being the radius of the primary particles), whose slope in a log–log plot would again provide the fractal dimension . However, this approach is rather cumbersome (a Zimm plot per time point) and is affected by significant errors in the estimation of at early time points, due to the contribution of primary particles.…”

Morphology of Shear-Induced Colloidal Aggregates in Porous Media: Consequences for Transport, Deposition, and Re-entrainment

“…The SALS instrument used in this work (Mastersizer 2000, Malvern, UK) has a working angle range θ = 0.02−40°, a wavelength of incident light λ 0 = 633 nm, and an intensity acquisition frequency of 1000 s −1 . Details of the SALS system can be found elsewhere, 40 and the calculations for estimating ⟨R g ⟩ are described in the Supporting Information (SI). SALS measurements demonstrate that the chosen water chemistry creates unfavorable conditions for aggregation in our suspension.…”