Salt-Induced Aggregation of Polystyrene Latex Particles in Aqueous Solutions of a Hydrophobically Modified Nonionic Cellulose Derivative and Its Unmodified Analogue

Abstract

The structure and kinetics of clusters formed in the salt-induced (0.7 M NaCl) aggregation processes of polystyrene latex particles in the presence of various amounts of ethyl(hydroxyethyl)cellulose (EHEC) or the hydrophobically modified analogue (HM-EHEC) have been investigated with the aid of light scattering measurements. Under all conditions, both with and without polymer, the aggregating clusters are well described by a fractal geometry with a fractal dimension of 2.1. Three stages can be discerned in the salt-induced aggregation process of bare latex particles. In the early stage, the time evolution of the hydrodynamic radius R h can be described by a power law R h ∝ t 0.04, followed by a steep transition zone and an exponential growth at long times. In the presence of polymer, the slow cluster size growth can be described by the above power law over the whole considered time domain. The value of the power law exponent is independent of polymer concentration and hydrophobicity of the polymer. The results show that only a small amount of adsorbed polymer is needed to slow the rate of the aggregation process. The results show that both polymers adsorb to the latex particles, but the adsorption is more pronounced for the hydrophobically modified polymer.

Polylactide-co-glycolide-rifampicin-nanoparticles efficiently clearMycobacterium bovisBCG infection in macrophages and remain membrane-bound in phago-lysosomes

“…Table 1 summarizes the data on a selection of NPs with respect to rifampicin and coumarin-6 loading, size and b-values (giving information about the particle size distribution) determined from dynamic light scattering and zeta potential. More details about the analyses of the DLS data have been given previously (Kjøniksen et al, 1999). These results confirm that the NPs are slightly negatively charged (under conditions of 0.15 M NaCl) and are uniform in size distribution.…”

Adsorption of cellulose derivatives on flat gold surfaces and on spherical gold particles

“…A conspicuous feature is the high amount of adsorbed HM-HEC, on both surfaces, in comparison with that of HEC. Previous adsorption studies [20][21][22] of aqueous solutions of EHEC and HM-EHEC have revealed that the more hydrophobic counterpart has usually a higher affinity to adsorb onto different substrates. An interesting feature is the fact that a higher surface coverage is observed for gold surfaces with citrate-layer, and this effect is more pronounced for HEC than HM-HEC (see Fig.…”

“…Hydroxyethylcellulose (HEC), on the other hand, is essentially a hydrophilic polymer and this cellulose derivative displays rather weak thermoresponsive properties. It has been established in previous papers that a large amount of EHEC is adsorbed onto polystyrene latex particles [20][21][22]. If we take into account that the EHEC polymer contains hydrophobic microdomains in addition to regions of hydrophilic nature, one would expect the adsorption behavior to be altered when surfaces of different hydrophobicity are employed and the polymer is exposed to further hydrophobic modification.…”

A scanning electron microscope study of the surface structure of mineral pigments, latices and thickeners used for paper coating on non-absorbent substrates

“…In contrast to CMC, EHEC adsorbs to latex particles [35]. The strong interactions between EHEC and other components of the coating colour indicate that the presence of EHEC will strongly influence the structure of the coating.…”