pH-controlled breakup of fractal aggregates, microgels and gels formed by self-assembled amphiphilic triblock copolymers.

The degradation of (micro)gels and fractal aggregates based on self-assembled amphiphilic triblock copolymers has been investigated in water by confocal microscopy and light scattering respectively. The triblock copolymer consisted of a central hydrophilic poly(acrylic acid) (pAA) block and two hydrophobic end blocks that contained an equal amount of randomly distributed -butyl acrylate (BA) and AA units. These latter units helped at tempering the hydrophobic end blocks resulting in the control and the fine tuning of the dynamics of the self-assembled triblock through the pH.

Raman Tweezers for Small Microplastics and Nanoplastics Identification in Seawater.

Our understanding of the fate and distribution of micro- and nano- plastics in the marine environment is limited by the intrinsic difficulties of the techniques currently used for the detection, quantification, and chemical identification of small particles in liquid (light scattering, vibrational spectroscopies, and optical and electron microscopies). Here we introduce Raman Tweezers (RTs), namely optical tweezers combined with Raman spectroscopy, as an analytical tool for the study of micro- and nanoplastics in seawater. We show optical trapping and chemical identification of sub-20 μm plastics, down to the 50 nm range.

Specific effect of calcium ions on thermal gelation of aqueous micellar casein suspensions.

Aqueous suspensions of micellar casein (MC) gel when heated above a critical temperature that depends on the pH. The effect of adding CaCl and EDTA on thermal gelation was studied in order to assess the effect of increasing or decreasing the amount of bound Ca on the process. The effect of adding NaCl was investigated in order to distinguish the effect of Ca binding from the effect of screening of electrostatic interactions.

Inhibition and Promotion of Heat-Induced Gelation of Whey Proteins in the Presence of Calcium by Addition of Sodium Caseinate.

Heat-induced aggregation and gelation of aqueous solutions of whey protein isolate (WPI) in the presence of sodium caseinate (SC) and CaCl was studied at pH 6.6. The effect of adding SC (0-100 g/L) on the structure of the aggregates and the gels was investigated by light scattering and confocal laser scanning microscopy at different CaCl concentration ([CaCl] = 0-30 mM).

Relation between the gel structure and the mobility of tracers in globular protein gels.

Diffusion of fluorescent-labeled dextran with different molecular weights was investigated in β-lactoglobulin (β-lg) solutions and gels over a wide range of salt and protein concentrations at pH 7 by combining confocal laser scanning microscope (CLSM) with fluorescence recovery after photobleaching (FRAP). Effects of the protein concentration, the salt concentration and the tracer size were investigated in detail. Diffusion in turbid heterogeneous gels formed at 0.

Particles trapped at the droplet interface in water-in-water emulsions.

Water-in-water emulsions were formed by mixing incompatible aqueous solutions of dextran and poly(ethylene oxide) (PEO) in the presence of latex or protein particles. It was found that particles with a radius as small as 0.1 μm become trapped at the interface between the PEO- and dextran-rich phases with interfacial tensions down to 10(-6) N/m.

Particle diffusion in globular protein gels in relation to the gel structure.

Globular protein gels with a variety of structures were prepared by heating β-lactoglobulin solutions at different concentrations and different ionic strengths. The structure was analyzed in terms of the pair correlation function of the protein concentration, and the volume fraction of the gels was determined. A strong coarsening of the gel structure was observed upon increasing the NaCl concentration between 0.