Sommaire:

The paper presents systematic study on stability of the ATPS composed of mixtures of incompatible polymers (polyethylene glycol and dextran), stabilized by nanogel particles of bovine milk protein (β-lactoglobulin –BLG), further referred as (PEG(Mw)-in-DEX(Mw))BLG, where Mw is molecular mass of polymer used in our studies. The Mw of PEG was changed in the range 10-20kDa, while DEX in the range 20-75kDa. Four different blend solutions with different Mw of each polymer were prepared. Firstly, a comprehensive characterization of the investigated systems was carried out, including density as well as viscosity measurements, before and after mixing. In addition, in situ imaging was conducted using confocal microscopy, and interfacial tensions were examined using SDT (Spinning Drop Tensiometer).
After analyzing stability of several systems , a new relationship related to the molecular weight of polymers in terms of ATPS stability was revealed. It was found that with increasing the difference between molecular weight of polymer forming the continuous and dispersed phases, the stability of the protein-stabilized systems was increasing, as well. This effect resulting from changes in polymer molecular weights in presence of BLG nanogels particles led to spectacular extension of the emulsion stability.
Furthermore, it was found that the nanogel particles size, adjusted by proper synthesis conditions (mainly pH of native BLG solution before synthesis), strongly affects the ATPS stability which reaches its optimum for the BLG particles diameter ranging between 50 and 80 nm (pH of BLG native solution 5,9-6,1) (Fig. 1., BLG concentration equal to 0,105 % w/w). It was found, moreover that too large and too small nanoparticles did not stabilize the system effectively, what should be associated to BLG size-dependent ability of accumulation inside the interfacial region (between PEG and DEX rich phases).

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