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Particle Dynamics in Colloid-Polymer Mixtures with Different Polymer Architectures.

ABSTRACT: Nonadsorbing polymers are widely used as thickening agents for colloids. A quantitative description of the structure and dynamics of such colloid-polymer mixtures is crucial to reveal the mechanisms accounting for the desired mechanical properties. We use confocal microscopy to study colloids with three types of commonly used polymers with different architectures: linear, subgranular cross-linked, and branched microgels. All three thickeners give rise to heterogeneous colloidal dynamics, characterized by non-Gaussian displacement distributions. However, while the ensemble-averaged particle dynamics in these materials are very similar, the underlying individual particle dynamics are not. Linear polymers give rise to depletion attraction and the formation of colloidal gels, in which the majority of particles are immobilized, while a few weakly bound particles have much higher mobility. By contrast, the branched and cross-linked polymers thicken the continuous phase of the colloid, squeezing the particles into dense pockets, where the mobility is reduced and requires more cooperative rearrangements.

SUBMITTER: Wu Q

PROVIDER: S-EPMC7503516 | biostudies-literature | 2020 Sep

REPOSITORIES: biostudies-literature

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Particle Dynamics in Colloid-Polymer Mixtures with Different Polymer Architectures.

Wu Qimeng Q Higler Ruben R Kodger Thomas E TE van der Gucht Jasper J

ACS applied materials & interfaces 20200902 37

Nonadsorbing polymers are widely used as thickening agents for colloids. A quantitative description of the structure and dynamics of such colloid-polymer mixtures is crucial to reveal the mechanisms accounting for the desired mechanical properties. We use confocal microscopy to study colloids with three types of commonly used polymers with different architectures: linear, subgranular cross-linked, and branched microgels. All three thickeners give rise to heterogeneous colloidal dynamics, charact ...[more]

PMID: 32812728

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Project description:ObjectivesThis study was aimed at the investigation of the supramolecular systems based on cationic surfactants bearing cyclic head groups (imidazolium and pyrrolidinium) and polyanions (polyacrylic acid (PAA) and human serum albumin (HSA)), and factors governing their structural behavior to create functional nanosystems with controlled properties. Research hypothesis. Mixed PE-surfactant complexes based on oppositely charged species are characterized by multifactor behavior strongly affected by the nature of both components. It was expected that the transition from a single surfactant solution to an admixture with PE might provide synergetic effects on structural characteristics and functional activity. To test this assumption, the concentration thresholds of aggregation, dimensional and charge characteristics, and solubilization capacity of amphiphiles in the presence of PEs have been determined by tensiometry, fluorescence and UV-visible spectroscopy, and dynamic and electrophoretic light scattering.ResultsThe formation of mixed surfactant-PAA aggregates with a hydrodynamic diameter of 100-180 nm has been shown. Polyanion additives led to a decrease in the critical micelle concentration of surfactants by two orders of magnitude (from 1 mM to 0.01 mM). A gradual increase in the zeta potential of HAS-surfactant systems from negative to positive value indicates that the electrostatic mechanism contributes to the binding of components. Additionally, 3D and conventional fluorescence spectroscopy showed that imidazolium surfactant had little effect on HSA conformation, and component binding occurs due to hydrogen bonding and Van der Waals interactions through the tryptophan amino acid residue of the protein. Surfactant-polyanion nanostructures improve the solubility of lipophilic medicines such as Warfarin, Amphotericin B, and Meloxicam.PerspectivesSurfactant-PE composition demonstrated beneficial solubilization activity and can be recommended for the construction of nanocontainers for hydrophobic drugs, with their efficacy tuned by the variation in surfactant head group and the nature of polyanions.

Dataset Information

Particle Dynamics in Colloid-Polymer Mixtures with Different Polymer Architectures.

Publications

Particle Dynamics in Colloid-Polymer Mixtures with Different Polymer Architectures.

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