Nanorheology of poly - and monodispersed polymer brushes under oscillatory flow as models of epithelial cancerous and healthy cell brushes

Synergy between surfactants' stiffness and concentration on their self-assembly into reverse micelles as water droplet carriers in nonpolar solvents

A study of the self-assembly process into reverse micelles (RMs) of linear surfactants and monomeric aqueous solutes dissolved in nonpolar solvents, varying the concentration (cs) and the persistence length (Lp) of the surfactants is presented here. The influence of cs and Lp on the structural and dynamic properties of the aggregates is investigated through mesoscopic simulations carried out with the dissipative particle dynamics method. All simulations are performed at a fixed water/surfactant molecular ratio of 2:1, varying the surfactant concentration from c = 6 wt% up to c = 12 wt%, for increasing surfactants' rigidity from Lp = 0.73 nm up to Lp = 44.99 nm. It is found that there exists a collaborative interplay between cs and Lp that enhances the number of RMs assembled and their diffusion as carriers of water droplets. These results should be useful as guidelines to understand and improve processes where the RMs are implemented to carry aqueous solutes in nonpolar solvents.

The viscosity of polyelectrolyte solutions and its dependence on their persistence length, concentration and solvent quality

In this work, a comprehensive study of the influence on shear viscosity of polyelectrolyte concentration, persistence length, salt concentration and solvent quality is reported, using numerical simulations of confined solutions under stationary Poiseuille flow. Various scaling regimes for the viscosity are reproduced, both under good solvent and theta solvent conditions. The key role played by the electrostatic interactions in the viscosity is borne out when the ionic strength is varied. It is argued that these results are helpful for the understanding of viscosity scaling in entangled polyelectrolyte solutions for both rigid and flexible polyelectrolytes in different solvents, which is needed to perform intelligent design of new polyelectrolytes capable of fine tuning the viscosity in complex fluids.

Mechanical response of a surface of increasing hardness covered with a nonuniform polymer brush: a numerical simulation model

The compression force with indentation on a polymer brush with chains of unequal lengths is predicted with numerical simulations, as a function of increasing hardness of the grafting surface, finding that properties of the brush are distinguished from those of the surface and that its hardness propagates through the brush.

The contributions to the force on a deformable surface covered with polymer brushes can be accounted for separately.