Salt-Controlled Vertical Segregation of Mixed Polymer Brushes.

Publisher: MDPI Country of Publication: Switzerland NLM ID: 101092791 Publication Model: Electronic Cited Medium: Internet ISSN: 1422-0067 (Electronic) Linking ISSN: 14220067 NLM ISO Abbreviation: Int J Mol Sci Subsets: MEDLINE

Original Publication: Basel, Switzerland : MDPI, [2000-

Hydrophobic and Hydrophilic Interactions* ; Polymers*/chemistry ; Salts*/chemistry; Osmolar Concentration ; Solvents/chemistry ; Polyelectrolytes/chemistry ; Surface Properties ; Models, Chemical

Using the self-consistent field approach, we studied the salt-controlled vertical segregation of mixed polymer brushes immersed into a selective solvent. We considered brushes containing two types of chains: polyelectrolyte (charged) chains and neutral chains. The hydrophobicity of both types of chains is characterized by the Flory-Huggins parameters χC and χN, respectively. It was assumed that the hydrophobicity is varied only for the polyelectrolyte chains (χC), while other polymer chains in the brush remain hydrophilic (χN=0) and neutral. Thus, in our model, the solvent selectivity (χ=χC-χN) was varied, which can be controlled in a real experiment, for example, by changing the temperature. At low salt concentrations, the polyelectrolyte chains swell and occupy the surface of the mixed brush. At high salt concentrations, the hydrophobic polyelectrolyte chains collapse and give place to neutral chains on the surface. By changing the selectivity of the solvent and the ionic strength of the solution, the surface properties of such mixed brushes can be controlled. Based on the numerical simulations results, it is shown how the critical selectivity corresponding to the segregation transition in polyelectrolyte/neutral brushes depends on the ionic strength of the solution. It is shown that at the same ionic strength, the critical selectivity increases with an increasing degree of dissociation of charged groups, as well as with an increasing fraction of polyelectrolyte chains in the mixed brush. It has also been shown that at low ionic strengths, the critical selectivity of the solvent decreases with increasing grafting density, while at high ionic strengths, on the contrary, it increases. Within the framework of the mean field theory, a two-parameter model has been constructed that quantitatively describes these dependencies.

Keywords: height switch; mixed polymer brushes; phase segregation; strong polyelectrolyte

0 (Polymers)
0 (Salts)
0 (Solvents)
0 (Polyelectrolytes)

Date Created: 20241217 Date Completed: 20241217 Latest Revision: 20241217

20241217

10.3390/ijms252313175

39684885