Solvatochromic and Acid–Base Molecular Probes in Surfactant Micelles: Comparison of Molecular Dynamics Simulation with the Experiment (a Review)

This article summarizes a series of seventeen publications by the authors devoted to molecular dynamics modeling various indicator dyes (molecular probes) enclosed in surfactant micelles. These serve as generally recognized tools for studying types organized solutions, among which micelles water are simplest and most explored. The procedure involves altogether 50 95 molecules, 16 28 thousand single dye molecule. presentation simulation results was preceded brief review state experimental studies. consists three parts. First, despite numerous literature data itself, we decided revisit this issue. structure hydration surface surfactants, first all sodium n-dodecylsulfate, SDS, cetyltrimethylammonium bromide, CTAB, were studied. values electrical potential, Ψ, estimated functions ionic strength distance from surface. decrease Ψ value with is gradual. Attempts consider both DS− CTA+ without counterions result decay into two smaller aggregates. Obviously, hydrophobic interaction (association) hydrocarbon tails balances repulsion charged headgroups these small “bare” second part study seven pyridinium N-phenolates, known Reichardt’s dyes, powerful solvatochromic indicators now used examining colloidal systems. localization orientation zwitterionic (colorless) cationic forms consistent intuitive ideas about hydrophobicity substituents. Hydration has been quantitatively described molecule whole oxygen atom. A number markers, including visible absorption spectra enable assuming better micellar SDS than that CTAB. However, our show it more correct speak pronounced hydrogen-bonding ability molecules anionic compared CTAB ones. Finally, set acid–base firmly fixed pseudophase studied dynamics. They instruments estimating electrostatic potentials related aggregates Ψ= 2.303RTF−1 (pKai − pKaapp), where pKai pKaapp indices so-called intrinsic apparent dissociation constants. In case, addition location, orientation, hydration, differences between constants estimated. Only semi-quantitative agreement obtained. given solutions do much agree data. Accordingly, micelles, determined using nonionic pKai, reproduced reasonable accuracy corresponding indicator. following data, scatter obtained different observed. problem may be subject further research.