Effect of methanol on surfactants and surfactant–PEO mixtures

Abstract

Methanol–water system possesses unusual interactions, which may affect surfactant self‐assembly. The main objective of this study was to investigate the interactions and aggregation behavior of ionic surfactants sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB) and their equimolar catanionic binary mixtures (CAM) and their ternary mixtures with poly(ethylene oxide) (PEO) in aqueous solutions containing different volume percentages of methanol. Conductometry, surface tensiometry, and dynamic light scattering were employed for this purpose. The aggregation in all the systems showed methanol‐dependent patterns. The maximum shifts observed in the critical aggregation concentrations were 5.5, 2.7, 6.3, 4.1, and 4.4 mM, respectively, for SDS, CTAB, CAM, SDS/PEO, and CTAB/PEO systems for variation in MeOH from 5% to 30% v/v. The change in dielectric of the media and chaotropic nature of methanol was responsible for alteration in self‐assembly. The nature of surfactant especially and head group hydrophobicity also played a significant role in the process. The maximum change in area per molecule (i.e., ~4 nm2) occurred for CTAB/PEO system. The aggregation was delayed in surfactant solutions; however, the presence of polymer induced aggregation due to favorable polymer–surfactant interactions involving the surfactant adsorption onto polymer chains and formation of mixed aggregates. The hydrodynamic radii for CTAB/PEO systems, which were nearly 10 times greater than those recorded for SDS/PEO, showed the transition of system to nonspherical aggregated states. In short, the presence of methanol retarded the aggregation in surfactant and surfactant–polymer systems.

Troubleshooting the influence of trace chemical impurities on nanoparticle growth kinetics via electrochemical measurements

“…This can increase the size of micelles and cause more disorder and/or patterns of interdigitation in hydrocarbon tails. 29–41 Solvent molecules in even low concentrations can also cause chaotropic effects that can affect the behavior of micelles and bilayers, and presumably also of other solutes. 29,33…”

“…29–41 Solvent molecules in even low concentrations can also cause chaotropic effects that can affect the behavior of micelles and bilayers, and presumably also of other solutes. 29,33…”

“…This can increase the size of micelles and cause more disorder and/or patterns of interdigitation in hydrocarbon tails. [29][30][31][32][33][34][35][36][37][38][39][40][41] Solvent molecules in even low concentrations can also cause chaotropic effects that can affect the behavior of micelles and bilayers, and presumably also of other solutes. 29,33 Generalizability of the acetone and iodide adjustment scheme to all batches of BioUltra CTAB was achieved by ovendrying the as-received BioUltra B powder at 80 to 100 °C for 24 hours.…”

“…[29][30][31][32][33][34][35][36][37][38][39][40][41] Solvent molecules in even low concentrations can also cause chaotropic effects that can affect the behavior of micelles and bilayers, and presumably also of other solutes. 29,33 Generalizability of the acetone and iodide adjustment scheme to all batches of BioUltra CTAB was achieved by ovendrying the as-received BioUltra B powder at 80 to 100 °C for 24 hours. Modification of a dried BioUltra B-based growth solution with 0.68 µM NaI and between 190 µL and 270 µL of acetone (0.26 M to 0.36 M in the growth solution) was sufficient to produce THH under otherwise standard conditions (Fig.…”