Microstructure design of CTAC:FA and BTAC:FA lamellar gels for optimized rheological performance utilizing automated formulation platform

Predicting surfactant phase behavior with a molecularly informed field theory

HYPOTHESIS

The computational study of surfactants and self-assembly is challenging because 1) models need to reflect chemistry-specific interactions, and 2) self-assembled structures are difficult to equilibrate with conventional molecular dynamics. We propose to overcome these challenges with a multiscale simulation approach where relative entropy minimization transfers chemically-detailed information from all-atom (AA) simulations to coarse-grained (CG) models that can be simulated using field-theoretic methods. Field-theoretic simulations are not limited by intrinsic physical time scales like diffusion and allow for rigorous equilibration via free energy minimization. This approach should enable the study of properties that are difficult to obtain by particle-based simulations.

SIMULATION WORK

We apply this workflow to sodium dodecylsulfate. To ensure chemical fidelity we present an AA force field calibrated against interfacial tension experiments. We generate CG models from AA simulation trajectories and show that particle-based and field-theoretic simulations of the CG model reproduce AA simulations and experimental measurements.

FINDINGS

The workflow captures the complex balance of interactions in a multicomponent system ultimately described by an atomistic model. The resulting CG models can study complex 3D phases like double or alternating gyroids, and reproduce salt effects on properties like aggregation number and shape transitions.

Impact of Processing Conditions on Rheology, Tribology and Wet Lubrication Performance of a Novel Amino Lipid Hair Conditioner

The objective of this work was to carry out a comprehensive evaluation of the performance of a novel cationic amino lipid surfactant, Brassicyl Valinate Esylate (BVE), in contrast to conventional alkyl quaternary ammonium surfactants (quats), through a study of the effects of process mixing speed on its overall rheological, tribological and wet lubrication performance in comparison to BTAC and CTAC, two cationic surfactants widely used in cosmetics. The major cosmetic application of cationic surfactants is in the preparation of hair conditioners. Hence, this analysis was done firstly by conducting tensile combing tests to evaluate reduction in wet lubrication which translates to conditioning performance. The combing results serve as a testing metric that adequately corresponds to consumer perception of conditioned hair. To correlate this technically, yield stress measurements were conducted to establish rheologic profiles of the conditioner formulations, and in vitro tribological testing of the emulsion systems between two steel surfaces were done to technically simulate the spreading and rubbing of conditioner on the hair. The effect of processing conditions on the formulations was then evaluated. BVE was found to be an effective conditioning surfactant suitable as an eco-friendly replacement for BTAC and CTAC in hair conditioner formulations. The results showed that higher shear mixing rates during formulation lead to poorer performance effects evident through decreased yield stress values, lower percentage reduction in combing force and a higher coefficient of friction.