# Investigating molecular mechanism for the stability of ternary systems containing cetrimide, fatty alcohol and water by using computer simulation

## TL;DR

This study uses atomistic computer simulations to explore the molecular stability mechanisms of ternary systems containing cetrimide, fatty alcohols, and water, relevant for pharmaceutical creams, confirming experimental hypotheses about chain length mismatch effects.

## Contribution

It provides molecular-level insights into the stability of mixed fatty alcohol systems, supporting the role of chain length mismatch and configurational entropy in stability.

## Key findings

- Mixed alcohol systems are more stable than pure ones.
- Shorter alcohol molecules exhibit increased stiffness and higher order parameters.
- Simulated molecular structures agree well with experimental data.

## Abstract

Computer simulations using atomistic model are carried out to investigate the stability of ternary systems of pure or mixed fatty alcohols, cetrimide, and water. These semi$-$solid oil-in-water systems are used as the main component of pharmaceutical creams. Experiments show that the mixed alcohol systems are more stable than pure ones. The current experimental hypothesis is that this is the result of the length mismatch of the alkyl chains. This leads to higher configurational entropy of the chain tip of the longer alcohol molecules. Our simulation results support this hypothesis. The results also show that the shorter alcohol molecules become stiffer with higher values of the deuterium order parameters and smaller area per molecule. The magnitude in fluctuations in the area per molecule also increases in mixed systems, indicating a higher configurational entropy. Analysis of the molecular structure of simulated systems also shows good agreements with experimental data.