Development and implementation of coarse-grained force fields for an accurate description of the thermodynamic and morphological properties of surfactant solutions using molecular dynamics

Abstract

The world is constantly striving for increased innovation and efficiency. This may be for financial or idealistic reasons, from the capitalist standard in attempting to increase profit to arguably more fulfilling endeavors aiming to make a difference environmentally or socioeconomically. While these issues are often associated with finance or politics, it has never been more true that science is the silent engine that ultimately underpins advancement.

For example, chemical industries are under increased scrutiny due to their environmental impacts. Transition to greener, more sustainable components is therefore critical, but how can this be achieved quickly while maintaining a high standard? One particularly lucrative area has been the integration of molecular modelling in product development, which allows easy access to properties and data that can provide potential candidates for new formulations without wasting valuable materials. High quality, robust models also allow for intricate studies of internal structural properties not easily accessible through experiment, promoting further understanding and potential innovation.

Within this thesis, it is hoped that the creation and utilisation of several molecular models of surfactants provides a glance of the capabilities of molecular modelling. Surfactants are amphiphilic molecules utilised in products ranging from detergents to drug discovery. With their exponential growth in usage, it has become increasingly important to understand their lucrative behaviours; particularly as 'designer surfactants' promise bespoke applications. Firstly, the development of a coarse grained polyoxyethylene (POE) surfactant model utilising the SAFT-$\gamma$ Mie equation of state for use within molecular dynamics (MD) simulation is presented. This is then used to investigate morphology and other systematic properties - showing impressive agreement to experimental findings. Lastly, a separate variant of coarse grained modelling, dissipative-particle dynamics (DPD), is used to investigate ternary mixtures of ionic surfactant systems. Important properties are extracted and efficient workflows established to allow easy comparison between systems.