Multiscale Modelling of Colloid-Polymer Systems for Novel Vi scoelastic Materials

Lead Research Organisation: University of Birmingham
Department Name: School of Chemistry

Abstract

Context
Colloid-polymer systems, which offer the scope for tuning inter-particle interactions, are of interest for both fundamental science and formulation engineering. These systems, compared to hard-sphere colloids, display a more complex phase behaviour, and illustrate the importance of the kinetics of phase transitions in the presence of metastable states. Moreover, colloid-polymer systems find wide applications in cosmetic and personal care formulations, where the shelf life and rheology of the products are critical. Understanding the fundamentals of colloid-polymer systems thus holds the key to informed formulation of many consumer products. From these perspectives, the questions pertinent to the stability and mechanical properties of colloid-polymer systems are of particular relevance. Although computer simulation studies have become a useful means, complementary to theory and experiment, to address these questions, the length and time scales involved in the problem demand further methodological advances, especially in the context of investigating the rheology of these soft materials.
Aim and objectives
The aim of this PhD project is to develop a novel computational platform to further our capability of rationally designing colloidal-polymer systems, with tailored microstructure and rheology of industrial relevance, and forecasting their stability.
The major objectives of this project are to relate microstructure to viscoelastic response of these soft matter systems and to explore the prospects for designing soft materials with novel viscoelastic properties.
Novelty of the research methodology
To this end, the project will employ advanced simulation techniques and multiscale modelling to investigate the structure, dynamics and viscoelastic properties of these multicomponent systems. The dissipative particle dynamics (DPD) simulation technique has emerged as a useful mesoscale computational tool for investigating the rheology of particulate suspensions for the advantages it offers in the treatment of spatial and temporal scales involved in an explicit solvent description. The DPD simulation technique will underpin the novel computational platform that we aim to develop for multiscale modelling. The methodological development will seek parameterisation to allow representation of real systems. The applications of this computational platform will inform formulation of soft mat materials with novel viscoelastic properties.
Potential impact
The project will result in an enabling capability of designing soft materials with tailored microstructure and rheology, which will have strong implications for informed formulation of consumer products of industrial relevance.
The research programme will train the PhD student in the broad interdisciplinary field of soft matter and the student will develop expertise in state-of-the-art computational methods, underpinned by the theoretical framework of statistical mechanics, to study soft matter in general, and specifically colloid-polymer systems. The trained individual will be of immense value also to meet the demand of skilled researchers in the area of modelling and computation at industries such as Procter & Gamble, Unilever, BP, Shell and many others, where colloid science has a strong base.
Alignment to EPSRC's strategies and research areas
The present project is in the research area of complex fluids and rheology, which is crucial for the UK's formulation capability. This project falls within the remit of the EPSRC's theme, manufacturing the future, and supports recent initiatives for informed formulation. In fact, formulation is one of the 22 priorities identified in the Innovate UK High Value Manufacturing strategy.

Publications

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Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/N509590/1 01/10/2016 30/09/2021
1802786 Studentship EP/N509590/1 01/10/2016 30/09/2019 Christopher Avins Avins
 
Description Understanding the rheology of colloidal dispersions is of significant importance for both fundamental interest and practical applications. The focus of colloid rheology has largely been on dispersions of spherical colloidal particles, where the inter-particle interactions which govern the microstructure, are isotropic. Since the turn of the 21st century, advances in particle synthesis have made available a variety of colloidal particles that involve anisotropic inter-particle interactions due to shape and/or surface chemistry. Colloidal dumbbells offer an attractive model system to advance our understanding of how the microstructure governs colloidal rheology beyond the well-studied isotropic limit. In this context, we have investigated systems of symmetric as well as asymmetric colloidal dumbbells, where the interparticle interactions can be tuned with polymers, including DNA, a special kind of polymers that can offer selectivity in the interactions. Our key findings so far are as follows:
(1) the aspect ratio, i.e. the length-to-breadth ratio which governs the shape, critically influences the shear viscosity of the colloidal dispersion;
(2) the shape and surface chemistry can be exploited to form clusters in a controlled way to manipulate the colloidal rheology.

This is an ongoing project, upon completion of which the findings can be described in more detail. We envisage that our key findings will help inform formulation of consumer products by design in the long run.
Exploitation Route Although the award is finished, I am currently self-funding myself to drive the project forward in order to be able to write my PhD thesis within next six months. This additional time window will enable me complete certain strands of the project and develop the software to a level so that it can be used by others to create research impact.
Sectors Chemicals

 
Title Brownian Dynamics for colloidal dumbbell particles 
Description We have developed a Brownian Dynamics code to simulate colloidal dumbbell particles in the absence or presence of an external shear force. In addition, a dissipative particle dynamics code for simulating colloid-polymer mixture is being developed. Brownian Dynamics is a useful tool for studying rheology as the Brownian motion imparted on the colloids from the solvent is taken into account, giving a better approximation than a Molecular Dynamics approach. As the solvent is modelled implicitly BD is also a more efficient model in terms of computational time. 
Type Of Material Improvements to research infrastructure 
Year Produced 2019 
Provided To Others? No  
Impact We have outlined some notable impacts in the Key Findings section of this submission.