Details of Grant 

EPSRC Reference:	EP/J02113X/1
Title:	Dynamic arrest and non-equilibrium behaviour in suspensions of deformable colloids
Principal Investigator:	Mattsson, Dr K
Other Investigators:
Researcher Co-Investigators:
Project Partners:
Department:	Physics and Astronomy
Organisation:	University of Leeds
Scheme:	First Grant - Revised 2009
Starts:	29 November 2012	Ends:	28 May 2014	Value (£):	100,410
EPSRC Research Topic Classifications:	Complex fluids & soft solids
EPSRC Industrial Sector Classifications:	No relevance to Underpinning Sectors
Related Grants:
Panel History:	Panel Date Panel Name Outcome 18 Apr 2012 EPSRC Physical Sciences Physics - April Announced
Summary on Grant Application Form
The molecules of a liquid move easily and a snap-shot of the molecular arrangements reveal complete disorder. As a liquid is cooled, it often undergoes crystallization, where the molecules arrange into an ordered pattern. The most common example is water turning into ice. However, such crystallization can be avoided by cooling at a fast rate. The liquid molecules then move slower and slower upon cooling and if the cooling rate is high enough there is not enough time to rearrange into an ordered pattern before all long-range motions come to a halt; thus, the structure remains disordered and liquid-like but the material is hard - the resulting solid is called a glass. Glassy materials are important in a wide range of man-made materials and applications including battery electrolytes and electrodes, solar cells, pharmaceuticals and most plastics. Neither the microscopic mechanisms involved in glass-formation nor the behaviour of the glassy state are well understood; this is remarkable since humans have been producing glass for thousands of years and glasses have been naturally formed by geological processes for millions of years. Thus, reaching an understanding of glasses and their formation is a key unsolved problem in both fundamental science and technology. Remarkably, an analogy can be drawn between and the molecules (size: 0.1-10 nm) of molecular glass-formers and the behaviour of particles (size: 0.1-10 microns) suspended in a liquid, so called colloids. For colloids, glass-formation is controlled by the concentration of particles within a certain volume; for low particle concentrations the system is a liquid but as the concentration is increased the system gets crowded, which leads to the formation of a glass. Practical examples include paints, emulsions, lubricants and thickeners. The advantage of using colloids as a model system to study glass-formation is the large particle size, which means that the colloid motions can be studied using light as a probe, together with the great control of properties such as colloid size, elasticity and inter-particle interactions. In this work we will use a versatile colloidal model system consisting of gel particles swollen in a solvent, so called microgels. In addition to their role as model systems, such microgel suspensions are important in applications including biosensing and medical diagnostics, chemical separation technologies, oil recovery, pharmaceutical delivery, and switchable materials. We will synthesize microgel particles with varying mechanical properties, by controlling the cross-linking of the particle gels. Each microgel batch will be characterized with regards to particle size, gel structure and mechanical properties. We will then study how these microgel suspensions form glasses as the particles crowd the volume upon concentration. Both the arrangement and the motions of the microgel particles will be studied as the glassy state is approached, using light scattering and rheology techniques. Light scattering studies yield information about the individual microgel structure, the microgel particle arrangements and the microgel motions over a wide range of time-scales (10 ns-1000 s). With rheology, the response of the material to a mechanical disturbance is investigated. Specific aims of the study are to (i) find the relationship between single microgel properties and the corresponding suspension arrangements and motions as the glassy state is approached (ii) determine which types of microgel motions are relevant to the glass formation process and how these motions are inter-related (iii) investigate how an applied shear affects and eventually 'melts' a microgel glass. This work addresses questions that are key to an understanding of glassy materials in general. By systematic studies of an excellent model system, we aim to form a benchmark for future glass-transition work.
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