Playing with Polydispersity: A Systematic Study of the Rheological Behaviour of Colloidal Suspensions as a Function of Polydispersity.

Polydispersity can be described at the ‘dark horse’ of colloidal synthesis. While it is often used to supress crystallisation in the study of glasses the synthesis of particles of a target polydispersity remains an experimental challenge. Therefore, studies of polydisperse suspensions generally focus on a single polydisperse system (Heckendorf 2017) or creating binary systems by mixing multiple mono-disperse populations (Lynch 2008, Vasisht 2016). Consequently, there is a scarcity of studies on how the properties of colloidal suspensions change as a function of polydispersity.

In this talk we present a novel synthesis pathway for creating colloidal microspheres with a target polydispersity, from 5-30%, in a controlled and repeatable manner. Crucially, these particles can be imaged in 3D using confocal microscopy uniquely allowing the resolution of individual particle size in both a dilute and concentrated suspension.

Utilising our confocal rheology platform we systematically study the impact of polydispersity on the rheological behaviour of dense colloidal suspensions with simultaneous direct visualisation of the microstructure. This approach allows us to reveal a surprising increase in elasticity with increasing polydispersity.