We are thankful to be welcome on these lands in friendship. The lands we are situated on are covered by the Williams Treaties and are the traditional territory of the Mississaugas, a branch of the greater Anishinaabeg Nation, including Algonquin, Ojibway, Odawa and Pottawatomi. These lands remain home to many Indigenous nations and peoples.

We acknowledge this land out of respect for the Indigenous nations who have cared for Turtle Island, also called North America, from before the arrival of settler peoples until this day. Most importantly, we acknowledge that the history of these lands has been tainted by poor treatment and a lack of friendship with the First Nations who call them home.

This history is something we are all affected by because we are all treaty people in Canada. We all have a shared history to reflect on, and each of us is affected by this history in different ways. Our past defines our present, but if we move forward as friends and allies, then it does not have to define our future.

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November 12, 2014

Speaker: Robert Wickham, Associate Professor, Department of Physics, University of Guelph

Title: Simulation of structure and dynamics in the disordered micelle regime of a diblock copolymer melt

Abstract: Diblock copolymers are long, chain-like molecules composed of two sub-chains, or blocks, of different chemical species. In a dense melt of diblock copolymers, there is competition between an effective repulsion that tends to separate unlike blocks and entropy, which tends to coil the chain. At low temperatures, a compromise between these two tendencies is reached and this results in microphase separation of the blocks into ordered domain structures at nanometer scales. This process is known as molecular self-assembly.

There has been a tremendous focus on the low-temperature ordered phases: for example, the body-centred cubic (bcc) arrangement of spherical polymeric aggregates called micelles. However, experiments reveal that the high-temperature disordered phase has a surprising amount of structure itself, with indications of localized, strongly segregated domains – a disordered liquid of micelles – existing as part of the disordered phase. This disordered micelle regime is challenging to study theoretically because one needs to go beyond the mean-field theories typically employed, which predict that the disordered phase is featureless, and include composition fluctuations in the model for a proper description of the structure.

In this talk, I will discuss large-scale, fluctuating, dynamical field-theoretic simulations we use to comprehensively characterize the structure and dynamics of the disordered micelle regime. Our simulations provide insight into how and when the disordered micelle liquid is formed; the nature of the micelles as polydisperse hard spheres; and the sluggish dynamics of the micelle liquid as it is cooled, which has implications for the kinetics of formation of the bcc ordered phase.