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Unité de Formation et de Recherche de Chimie
UFR926

"How do polymers behave in small spaces ?" Mardi 11 juin 2019

Stuart W Prescott

 

(UNSW Chemical Engineering)

 

"How do polymers behave in small spaces?"

 

The solvent-mediated forces between macromolecular structures at surfaces are the essence of the physics of adhesion, steric stabilisation of colloids, tack in rubbers, biofouling, lubrication and many other problems in particle aggregation and coalescence. Colloidal systems are heavily dependent on these forces and the polymers that are adsorbed or grafted to particles can either enhance the stability of colloidal dispersions or promote aggregation.

 

We have combined a surface force type apparatus with neutron reflection to measure the structure of polymer brushes in confined geometries. Our system mimics the collision between two particles or surfaces, with the geometrical confinement leaving the polymer molecules trapped between the impinging interfaces. The polymers are highly perturbed by the confined geometry while the solvent is free to leave.

 

Contrary to expectations, we find that polymer brushes collapse under relatively small applied loads; steric stabilisation of colloids by polymers is substantially weaker than than imagined. We also find that the degree of interpenetration of polymers as the surfaces impinge can be tuned by using polymers that are responsive to pH.

 

About Stuart Prescott

Stuart’s research interests are in the relationships between the molecular structures that are found at interfaces and the control of properties at interfaces. He studies surfactant structures, adsorbed polymers and polymer brushes with the goals of tailoring colloidal stabilisation formulations and designing responsive surfaces. Stuart joined UNSW Chemical Engineering as a Senior Lecturer in 2013, following seven years at the University of Bristol. He held an EU Marie Curie individual fellowship to develop a neutron reflection sample environment for studying the effects of confinement on polymers and has also worked on the development of bench-top NMR instrumentation for use with colloidal systems. His PhD research (Uni Sydney, 2004) was with Prof RG Gilbert and Prof E Rizzardo, and demonstrated the first successful RAFT-mediated living polymerisation in an emulsion polymerisation reaction. Stuart collaborates widely, looking at the surface chemistry and colloidal aspects of wide ranging fields including touch perception, drug delivery and consumer products.

 

29/05/19

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