Title: Stimuli-responsive and nanostructured polymer films for modulating adhesion and friction between surfaces: fabrications, applications and limitations
Speaker: Prof. Suzanne Giasson, Universite de Montreal|
Venue: Room 318, Building B12, University Town Campus
Time: January 7, Tuesday, 10：00
Suzanne Giasson is a professor of physical-chemistry and material sciences at Universite de Montreal (Quebec, Canada). Prof. Giasson’s current research program is on the development and investigation of responsive micro/nano-structured surfaces and coatings whose physical properties and surface chemistry can be tuned reversibly. The hierarchical structures are obtained by approaches using surface chemistry, polymer sciences and self-assembly. Such responsive nanostructured materials enable significant advances in biomedical surface engineering and microfluidics. Her research efforts have led to the completion of several papers in refereed journals (Nature, Soft Matter, Macromolecules, Langmuir, J. of Physical-Chemistry, J. of Pharmaceutical Science, J. of Rheology, J. Physics: Condensed Matter and others). She reported the first results on measurement of interactions and friction between charged polymer brushes (Nature 2003) cementing one her main research axis that is nanotribology. In addition, she also developed reliable approaches to covalently grafted nanostructured polymer layers on silica-based materials. Her novel findings have made a decisive impact on subsequent studies in these areas. Her research activities have also been reported beyond the scientific community. She has been invited to participate in a range of different informal activities, including radio and TV programs and magazine interviews. More particularly, the quality and impact of her pioneer work on lubrication by charged polymer brushes research activities have been recognized by a team composed of scientists and journalists, as a Top Ten 2003 Discovery for Quebec Science magazi.
A number of experimental studies have shown that supported thin polymer films can be efficiently used to modulate surface properties including adhesion and friction. Such polymer coatings have properties and responsiveness that are contingent on the chemical composition, size and shape of structure, elasticity. However, they are generally suffering from major shortcomings such as lack of responsiveness selectivity and reversibility, poor environmental stability and limited understanding of the structure–function relationship, which are all critical to design reliable rules for building responsive surfaces in a selective way. Experimental surface forces studies of different classes of solvated polymer-bearing surfaces carried out using the surface forces apparatus and similar molecular techniques will be presented in order to elucidate the responsiveness mechanism and the structure–property relationship between different polymer-coated surfaces in aqueous media. Even though conclusive understanding is still hampered by the difficulty of systematically controlling the polymer grafting density and conformation under shear and compression, the studies suggest that the effective adhesion and lubrication mechanisms involve the facility with which macromolecules under compression remain hydrated and hold a significant amount of water at the surfaces to be lubricated. This could be optimized by immobilizing different microgels on substrates for which the friction coefficient decreased exponentially with an increasing the swelling ratio regardless of the size, surface coverage, and degree of ionization of the particles. In addition, the robustly attached microgel particles were able to sustain high pressure (up to 200 atm) without significant surface damage.
Announced by the School of Materials Science and Engineering