BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//RLASKEY//CALENDEROUS//EN
CALSCALE:GREGORIAN
METHOD:PUBLISH
BEGIN:VEVENT
DTSTAMP:20260816T131021Z
LAST-MODIFIED:20161114T154830Z
DTSTART:20161208T193000Z
DTEND:20161208T203000Z
UID:event1683@bu.edu
URL:http://physics.bu.edu/internal/events/show/1683
SUMMARY:Dynamic Studies of Nano-Confined Polymer Thin Films
DESCRIPTION:Featuring Kun Geng\n\nPart of the PhD Final Oral Exams.\n\nDiss
	ertation Committee: Ophelia K.C. Tsui\, Robert Carey\, Shyam Erramilli\, Ka
	rl Ludwig\, H.E. Stanley\n\nAbstract:\n\nPrevious research found that polym
	er thin films with thickness in the range of ~1−100 nm often exhibit phys
	ical properties different from the bulk counterpart. In order to make the b
	est use of polymer thin films in applications\, it is important to understa
	nd the physical origins of these deviations. In this talk\, I will investig
	ate how different factors influence dynamic properties of polymer thin film
	s upon nanoconfinement\, including the glass transition temperature (Tg)\, 
	effective viscosity (Eta) and self-diffusion coefficient (D). We simultaneo
	usly studied the effects of confinement on the Tg\, D and Eta of poly(isobu
	tyl methacrylate) films supported by silica (PiBMA/SiOx). Both the Tg and D
	 were found to be independent of film thickness (h0)\, but Eta was decrease
	d with decreasing h0. Since both D and Eta describe transport phenomena in 
	the films and are known to depend on the same sort of local dynamic propert
	ies\, it is then a question why D and Eta displayed seemingly inconsistent 
	h0 dependences. We envisage the different h0 dependencies to be caused by T
	g\, D and Eta being different functions of the local Tg’s (Tg\,i) or visc
	osities\, which vary with the film depth. By assuming a three-layer model\,
	 we were able to account for the experimental data and resolve this inconsi
	stency. By extending these ideas to the analogous data of polystyrene films
	 supported by silica\, we have found a resolution for the long-standing inc
	onsistency regarding the effects of confinement on the dynamics of polymer 
	films.\n\n\n![Kun](/resources/event-image/1683/51b27dc_original)
LOCATION:PRB 261\, 3 Cummington Mall\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
END:VCALENDAR