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BEGIN:VEVENT
DTSTAMP:20261020T082747Z
LAST-MODIFIED:20160912T162832Z
DTSTART:20160927T180000Z
DTEND:20160927T190000Z
UID:event1663@bu.edu
URL:http://physics.bu.edu/internal/events/show/1663
SUMMARY:Dynamic Studies of Nano-Confined Polymer Thin Films
DESCRIPTION:Featuring Kun Geng\n\nPart of the Departmental Seminars.\n\nDis
	sertation Committee: Ophelia K.C. Tsui\, Tulika Bose\, Shyamsunder Erramill
	i\, Karl Ludwig\, Eugene Stanley \nAbstract:\nPrevious research found that 
	polymer thin films with thickness in the range of ~1−100 nm often exhibit
	 physical properties different from the bulk. Understanding the physical or
	igins of the deviations from bulk-like properties in polymer films under na
	noconfinement is of interest for both fundamental research and industrial a
	pplications. In this talk\, I will discuss how nanoconfinement influences s
	everal dynamic properties of polymer thin films\, including the glass trans
	ition temperature (Tg)\, effective viscosity (eff) and self-diffusion co
	efficient (D). First\, I will discuss the results obtained from an experime
	nt where I\, in collaboration with Ellison’s group in UT Austin\, studied
	 the Tg\, D and ηeff of poly(isobutyl methacrylate) films supported by sil
	ica (PiBMA/SiOx). Both the Tg and D were found to be independent of h0\, bu
	t eff decreased with decreasing h0. Since both D and ηeff describe tran
	sport phenomena known to depend on the local friction coefficient or equiva
	lently the local viscosity\, it is then questionable why D and ηeff displa
	yed seemingly inconsistent h0 dependences. We envisage the different h0 dep
	endencies to be caused by Tg\, D and ηeff being different functions of the
	 local Tg’s (Tg\,i) or viscosities (i)\, which vary with the film dept
	h. By assuming a three-layer model\, we were able to account for the experi
	mental data and resolve the inconsistency. By extending the same ideas to t
	he analogous data of polystyrene films\, we found a resolution to the long-
	standing inconsistency regarding the effects of confinement on the dynamics
	 of polymer films.\n\n![Kun](/resources/event-image/1663/e9739f1_small)
LOCATION:PRB 261\, 3 Cummington Mall\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
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