We employ a fluorescence bilayer
method to directly measure the
glass transition temperature (T
g) of the
irreversibly adsorbed layer of polystyrene (PS) buried in bulk films
as a function of adsorption time, t
ads. This bilayer geometry allows for the examination of interfacial
effects on T
g of the adsorbed nanolayer.
In the presence of a free surface, we observe a substantial reduction
in T
g from bulk that lessens with t
ads as a result of increased chain adsorption
at the substrate. Submerging the adsorbed layer and effectively removing
the free surface results in a suppression of the T
g deviation at early t
ads,
suggesting chain adsorption dictates T
g at long t
ads. Annealing in the bilayer
geometry promotes recovery of bulk T
g on
a time scale reflecting the degree of adsorption. Our data are quantitatively
rationalized via the free volume holes diffusion model, which explains
adsorbed nanolayer T
g in terms of the
diffusion of free volume pockets toward interfacial sinks.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.