Dense polystyrene (PS) brushes were synthesized on silica wafers via a "grafting from" technique using activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP). Spectroscopic ellipsometry and fluorescence spectroscopy were used to investigate the effect of nanoscale confinement on the glass transition temperature (T-g) and its distribution in dense PS brushes and bilayer constructs of brushes and freely deposited PS films. Single-layer PS brushes exhibit an overall average T-g that is nearly invariant with thickness down toll nm, with T-g values of the dense brushes differing by no more than 2 degrees C from those of bulk PS of the same molecular weight as that of the brush. These results differ greatly from those obtained with freely deposited PS films that show major T-g reductions with confinement Distributions of T(g)s were also studied by fluorescence in dense, similar to 70-nm-thick PS brushes. Relative to T-g,T-buik, chain segments within 10 nm of the substrate exhibit a similar to 36 degrees C increase in T-g while segments within 5 nm of the free surface exhibit a 14 C decrease in T-g. Fluorescence was also used to characterize the tunability of T-g within a single layer of bilayer constructs. As brush thickness increases from 13 to 94 nm, the T-g of a 15-nm-thick PS overlayer film decreases from 100 degrees C to 87 degrees C; in contrast, as the overlayer PS film thickness increases from 0 to 101 nm, the T-g of an 11-nm-thick underlayer PS brush increases from 98 degrees C to 126 degrees C. These results are compared with the few previous experimental reports of T-g-confinement effects of densely grafted PS brushes and bilayer constructs of brushes and films. (C) 2015 Elsevier Ltd. All rights reserved.