Suppressed Tg-Confinement Effects in Thin Films of Comb and Branched Polystyrene Relative to Linear Polystyrene

The effects of nanoscale confinement on the glass transition temperature, Tg, of comb and branched polystyrene (PS) are compared to those of linear PS. Comb and branched PS are synthesized using alkoxyamine dynamic chemistry. Upon appropriate stimulus, this dynamic chemistry allows the comb and branched PS to revert to its linear components, thus allowing for direct comparison. Using thin films of PS on silica substrates, Tg reductions are characterized via ellipsometry measurements of both comb and branched PS films, with confinement effects being suppressed in non-linear PS compared to their linear components, respectively. The reduced magnitude of Tg reduction observed in confined comb and branched PS films may be attributed to the effect of chain architecture (on the underlying fragility-confinement effect) and possibly to polymer-substrate interaction. Direct comparison of fragility-confinement effects in thin films of comb and branched PS thin films is also being made to effects in thin films of linear PS.