The modulus and Tg of a series of PS samples with varying architecture are examined in thin films as a function of thickness. The bulk-like, thick film Tg is independent of polymer architecture: linear, comb, centipede and 4 armed star PS. However for ultrathin (< 40 nm) films, the Tg becomes dependent upon polymer branching. Relative to linear PS, there is a further reduction in Tg for the thinnest films for the centipede PS, while Tg of both comb and star PS is less impacted as the film thickness decreases. In order to better understand this Tg behavior, the modulus for these PS architectures is also examined as a function of film thickness. The modulus exhibited a similar dependence on architecture with the modulus of the comb PS independent of film thickness. These dependencies on the architecture are attributed to variations in packing efficiency and interchain entanglements with branching.
Citation: Journal of Polymer Science Part B-Polymer Physics
Pub Type: Journals
glass transition, modulus, polymers, thin films, confinement, wrinkling, branching, architecture