Combined effects of polymer/substrate interaction and chain adsorption on the <i>T</i> g-confinement effect of supported thin polystyrene films
Abstract
The thickness dependence of the glass transition temperature (i.e., the Tg-confinement effect) and its molecular weight (Mw) dependence in polystyrene (PS) thin films supported on attractive substrates are systematically investigated as a function of annealing time at 423 K. It is demonstrated that the shift in Tg (ΔTg= Tgfilm − Tgbulk) exhibits a consistent linear dependence on the degree of adsorption (hads/hadseq) across PS films with different Mw on a given substrate, described by ΔTg = khads/hadseq + b. The slope k is found to be independent of the substrate, whereas the intercept b increases with the increasing polymer/substrate interactions due to additional losses in interfacial free volume arising from more densely packed adsorbed conformations. In addition, the dependence of the Tg-confinement effect on Mw is observed under non-equilibrium adsorption conditions caused by Mw-dependent adsorption kinetics. These results provide physical insights into how chain adsorption, which is strongly modulated by polymer/substrate interactions, affects the Tg-confinement effect in polymer thin films.
Article Details
Journal Info
The Journal of Chemical Physics
American Institute of Physics
Authors (5)
Lu Bai
Beijing Key Laboratory of Solid-State Battery and Energy Storage Process, Key Laboratory of Green Process and Engineering, State Key Laboratory of Mesoscience and Process Engineering
Weizhao Ren
Key Laboratory of Surface and Interface Science of Polymer Materials of Zhejiang Province, Department of Chemistry, Zhejiang Sci-Tech University , Hangzhou 310018,
Xiaonan Li
Jianquan Xu
Key Laboratory of Surface and Interface Science of Polymer Materials of Zhejiang Province, Department of Chemistry, Zhejiang Sci-Tech University , Hangzhou 310018,
Xinping Wang
State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, University of Chinese Academy of Sciences