Host: The Japan Society of Vacuum and Surface Science
In this work, it reported the different contributions in thickness change of polymer ultrathin film with temperature. The boundary condition, such as interface layer and surface layer, was proposed that it may cause negative thermal expansion or asymmetric swelling under the ambient conditions. Generally, the constrained interface layer can form with the interface interaction with enough thermal treatment. In the polymer ultrathin film system, such as polyvinyl acetate ultrathin film, the negative thermal expansion has been observed, which would be caused by the different coefficient of thermal expansion between the interface layer and its adjacent region. On the other hand, the free surface layer may also contribute thickness change with the interaction with moisture. In the poly(N-isopropylacrylamide) (PNIPAM) ultrathin film, the asymmetric swelling has observed, which was proposed that it may be caused by local transition in the surface layer.
