Conformation-Sensitive Surface Dynamics in Thin Poly(ethylene terephthalate) Film

Abstract

The surface average conformation of poly(ethylene terephthalate) (PET) films was modulated by adjusting the water content in corresponding trifluoroacetic acid (TFA) spin-coating solutions, which was confirmed by surface-sensitive sum frequency generation (SFG) vibrational spectroscopy. Molecular dynamics simulation results showed that the added water molecules partly disrupt the hydrogen bond network between TFA molecules and PET chains and make it possible to preserve the statistical average bulk-like spherical conformation at the film surface during the formation of PET film. Slower surface crystallization kinetics, higher surface glass transition temperature (Tgsurface), and suppressed Tg-confinement effect were observed when the surface average conformation changed from oriented oblate ellipsoidal conformation to isotropic spherical conformation, showing that surface dynamics is very sensitive to chain conformation.