ABSTRACT
The reverse process of the surface configuration change when liquid water is removed is an entirely different process driven by the different driving force as described before. Therefore, the recovery is generally much slower than the disappearance in water immersion, and the complete or large extent of recovery is not anticipated. In dry air, dehydration of the top surface seems to occur creating a less hydrated skin, which slows down the dehydration of the remaining film and reduces the rate of recovery observable by F/C ratio. The wet environment (in water vapor) allows rehydration of the freeze-dried sample from the top surface or reduces the dehydration at the top surface to form skin and makes rearrangement of polymer segments easier. The ironing seems to raise the temperature of the top surface quickly without removing existing water in the surface state and facilitate the segmental motion of polymer near the top surface. All of these data indicate the importance of w interaction in the surface dynamic change of hydrophilic polymers.
The fact that the very fast disappearance of surface fluorine atoms on water immersion was observed for the highly crystalline cellulose rather than the amorphous cellulose acetate suggests that the hydrophilicity or swelling capability (by water) of a polymer is more important than the degree of crystallinity.
