DYNAMICS OF THE SURFACE CONFIGURATION CHANGE OF POLYMERS IN RESPONSE TO CHANGES IN ENVIRONMENTAL-CONDITIONS .2. COMPARISON OF CHANGES IN AIR AND IN LIQUID WATER

The change of electron spectroscopy for chemical analysis (ESCA) F1s/C1s peak area ratios of plasma-fluorinated (by CF4 plasma treatment) poly(ethylene terephthalate) (PET), Nylon 6, and poly(methyl methacrylate) (PMMA) samples was observed as a function of time and temperature of dry heat treatment. The results of dry heat treatment are compared with the similar results obtained when samples are immersed in water. The decrease of the ratio is observed in both cases which indicates that F atoms disappear from the top surface region of samples as a consequence of these treatments. The surface configuration changes in response to the changes in the contacting medium are interpreted on the basis of the concept of the surface state of the polymer which tends to equilibrate with a new surrounding medium. Arrhenius plots of the rate constants of such decays showed conspicuous breaks at characteristic surface transition temperature T(s). In the case of dry heat treatment, T(s) represents the change of mobility of a polymer and corresponds to T(g) of the polymer. In the case of water immersion, T(s) represents the change of driving force due to the change in basic properties of water in contact with a surface (vicinal water) at the major Drost-Hansen temperature at 15-degrees-C and is independent of T(g) of the polymer. The activation energies for the surface configuration change in the dry heat treatment are found to be greater than those for the water immersion case; however, the differences are relatively small. Results indicate that the surface configuration changes do not require large segmental motions or migration of macromolecules. Motions responsible for surface configuration changes could be well perceived as relatively small rotational motions such as the ones seen in sub-beta-transition temperatures. Therefore, depending on the nature of the driving force, a significant extent of the surface configuration change can take place at temperatures substantially below T(g) of the polymer.