Pal Application To the Study of Sorption Mechanism in Polymers - Capillary Effects

The positron annihilation lifetime technique can be applied to the study of the sorption mechanism in polymers in a quite unique way. In our previous experiments it had been shown that τ$\text{}_{3}$ and I$\text{}_{3}$ of polymers show a V-shaped dependence as a function of the contact with vapors. The decreasing part of the V-shaped dependence had been attributed to the Langmuir-type sorption, and the increasing part to delayed occurrence of the Henry-type sorption. But since there was some doubt that a capillary effect, i.e. the vapor to be sorbed is deposited in between the polymer membranes, might be involved in the increasing part, we performed a careful experiment to avoid the capillary effect. We have performed further experiments in a careful condition to avoid the capillary effect, and have observed the same V-shape as before. Thus our interpretation of the V-shaped dependence has been established. Furthermore, in another example it is shown a case where the capillary effect is observed. This latter case is an example how positron annihilation lifetime can distinguish the real sorption and false sorption (capillary effect).