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Positron annihilation lifetime spectroscopy (PALS) is a recognized method for the studies of nanoporosity (size distributions of nanopores) in solids. However, until recently [1], no attempts were made to estimate the concentration limits of sensitivity of this method to elementary free volumes (EFV). The reason was that no alternative methods applied to the same problem were discussed together. Meanwhile, the studies of nanoporosity are extremely important for creation of novel polymer membrane materials and sorbents with the unique permeation, selectivity and specific surface. They are used in solving the problems of ecology, chemistry and medicine. One of the most popular methods which are an obvious alternative or addition to PALS is the low temperature gas sorption (LTGS). In this report we consider results of several investigations of polymer membrane materials and sorbents where the both PALS and LTGS are applied to the same objects. All nanoporous polymers are ranked in Table 1 according to the pore size (micropore or nanopore) and condition of the material (ready made membrane or powder). The last specificity, condition, springs up because the process of membrane casting is able to change an accessible free surface, to slow down an adsorption rate compared to those of the natural free volume structure of the given membrane material. Therefore, we have to distinguish the two kinds of the objects. Sometimes, this may be important for LTGS but not essential for PALS or vice versa. Thus, Table 1 shows which of the two methods is adequate for investigation of the chosen materials.

Nanoporosity of Polymer Sorbents and Membrane Materials as Seen by PALS and Low Temperature Gas Sorption