Influence of Chemical Reactions of Positronium on Annihilation Characteristics in Polymeric Sorbents

Size distribution of free volume holes for several types of polymeric sorbents based on crosslinked polystyrene was studied using the positron annihilation and Brunauer–Emmett–Teller low-temperature nitrogen sorption techniques. It turned out that the ranges of free volume size detectable by the positron and sorption techniques partially overlap, wherein the positron annihilation technique covers the region of nanopores and the sorption method covers submicronic pores and a part of nanopores. Thus, both methods well complement one another. Information obtained by means of the positron technique can be confused if the positronium atoms produced by positrons injected in a material of interest take part in chemical reactions. Cases when such reactions can be suppressed by lowering the temperature are discussed.