Specifics of Positron Studies of Microheterogeneous Systems as Applied to New Polymeric Sorbents

The size distribution of free volume holes in mesoporous, microheterogeneous polymer sorbents based on linear rubber-modified divinylbenzene copolymers has been studied. Analysis of the results of the study and published data has shown that positron annihilation lifetime spectroscopy (PALS) applied to microheterogeneous systems, in contrast to homogeneous systems, is not necessarily sensitive to mesopores that occur at the boundaries of heterogeneities and determine the sorption or membrane properties of the modified materials. To obtain the complete information, additional procedures such as low-temperature (BET) gas adsorption and thermally stimulated luminescence (TSL) need to be used. This circumstance is due to a considerably long distance between mesopores in heterogeneous systems and limited mobility of positronium during its localization in a pore. In addition to the BET data, which largely give information on mesopores, PALS appears useful for studying micropores. The TLS technique makes it possible to judge on heterogeneity of test materials. The minimal concentration of mesopores detectable by the positron technique in the systems of interest has been determined.