Positron annihilation lifetime data and actual porosity of polymers

Abstract

Application of the three‐component LT9.0 analyses and discrete four‐component PATFIT analysis to PAL distribution in some porous polymers, such as PIM‐1, AF2400, AF1600, PTMSP, give practically the same good fitting. In the conditions of this uncertainty, some additional experiments (thermomechanical tests, NMR on the protons of the absorbed water, thermo‐stimulated luminescence TSL, low temperature gas sorption BET, mathematic molecular‐dynamic simulation) give some arguments in favour of non‐Gaussian distribution of elementary free volumes EFV in some porous polymers and their possible heterogeneity. Furthermore, a comparison of PAL and TSL data confirm the idea on the interconnection between the rigidity of the polymer chains and effective size of the EFV. This interconnection is illustrated by the correlation of the o ‐Ps lifetime and intensity of the high‐temperature peak in the TSL glow curve. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Gas permeation parameters of mixed matrix membranes based on the polymer of intrinsic microporosity PIM-1 and the zeolitic imidazolate framework ZIF-8

“…Their analysis showed that somewhat better correlation with permeability was observed for the RTL parameter a. It confirms the trend reported earlier [80] for polymers with widely varied properties.…”

“…It permits one to work with very small samples (up 1-100 mg) in different form (films, fibers, powder, etc.). Recently, it was shown [80] that polymers of different structures having widely varying chain stiffness, free volume and glass transition temperatures reveal different type of emission trend. For polymers with relatively flexible chains (e.g., polyolefins) the main part of emission occurs at low temperatures (below 200 K), while for polymers having much more rigid chains such as amorphous Teflons, poly(trimethylsilyl propyne) etc., the fraction of light emitted in the range 200-380 K is much higher.…”

Local Rigidity as a Criterion of Gas Permeation of Polymer and Composition Materials; PAL and TSL Experiments

“…At low temperatures, intensity of the positronium formation and * corresponding author; e-mail: shant@center.chph.ras.ru integral intensity of TSL are dependent on the storage of the spur electrons (weakly bound electrons). The obtained results make another proof of the spur mechanism of positronium formation [9].…”

“…In its turn, the rigidity determines the shape of the curve of the integral intensity of the TSL. The shape is characterized in our case by relative intensity of the high temperature (above 200250 K) component (so-called parameter α) [9].…”

Specifics of positron studies of microheterogeneous systems as applied to new polymeric sorbents

“…At a low temperature, the positronium formation rate and the integrated (over wavelength) TSL intensity [14,15] depend on the buildup of weakly bound electrons (track electrons) and are prone to optical quenching (bleaching). These results are another piece of evidence for the spur mechanism of positronium formation [16,17].In [18][19][20], we showed the effectiveness of the combined use of the room temperature PALS and low temperature TSL methods for investigation of some new membrane materials including materials with a heterogeneous structure. The following logic was adopted.…”