On the relation between positron annihilation lifetime spectroscopy and lattice‐hole‐theory free volume

Abstract

A coincidence between the temperature‐dependent hole (free volume) fraction h above the glass transition temperature, derived from lattice‐hole theory, and the corresponding function hPs obtained from positronium lifetime spectroscopy has been previously observed for four polystyrene fractions ranging from 4000 to 400,000 in molar mass. This result was based on the assumed proportionality of hPs and the product of the orthopositronium intensity I3 and the mean cavity volume, the proportionality constant C being molar mass dependent. However, a recent analysis of the data based on volume arguments by Olson and Jamieson revealed systematic departures between the two sets of free volume functions. We reexamine the situation by departing from the customary assumption of spherical cavities, and allowing for nonspherical geometries represented by prismatic or cylindrical disks. Agreement between spectroscopic and thermodynamic functions ensues with fixed, temperature‐independent asymmetry factors decreasing with increasing molar mass. These tentative findings suggest that systematic studies of melts with varying chain flexibility and molar mass should be attempted. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2225–2229, 2005

Positron Annilation Lifetime and Glass Transition Temperatures in CO2Sorption Polystyrene

“…It is also interesting to observe that the ratio of α above and below T g for free volume (α r /α g = 4.6) is also larger than that from the bulk (= 2.6). These observations of o-Ps data vs. T are also in general consistent with the existing PAL data in PS [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32].…”

“…While PS have been extensively studied using PAL in recent years [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32], for CO 2 exposure, only up to 50 psi has been reported [13]. In this paper, we report the result of free-volume size and distribution and determine the variation of glass transition temperature (T g ) in polystyrene with and without CO 2 sorption under 400 psi pressure at different thermal cycles and compare with the DSC data.…”

Free volume dependence of polymer viscosity

“…Excepting the recent publications (Srithawatpong et al 1999;Olson et al 2002;Olson 2004;Schmidtke et al 2004;Consolati et al 2005), it has been assumed that the free volume cells, V 3 , are spherical. The quantum mechanical calculations (Tao 1972;Eldrup et al 1981) gave a semiempirical equation, relating the free volume cell radius, R, to the measured o-Ps lifetime, t 3 :…”

A Simplified Method for the Estimation of Hole Free Volume Fraction from the Specific Volume

“…These authors observed a linear relation between the van der Waals volume V W and V * and analysed V * = 1.45V W for polymers and V * = 1.60V W for low molecular liquids. The V * -values estimated by other groups [6][7][8] for several polymers correspond to V * /V W = 1.57-1.60. In Fig.…”

“…It was found that the vacancies of the S-S lattice form multivacancies or agglomerates due to their large concentration [5]. Ortho-positronium (o-Ps) annihilates from a state localised at one of theses multivacancies [6][7][8][9][10][11][12][13][14]. From its mean size, ν h , and the hole fraction h a realistic value for the hole density N h = h/ ν h can be estimated.…”