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In this work positron annihilation lifetime spectroscopy (PALS) is employed to study the ortho-Positronium lifetime parameters τ3>, σ3 and I3 in two structurally simple amorphous polymers 1,2-poly(butadiene) and cis-1,4-poly(isoprene). The ortho-Positronium mean lifetime parameter τ3> is compared with dynamics data from broadband dielectric spectroscopy (BDS) and electron spin resonance (ESR) experiments. Coincidences of characteristic temperatures from PALS with BDS and ESR experiments show close relationships between positron lifetime and dynamics of polymers.

Positron lifetime annihilation spectroscopy (PALS) was used to study the temperature- dependence of sub-nanometer size local free volumes in two atactic poly(n-octadecyl methacrylate)s (PODMA) with different molecular weight. These materials exhibit short range layered structure with a self-assembly and crystallization of side chains. From the ortho-positronium (o-Ps) lifetime the size of free volume holes and its distribution are calculated. At a temperature Tm=311 ± 5 K, the mean hole volume shows an abrupt and strong increase from 0.15 nm3 to 0.2 nm3, which comes from the melting of side-chains. The reverse effect, attributed to side chain crystallization, was observed during cooling the samples at slightly lower temperatures. The lifetime result of PODMA is compared with semifluorinated polyesters in which the side chain has an oxydecylperfluorodecyl structure (-O-(CH2)10-(CF2)9-CF3). Long chain polymers without side-chains such as polyethylene and short side-chain poly(n-alkyl methacrylate)s: poly(methyl methacrylate) (PMMA) and poly(n-hexyl methacrylate) (PHMA) are also compared with these polymers.

Changes in the free volume in CYTOP due to pressure densification and swelling with CO2have been examined using PALS and PVT experiments. Employing the SimhaSomcynsky equation of state the specific hole free, Vf, and occupied, Vocc, volumes were estimated. The change in the total volume due to the pretreatments occurs exclusively in the hole free volume and the relative change in Vfis one order of magnitude larger than in the total volume. Voccshows no memory for the history of the polymer glass. The mean and width of the size distribution of subnanometre holes in the glassy state decrease upon densification and increase upon swelling. The volume changes which are frozen in the polymer glass begin to recover at temperatures distinctly below Tg.

Summary: We analysed reported specific volume V from pressure-volume-temperature (PVT) experiments for poly(vinyl acetate) (PVAc) using the Simha-Somcynsky equation of state (S-S eos) and calculated the specific occupied volume, Vocc, and hole free volume, Vfh We found that Vocc shows almost no thermal expansion but is distinctly compressible (T > Tg). Due to this, Vfh = V − Vocc is not a unique function of V but can depend on the specific values of P and T giving rise to the particular value for V. We observed that with decreasing temperature the α-relaxation detected via dielectric measurements slows down faster than the shrinkage of hole free volume Vfh would predict on the basis of the free volume theory of Cohen and Turnbull. Vfh becomes zero at approximately 65 K below the Vogel temperature T0, $T'_0 = T_0 - 65\,{\rm K}$. Plots of the α‐relaxation frequency log ωα versus 1/Vfh can be linearised when taking into account this discrepancy by substituting 1/Vfh by 1/(Vfh − ΔV) with $\Delta V = E_{{\rm fh}} (T_0 - T'_0 )$, or by including an energy term of the type exp[−E′/R(T − T0)] in the pre‐exponential factor of the frequency‐volume equation. Our results indicate that the α‐relaxation in PVAc operates via the Cohen‐Turnbull mechanism only when liquid‐like clusters of cells of the S‐S lattice appear which contain a hole free volume of three or more empty S‐S cells. For regions with a smaller number of empty cells an activation energy is required for allowing segmental motion via the cooperative rearranging of cells. The β‐(Johari‐Goldstein) relaxation which is a non‐cooperative, more local, process follows completely the free volume theory. The same seems to be true for the primitive (uncoupled) relaxation of the coupling model.

Summary: The structure of the free volume and its temperature dependence between 25 and 190 °C of copolymers of styrene with acrylonitrile, SAN (0 to 50 mol-% AN), is studied by pressure volume temperature (PVT) experiments and positron annihilation lifetime spectroscopy (PALS). In this second part of the work, PALS data are reported from which the temperature dependence of the mean size and size distribution of local free volumes (subnanometer size holes) is analysed. The mean hole volume, vh, varies in PS between 105 ų (27 °C) and 220 ų (190 °C), and shows a systematic decrease with increasing AN content, at Tg from 121 ų for PS to 102 (±2) ų for SAN50. The specific number of holes, $N_{\rm h} '$, estimated from a comparison of PVT and PALS results, is independent on the temperature and the composition of SAN, $N_{\rm h} '$ = (0.56 ± 0.02) × 10²¹ g⁻¹ which corresponds to Nh(Tg) = $N_{\rm h} '$/V(Tg) = 0.59 nm⁻³ and 1/Nh(Tg) = 1.7 nm³ for the volume which contains one hole. The analysed size distributions of the holes above Tg follow the compressibility of the free volume as it is predicted by the theory of thermal volume fluctuation. Moreover, we showed that the bulk elasticity modulus follows mastercurves as a function of vh above and below Tg. Free volume hole radius distribution n(rh) in PS for three different temperatures.