Poly positron lifetimes

Wang, C.L., Kobayashi, Y., Togashi, H., Kato, K., Hirotsu, T., Hirata, K., Suzuki, R., Ohdaira, T., Mikado, T. (1999) Plasma-polymerized hexam-thyldisiloxane films characterized by variable-energy positron lifetime spectroscopy . J. Appl. Poly. Sci. 74(10), 2522. 

Dlubek, G., Stejny, J., Lupke, T., Bamford, D., Petters, K., Hubner, C., Alam, M.A., Hill, M.J. (2001) Free-volume variation in polyethylenes of different cystallinities positron lifetime, density, and X-rays studies . J. Poly. Sci. Part B Poly. Sci. 40,65. 

H.E. Shaefer, R. Wurschum, R. Birringer and H. Gleiter, Structure of nanometer-sized poly crystalline iron investigated by positron lifetime spectroscopy. Phys. Rev. B, 38 (14) (1988) 9545. 

Polyesters. Positron lifetime techniques have been used to measure structural relaxation processes in irradiated poly(ethylene terephthalate) (PET). Three relaxation processes with different kinetics were observed in... 

Dlubek, G., Pionteck, J., and Kilburn, D., The structure of the free volume in poly (styrene-co-acrylonitrile) from positron lifetime and pressure-volume-temperature PVT) experiments I. Free volume from the Simha-Somcynsky analysis of PVT experiments, Macromol. Chem. Phys.,205, 500-511 (2004). 

Dlubek, G., De, U., Pionteck, J., Arutyunov, N., Yu. Edelmann, M., and Krause-Rehberg, R., The temperature dependence of free volume in semicrystalline poly(dimethylsiloxane) (PDMS) and its mixture with fumed silica from positron lifetime and PVT experiments, Macmmol. Chem. Phys., 206,827-840 (2005c). 

The second study (Meghala and Ranganathaiah 2012) was dedicated to the evaluation of interfaces in poly(styrene-co-acrylonitrile) (SAN)-based ternary polymer blends using also positron lifetime spectroscopy. The method successfully applied for binary blends (single interface), mentioned above, was theoretically modified for ternary blends and experimentally verified by measuring free volume content in blends and their constituents. They tested the efficacy of this method in two ternary blends S AN/PVC/PMMA and SAN/EVA/PVC at different compositions. The effective hydrodynamic parameter evaluated using individual values turned out to be handy in predicting the overall miscibility level of a ternary blend. 

Recent developments have been in the area of microthermal analysis using thermal conductivity with thermal diffiisivity signals or AFM to visualize specific areas or domains in the material and perform localized thermal analysis studies (183,184). Relaxational behavior over time and temperature is related to changes in free volume of the material. Positron annihilation lifetime spectroscopy (PALS) measurements of positron lifetimes and intensities are used to estimate both hole sizes and free volume within primarily amorphous phases of polymers. These data are used in measurement of thermal transitions (185,186) structural relaxation including molecular motions (187-189), and effects of additives (190), molecular weight variation (191), and degree of crystallinity (192). It has been used in combination with DSC to analyze the range of miscibility of polymethyl methacrylate poly(ethylene oxide) blends (193). 

It is evident from the above discussion that the free volume data derived from positron lifetime measurements is incapable of providing information on the composition-dependent miscibility level of the blend. At this point, a new method based on the same free volume data measured from positron lifetime measurements was introduced to determine the miscibility of binary blends. The new method was based on hydrodynamic interactions (the mathematics required have been explained in detail earlier), and calculations of the y parameter derived from the hydrodynamic interaction approach were made for three selected polymer blends, namely poly(styrene-co-acrylonitrile) (SAN)/poly(methyl methacrylate) (PMMA) (completely miscible), poly(vinyl chloride) (PVC)/poly(methyl methacrylate) (PMMA) (partially miscible) and poly(vinylchloride) (PVC)/polystyrene (PS) (immiscible) (see Figure 27.13). As can be seen, this parameter behaves similar to the interchain interaction parameter /3, in the sense that it exhibits a complex behavior making it difficult to determine the composition-dependent miscibility of the blends. 

K12 Kilbum, D., Dlubek, G., Pionteck, J., and Alam, M.A., Free volume in poly(n-alkyl methacrylate)s from positron lifetime and PVT experiments and its relation to the stmctural relaxation (experimental data by G. Dlubek), Polymer, 47, 7774, 2006. 

One of the main factors which needs to be considered in PAL analysis of polymers, is the affect which prolonged exposure to the positron source has on the lifetime parameters. It has been found that on prolonged exposure to a positron source, the o-Ps lifetimes are largely unchanged, but that there are significant variations in the o-Ps intensities for some polymers. Examples of these effects for a wide variety of polymers can be found polypropylene (PP), polyethylene (PE) [71], polystyrene [72], polycarbonates [73] poly(a-olefins) [49], poly(vinlyacetate) [74], poly(methyl methacrylate) [74] and a number of copolymers [75]. 

Bartos, J., Bandzuch, P., Suasa, O., Kristiakova, K., Kristiak, J., Kanaya, T., Jenninger, W. (1997) Free volume mircostructure and its relationship to the chain dynamics in cis-l,4-poly(butadiene) as seen by positron annihilation lifetime spectroscopy . Macromolecules, 30, 6906. 

Mazzroua, A., Mostafa, N., Gomaa, E., Mohsen, M. (2001) The use of positron annihilation lifetime technique to study the effect of doping metal salts on polyhydroxamic acid polymers . J. Appl. Poly. Sci. 81, 2095. 

FIGURE 9.6 Positron annihilation lifetimes at 303 K for (a) poly(vinyl acetate-co-vinyl alcohol) (PVAc-co-VOH) copolymers with poly(vinylpyrroMone) (PVP) and (b) polyvinylacetate (PVAc) with different vinyl acetate content. (From Cowie et al. [2001], with permission. Copyright 2001, American Chemical Society.)... 

Olson, B. G., Lin, J., Nazarenko, S., and Jamieson, A. M., Positron annihilation lifetime spectroscopy of poly(ethylene terephthalate) contributions from rigid and mobile amorphous fractions. Macromolecules, 36, 7618-7623 (2003). 

Schmidt, M., and Maurer, R H. J., Isotropic pressure-densihed atactic poly(methyl methacrylate) glasses free-volume properties from equation-of-state data and positron aannihilation lifetime spectroscopy. Macromolecules, 33, 3879-3891 (2000a). 

Raj et al. °" have compared the efficiency of microwave and e-beam irradiations to stabilize the interface of various partially miscible or nonmiscible blends polystyrene (PS)/polymethyl methacrylate (PMMA), polyvinyl chloride (PVC)/ethylene vinyl acetate (EVA), PP/acrylonitrile butadiene rubber (NBR), and polyvinyl chloride (PVC)/poly(styrene acrylonitrile) (SAN). For this purpose, they used positron annihilation lifetime measurements, and they considered particularly a hydrodynamic interaction parameter a. This... 

Another possible approach to indirectly characterize the membrane morphology is based on the investigation of the free volume within the matrix. Density measurements [119,120] and positron annihilation lifetime spectroscopy evaluation [47] are common methods. Typically, the comparison between the theoretical density or free volume (calculated by simple additivity rules) and the experimental one can reveal the presence of a good interfacial morphology or the presence of interface voids or clustering formation. Fig. 7.13 shows the influence of filler content on the morphology of poly(trimethylsilyl propyne) (PTMSP)/Ti02 NCMs in terms of the volumetric fraction of interface voids as calculated from a comparison of the expected and measured membrane density [119],... 

Winberg, P. Eldrup, M. Maurer, F. H. J., Nanoscopic Measurements of Silica Filled Poly(dimethylsiloxane) by Means of Positron Annihilation Lifetime Spectroscopy. Polymer 2004,45,8253-8264. 

Pore size and strain size studies. Carotenuto measured the average grain size of metal polymer nanocomposites [58] and Zamfirova and co-workers [59] carried out mean pore size measurements on poly(heptamethylene-p,p-tribenzoate) using X-ray diffraction and positron annihilation lifetime spectroscopy (PALS). 

Positron annihilation lifetime spectroscopy (PALS) is an efficient tool for measuring free volume and sizes of free volume elements in polymeric materials. This is particularly inq)ortant for studies of membrane materials, since free volume determines the permeation rate of small molecules. Free volume was studied by means of PALS in polymers characterized by extremely high permeability poly(l-trimethylsilyl-l-propyne) and copolymers of 2,2-bistrifluoromethyl-4,5-difluoro-l,3-dioxole and tetrafluoroethylene. The results obtained were compared with those observed for conventional glassy polymers. For the first time, the size distribution of free volume has been determined for these membrane materials. 

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