title: Positron annihilation lifetime study of polyvinylpyrrolidone for nanoparticle-stabilizing pharmaceuticals.
abstract: Positron annihilation lifetime spectroscopy was applied to characterize free-volume structure of polyvinylpyrrolidone used as nonionic stabilizer in the production of many nanocomposite pharmaceuticals. The polymer samples with an average molecular weight of 40,000 g mol(-1) were pelletized in a single-punch tableting machine under an applied pressure of 0.7 GPa. Strong mixing in channels of positron and positronium trapping were revealed in the polyvinylpyrrolidone pellets. The positron lifetime spectra accumulated under normal measuring statistics were analysed in terms of unconstrained three- and four-term decomposition, the latter being also realized under fixed 0.125 ns lifetime proper to para-positronium self-annihilation in a vacuum. It was shown that average positron lifetime extracted from each decomposition was primary defined by long-lived ortho-positronium component. The positron lifetime spectra treated within unconstrained three-term fitting were in obvious preference, giving third positron lifetime dominated by ortho-positronium pick-off annihilation in a polymer matrix. This fitting procedure was most meaningful, when analysing expected positron trapping sites in polyvinylpyrrolidone-stabilized nanocomposite pharmaceuticals.
authors.affiliation: Institute of Physics of Jan Dlugosz University in Czestochowa, 13/15, Al. Armii Krajowej, Czestochowa 42200, Poland; Vlokh Institute of Physical Optics, 23, Dragomanov Str., Lviv 79005, Ukraine. Electronic address: olehshpotyuk@yahoo.com.
authors.forename: O
authors.initials: O
authors.lastname: Shpotyuk
authors.affiliation: Institute of Geotechnics of Slovak Academy of Sciences, 45, Watsonova Str., Košice 04001, Slovakia.
authors.forename: Z
authors.initials: Z
authors.lastname: Bujňáková
authors.affiliation: Institute of Geotechnics of Slovak Academy of Sciences, 45, Watsonova Str., Košice 04001, Slovakia.
authors.forename: P
authors.initials: P
authors.lastname: Baláž
authors.affiliation: Opole University of Technology, 75, Ozimska Str., Opole 45370, Poland.
authors.forename: A
authors.initials: A
authors.lastname: Ingram
authors.affiliation: Ivan Franko National University of Lviv, 1, Universytetska Str., 79000 Lviv, Ukraine; Centre for Innovation and Transfer of Natural Sciences and Engineering Knowledge, University of Rzeszow, 1, Pigonia Str., 35959 Rzeszow, Poland.
authors.forename: Y
authors.initials: Y
authors.lastname: Shpotyuk
mesh_terms: D008422:Materials Testing / Q000379:methods*; D053758:Nanoparticles / Q000032:analysis* / Q000737:chemistry; D011205:Povidone / Q000032:analysis* / Q000737:chemistry; D013059:Spectrum Analysis, Raman / Q000379:methods; D014961:X-Ray Diffraction / Q000379:methods
chemical_list: D011205:Povidone
keywords: Free-volume structure; Lifetime; Polyvinylpyrrolidone pharmaceutical; Positron annihilation