title: Depth profile of free volume in a mixture and copolymers of poly(N-vinyl-pyrrolidone) and poly(ethylene glycol) studied by positron annihilation spectroscopy.
abstract: Effect of hydrogen bonding on the depth profile of the free-volume in a mixture (weight ratio of 65:35) of poly(N-vinyl-pyrrolidone) (PVP) and poly(ethylene glycol) (PEG) and the copolymers of vinyl pyrrolidone with poly(ethylene glycol) diacrylate (PVP-PEGDA) and monomethacrylate (PVP-PEGMMA) was studied using positron annihilation spectroscopy. Doppler broadening energy spectra of annihilation radiation and positron annihilation lifetime were measured as a function of positron incident energy (0-30 keV). Significant variations of the free-volume depth profile in terms of the S parameter, ortho-positronium lifetime, intensity, and lifetime distribution are observed as a result of the hydrogen-bonding replacement of covalent bonds. The polymer mixture with hydrogen bonding through two sides of PEG short chains has a larger free volume and a wider distribution than the comb-structured PVP-PEGMMA and the network structured PVP-PEGDA. A longer ortho-positronium lifetime is observed near the surface than in the bulk. This is interpreted in terms of surface effect, free volume, and hydrogen bonding for drug delivery applications of polymeric materials.
authors: Department of Chemistry, University of Missouri-Kansas City, Kansas City, Missouri, USA.
authors: Y
authors: Y
authors: Li
authors: R
authors: R
authors: Zhang
authors: H
authors: H
authors: Chen
authors: J
authors: J
authors: Zhang
authors: R
authors: R
authors: Suzuki
authors: T
authors: T
authors: Ohdaira
authors: M M
authors: MM
authors: Feldstein
authors: Y C
authors: YC
authors: Jean
mesh_terms: D004337:Drug Carriers / Q000737:chemistry; D004583:Electrons; D006860:Hydrogen Bonding; D011092:Polyethylene Glycols / Q000737:chemistry; D011108:Polymers / Q000737:chemistry*; D011205:Povidone / Q000737:chemistry; D013057:Spectrum Analysis
chemical_list: D004337:Drug Carriers; D011108:Polymers; D011092:Polyethylene Glycols; D011205:Povidone