title: Influence of polar groups in binary polymer blends on positronium formation.
abstract: The present work studied the role of the polar group unconjugated oxygen on the inhibition of positronium (Ps) formation in two binary blends made from a set of chosen constituent polymers with polar and weakly polar groups (nonpolar). The polymer blend samples of PVC-EVA and PVC-SAN were investigated by coincidence Doppler broadening and positron lifetime techniques. The strong polar acetate group in the EVA contributed to positron annihilation with electrons of unconjugated oxygen (-C(+)=O(-)) as revealed by the momentum distribution curves peaking around 17 P(L) (10(-3) m(0)c). The ortho-Ps intensity indicated the unconjugated oxygen shows about a 28% Ps reduction even in the presence of a strong Ps inhibiting halogen (Cl(-)). In contrast, this effect was not seen in the PVC-SAN blends since SAN contains a weakly polar (nonpolar) acrylonitrile group (C≡N). Our results indicate the chlorine of PVC in the blends is a major contributor to Ps inhibition through the formation of a (Cl(-)-e(+)) bound state but the unconjugated oxygen in EVA of the PVC-EVA blend also plays a similar, but lesser, role.
authors.affiliation: Department of Studies in Physics, University of Mysore, Manasagangotri, Mysore-570006, India.
authors.forename: P
authors.initials: P
authors.lastname: Ramya
authors.forename: P
authors.initials: P
authors.lastname: Guagliardo
authors.forename: T
authors.initials: T
authors.lastname: Pasang
authors.forename: C
authors.initials: C
authors.lastname: Ranganathaiah
authors.forename: S
authors.initials: S
authors.lastname: Samarin
authors.forename: J F
authors.initials: JF
authors.lastname: Williams
mesh_terms: D003198:Computer Simulation; D004583:Electrons; D008956:Models, Chemical; D008958:Models, Molecular; D010100:Oxygen / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry*
chemical_list: D011108:Polymers; D010100:Oxygen