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 PL (10−3m0c). 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.
http://link.aps.org/doi/10.1103/PhysRevE.87.052602

Ureteral stents find wide application in urology. The majority of patients with indwelling ureteral stents are at an increased risk of urinary tract infection. Stent encrustation and its associated complications lead to significant morbidity. This review critically evaluates various polymers that find their application as ureteral stents with regard to various issues such as encrustation, bacterial colonization, urinary tract infections, and related clinical issues. A complete literature survey was performed, and all the relevant articles were scrutinized thoroughly. We discuss issues of encrustation=biofilm formation, new approaches to their testing, polymers currently available for use, new biomaterials, coatings, and novel ureteral stent designs, thereby providing a complete update on recent advances in the development of stents. Finally, we discuss the future of biomaterial use in the urinary tract.

We make molecular-dynamical study of the mechanism of thermally induced orientational disordering in a polymer crystal.
Doklady Physical Chemistry, Vol. 418, Part 2, pp. 15–18 (2008)