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.

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Molecular imprinted polymer (MIP) with methacrylate acid (MAA) as monomer and ethylene glycol dimethacrylate (EGDMA) as cross-linker in different molar ratios has been prepared. The free volume size and distribution have been derived from the measured positron lifetime spectra in MIP. The free volume size distribution observed clearly indicates the influence of the amount of cross-linker in the sample. Present results suggest that the optimum monomer cross-linker ratio is 1:5 for this MIP. Fourier tranform infrared (FTIR) results confirm complete extraction of the 4-chlorophenol template molecules (4-CP) from the MIP with the absence of stretching frequencies at 648 and 825 cm–1 for the C–Cl group. The free volume distribution analysis indicates that the percentage of accessible cavities to 4-CP molecules in this MIP is only 85% and less than those values reported in earlier studies.

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