Study of the Chemical Environment inside Free Volume Holes in Halogenated Styrene Polymers Using Positron Annihilation Spectroscopy

Zhang, Renwu; Robles, Jessica S.; Kang, Ji‐Hwan; Samha, Hussein; Chen, H. M.; Jean, Y. C.

doi:10.1021/ma300007p

Cited by 19 publications

(31 citation statements)

References 31 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…5(a) and 5(b), respectively, for PVC-EVA and PVC-SAN. Using the standard interpretation of the conventional S and W parameters [2,9,38], the plots producing straight line graphs suggest the presence of only one type of vacancy or open space in the region where the positrons annihilate. For polymers and blends the free volume cavities are larger vacancies than the crystalline defects.…”

Section: Line Shape Parameters S and Wmentioning

confidence: 99%

Influence of polar groups in binary polymer blends on positronium formation

et al. 2013

View full text Add to dashboard Cite

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.

show abstract

Section: Line Shape Parameters S and Wmentioning

confidence: 99%

Influence of polar groups in binary polymer blends on positronium formation

et al. 2013

View full text Add to dashboard Cite

show abstract

“…It is the ratio of the area under the wings in a fixed window divided by the total area. 24,[33][34][35] The momentum conservation in the annihilation process gives rise to a Doppler shift in the energies of individual g rays. For positrons localized in open-volume defects, the fraction of valence electrons taking part in the annihilation process increases compared to that of core electrons, and because the momentum of valence electrons is significantly lower, the momentum distribution of annihilating electrons shifts to smaller values.…”

Section: Pasmentioning

confidence: 99%

“…W is more sensitive to the chemical environment than S, as core electrons have a higher momentum, and thus contributes mainly to the high-momentum regions of the spectra. [33][34][35] The diffusion of AgNPs has a direct influence on the free volume of a polymer, and the diffusion of the dopant in such systems is controlled by the free volume and its content. Hence, the o-Ps s 3 and I 3 are the most appropriate lifetime parameters for understanding the free-volume modifications because of the diffusion of AgNPs into PC.…”

Section: Pasmentioning

confidence: 99%

Structural and antibacterial properties of a γ‐radiation‐assisted,in situprepared silver–polycarbonate matrix

Deore

Hareesh

Ramya

et al. 2016

J of Applied Polymer Sci

View full text Add to dashboard Cite

A silver–polycarbonate (Ag–PC) matrix was prepared by a γ‐radiation‐assisted diffusion method, and its antibacterial properties were studied. Rutherford backscattering spectroscopy, X‐ray diffraction, and transmission electron microscopy results showed the diffusion of good, crystalline‐structured (face‐centered cubic) silver nanoparticles (AgNPs) inside polycarbonate (PC) after irradiation. Ultraviolet–visible spectroscopic results indicated a blueshift in the surface plasmon resonance of the AgNPs; this revealed a particle size decrease with increasing γ‐radiation dose. This was also supported by the scanning electron microscopy results. The microstructure of the pristine PC and silver‐doped PC was monitored with positron annihilation spectroscopy, and it showed decreases in the free‐volume hole size and fractional free‐volume for Ag–PC and γ‐ray‐irradiated PC. This corroborated the Doppler broadening spectroscopy results. The thermal degradation temperature of PC was increased because of the diffusion of AgNPs in PC. The antibacterial activity of the synthesized Ag–PC matrix was evaluated by the zone of inhibition, and the results demonstrated its bacterial growth inhibition ability. The results indicate the potential to produce an Ag–PC matrix for various applications in medical and food industries. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43729.

show abstract

“…size, density and size distribution), determined by ortho-positronium (o-Ps) lifetime and its corresponding intensity, have been widely used to explain the physicochemical or macroscopic properties correlated with sub-nanoscopic structural feature of polymeric material. However, little attention has been paid to the chemical surrounding of positron trapping sites in polymers, though it is of essential to the cognition of relevant positron annihilation characteristics [4,5]. Numerous studies indicate that the trapped positrons annihilate with the surrounding electrons, conveying useful information on the local electronic environment around the annihilate sites, and thus the high sensitivity of positrons to local chemical environment is well documented [6][7][8].…”

Section: Introductionmentioning

confidence: 99%

Chemical Information of Chitosan-Based Complex Extracted from Coincidence Doppler Broadening Spectra

et al. 2017

View full text Add to dashboard Cite

In recent years, coincidence Doppler broadening (CDB) of annihilation radiation measurement on polymeric system has been attracting special attention because of its unique elemental sensitivities in comparison to the traditional Doppler broadening measurement. In the present study, chitosan-Fe3O4 nanocomposite (CS-Fe3O4) and copper-chitosan (Cu-CS) complexes were prepared through a simple casting method from aqueous solution. The inclusion of Fe3O4 nanoparticles in the chitosan matrix is confirmed by X-ray diffraction. In order to obtain data about atomic composition of the annihilation site in the CS composites, CDB measurements were carried out. The normalized CDB ratio curve, which is related to the ratio between the momentum density distribution for the studied samples and pure CS, was displayed to illustrate the variation of ion cores of different elements present in the chitosan matrix. Our result confirms a contribution of active group available in chitosan molecules to the features in the high-momentum region of the CDB ratio curve. The findings show that the local chemical environment of the annihilation site in chitosan-based complexes could be estimated by such positron annihilation spectroscopic investigation.

show abstract

Study of the Chemical Environment inside Free Volume Holes in Halogenated Styrene Polymers Using Positron Annihilation Spectroscopy

Cited by 19 publications

References 31 publications

Influence of polar groups in binary polymer blends on positronium formation

Influence of polar groups in binary polymer blends on positronium formation

Structural and antibacterial properties of a γ‐radiation‐assisted,in situprepared silver–polycarbonate matrix

Chemical Information of Chitosan-Based Complex Extracted from Coincidence Doppler Broadening Spectra

Contact Info

Product

Resources

About