Radiation-induced structural changes

A BC NMR Study of Radiation-Induced Structural Changes in Polyethylene... 

The problems involved in observing resonances from gelled polyethylene were also encountered in this study. We decided, therefore, to examine polyethylene samples irradiated with absorbed doses less than the gel dose. By so doing, some of the radiation induced structural changes produced prior to gelation could be detected. 

Radiation induced structural changes in polyethylene have been investigated for over 30 years. These studies have shown that the principal chemical changes which occur during irradiation are ... 

Since the vibrational spectra of sulfur allotropes are characteristic for their molecular and crystalline structure, vibrational spectroscopy has become a valuable tool in structural studies besides X-ray diffraction techniques. In particular, Raman spectroscopy on sulfur samples at high pressures is much easier to perform than IR spectroscopical studies due to technical demands (e.g., throughput of the IR beam, spectral range in the far-infrared). On the other hand, application of laser radiation for exciting the Raman spectrum may cause photo-induced structural changes. High-pressure phase transitions and structures of elemental sulfur at high pressures were already discussed in [1]. 

Tashiro, M., Pujari, P.K., Seki, S., Honda, Y., Nishijima, S., Tagawa, S. (2000) Studies on thermally induced structural changes in silicon based polymers by positron annihilation . Radiation Physics and Chemistry. 58, 587. 

The electron irradiation of linear and branched polyethylenes causes several molecular rearrangements in the polymer structure [59]. In addition to the significant changes in the type and distribution of unsaturated groups, IR comparison of the radiation-induced chemical changes that occur in air and in a vacuum showed that oxygen has a marked influence on the structural rearrangements that occur on irradiation. 

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