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Kwon, Jun-Hyun; Truss, R. W.

doi:10.1023/a:1014921503505

Cited by 3 publications

(2 citation statements)

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“…X-ray diffraction and IR spectroscopy are both commonly used to assess crystallinity in PVC, − and both techniques clearly showed that stress increased the chain ordering in polymer 1 . In the case of IR spectroscopy, an increase in the absorbance ratio of the infrared peak at 635−638 to that at 610−615 cm -1 is indicative of an increase in crystallinity. − Figure S2 shows that the A 637 / A 615 ratio of polymer 1 increased with increasing stress. In the case of wide-angle X-ray diffraction, an increase in intensity of the (200) and (110) reflections (in the 16−18° 2θ region 33-35 ) has been shown to correlate with an increase in crystallinity in PVC.…”

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confidence: 99%

“…To our knowledge, this is the first experimental confirmation of the behavior predicted by the "decreased radical recombination efficiency" hypothesis in which oxygen diffusion is not a complicating factor. X-ray diffraction and IR spectroscopy are both commonly used to assess crystallinity in PVC, [28][29][30][31][32][33][34][35] and both techniques clearly showed that stress increased the chain ordering in polymer 1. In the case of IR spectroscopy, an increase in the absorbance ratio of the infrared peak at 635-638 to that at 610-615 cm -1 is indicative of an increase in crystallinity.…”

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confidence: 99%

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Investigation of the Origin of Tensile Stress-Induced Rate Enhancements in the Photochemical Degradation of Polymers

et al. 2004

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To investigate the effect of tensile stress on the photochemical degradation efficiencies of polymers, a modified PVC polymer with Cp(CO)3Mo-Mo(CO)3Cp (Cp = eta5-C5H5) units along the backbone was synthesized. The polymer is photochemically reactive because the Mo-Mo bonds are photolyzed with visible light and the resulting radicals are captured with Cl atoms from along the polymer backbone. Of most importance from a mechanistic standpoint, the photochemical degradation reaction occurs in the absence of oxygen, which eliminates the kinetically complicating effect of rate-limiting oxygen diffusion. Tensile stress initially caused the quantum yield of polymer degradation to increase, but, after a certain point, additional stress caused a decrease in the quantum yield. This dependence of quantum efficiency on stress is consistent with a hypothesis in which stress affects the ability of the photochemically generated radicals to recombine. At low to moderate stress, the effect of stress is to increase the separation of the radicals (by recoil), thus decreasing their recombination probability. As the stress increases, however, segments of different chains align, which induces a higher degree of orientation and crystallinity in the polymer, which in turn makes diffusion more difficult. The efficiency of degradation is predicted to decrease accordingly because of decreased radical and/or trap mobility in the ordered polymer. Infrared and X-ray data are presented, showing that the degree of orientation and crystallinity in the polymer does indeed increase with increasing stress.

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