Abstract
AbstractResonance Raman spectroscopy has been used to measure the frequencies of the vibrational modes of the polymer backbone of fully and partially polymerized crystals of an ethyl urethane diacetylene. The data have assisted in the assignment of crystallographic structures to the different modifications of the crystals. Effective interatomic force constants have been derived and used to estimate the Young's modulus. For fully polymerized crystals a value of approximately 76 GPa was found. The dependence of the frequencies on elastic tensile strain parallel to the polymer chain direction was determined. By comparing the strain dependence of frequencies of partially polymerized singlecrystal fibers with those expected for model composites, it was concluded that the polymer chains in thermally polymerized crystals are considerably longer than in those polymerized using γ rays.
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