X-ray diffraction technique to assess radiation damage in semicrystalline polymers. I. Isotactic poly(methyl methacrylate)

By using x-ray diffraction the total damage to a semicrystalline polymer is determined after exposure to high-energy ionizing radiation. By rearrangement of the first-order dependence of the fractional change in crystallinity on the dose the number of chemical and/or physical changes per 100 eV of energy absorbed [i.e., G(-units)] is computed. In the present effort on isotactic poly(methyl methacrylate) (PMMA) the value of G(-units) is approximately equal to 15 confirms previous results obtained by cryoscopy, and thereby yields a ratio of ca 8:1 for chemical plus physical (i.e., total damage) versus chemical damage alone. From nuclear magnetic resonance (NMR) results, a partition of the physical damage into configurational and conformational changes yields G values of 6 and 7, respectively. 6 figures, 5 tables