| Abstract: | The kinetics of postpolymerization of γ-irradiated methacrylic acid at 77°K has been investigated by wide-line NMR and by ESR spectroscopy. The conversion yield was continuously measured in the temperature range of 260–280°K, from the narrowing of the NMR spectrum due to the progressive “amorphization” of the matrix, releasing the motion of monomer molecules. The rate of postpolymerization decays exponentially with time, independently of the recombination of free radicals. The local concentration of radicals remaining after prolonged annealing is actually the same as initially, showing that no recombination occurs in the microdomains of polymerization. The 13C NMR study of the poly(methacrylic acid) formed by solid-state polymerization shows a predominent syndiotactic character, with an increasing contribution of isotactic sequences as the postpolymerization temperature is lowered. |
