Effect of ultraweak neutron irradiation on the internal friction in poly(methyl methacrylate)

The effect of ultraweak neutron irradiation on the spectra of internal fric tion in PMMA samples of various molecular masses (M-w > 10(4)) was studied by method of dynamic relaxation spectroscopy. The exposure to a thermal neu tron flux results in a partial transition of the "free" COOCH3 groups and " free" macromolecular segments into a "bound" state with supersegmental orde ring. The new structural state is formed due to dipole-dipole interactions between the polar ester groups (pi-relaxation) and the intermolecular inter actions (X-relaxation), which sharply intensify the total (pi + chi)-relaxa tion process, The existence of locally ordered supersegmental structures fe aturing the interactions of both types may lead to certain changes in the d egree of stereoregularity of PMMA and to the formation of intermolecular hy drogen bonds related to the presence of atmospheric water vapors.