Molecular relaxations of a branched poly(oxyethylene) network polymer

Abstract

Dielectric relaxation measurements and 13C NMR measurements were carried out on an amorphous network polymer derived from poly[2-(2-methoxyethoxy)ethyl glycidyl ether]triol with 2,4-toluenediisocyanate. The main relaxation and the higher frequency relaxation were observed in the dielectric spectra. The main relaxation was found to be symmetrical and broad with a half width of 5 decades in a frequency domain. The higher frequency process is considered to be the γ process of ethylene oxide chains due to the local twisting mode. The temperature dependence of T1 and T1ρ of the ethylene oxide carbon showed minima and it is clearly shown that the relaxation times obtained from the dielectric measurements correspond to the relaxation time obtained from the T1ρ measurements of the ethylene oxide carbon. The temperature dependence of T1 was well described assuming the Cole-Cole spectral density function with the shape factor β obtained for the dielectric main relaxation. The 13C magnetization decay of the ethylene oxide carbon in the rotating frame was found to be given by two components (slow and fast components) below the relaxation temperature. The broad dielectric relaxation and the decay profiles of the ethylene oxide carbon are discussed in terms of the branched structure of the network.