Dynamics of Reactive Polymer Networks in the Presence of a Nonpolar Solvent by Dielectric Relaxation Spectroscopy

An investigation was carried out on the dynamics of polymer networks in the presence of a nonpolar solvent. The formulations studied were composed of a network-forming multifunctional epoxy−amine mixture and o-terphenyl as solvent. A number of formulations at various degrees of cross-linking and with different solvent concentration were prepared and investigated. Experimental results were generated by simultaneous broad-band dielectric relaxation spectroscopy and remote fiber-optic Fourier transform infrared spectroscopy. The emergence of specific interactions during the network formation was confirmed by FTIR and their effect on the dynamics of the α process was established. Dielectric data were analyzed in the time and frequency domain, and it was found that the network dynamics could be classified into three regimes as a function of degree of cure. The nature of relaxations in these three regimes was discussed. An interesting finding was that the dynamics were dominated by the short-range interactions in the vicinity of the gel point. The presence of solvent had a pronounced effect on the various aspects of dynamics, including the apparent activation energy for the α process, the distribution function, and the cooperative nature of relaxations.