Transitions of the hydrogen bond in epoxy–diamine networks

The variation of the fundamental hydroxyl stretching frequency in the infrared spectrum of a number of epoxy–diamine networks has been determined as a function of temperature. Short‐range hydrogen bonds appear to be formed in all the epoxy networks examined. For polymers formed by using short‐chain α,ω‐diamines, it appears that a hydroxyl–hydroxyl bond is dominant. For longer chain lenghts, a hydroxylamine bond becomes important. The hydroxyl–hydroxyl bond breaks at the glass transition temperature, whereas the hydroxyl–amine bond breaks at a higher temperature. At the highest temperatures studied, all hydroxyl groups form weak short‐range bonds to the alkyl‐aryl ether function. The absorption frequency for the hydroxyl group in all types of hydrogen bonds formed shows a strong dependence on temperature and absorption moves to a higher wavenumber with increase in temperature.