Thermal transitions and structure of epoxy networks based on α, ω-diamino terminated poly(propylene oxide)-block-poly(ethylene oxide)-block-poly(propylene oxide) swollen in water

Thermal transitions in epoxy networks prepared by reaction of α, ω-diamino terminated poly(propylene oxide)-block-poly(ethylene oxide)-block-poly(propylene oxide) and diglycidyl ether of brominated Bisphenol A, swollen in water, were studied by differential scanning calorimetry (DSC) in a broad temperature range (from -100°C to 20°C). Networks of two different values of initial molar ratio of amino and epoxy groups were prepared, r (r = 1.00, 2.00), and swollen with different amounts of water up to equilibrium concentration values. The qualitatively different kinds of experimental thermograms have been obtained for two networks and classified according to the amount of water in the sample on the basis of the phase diagram of the system. Also, the concentration dependence of the curves in this diagram (glass transition, melting, and crystallization) as well as the fraction of noncrystallizable water supply some information about the morphology of the system. In this sense, the existence of a microphase separated structure of swollen networks is suggested. The structure consists of hydrophilic and hydrophobic domains and depends on the initial molar ratio of the reactive groups.