Small-angle neutron scattering study of nanophase separated epoxy hydrogels

A series of hydrophilic epoxy networks was prepared by end-linking reaction of α,ω-diamino terminated poly(oxypropylene)-block-poly(oxyethylene)-block-poly(oxypropylene) of average molar mass ca. 600 g mol−1 and diglycidyl ether of Bisphenol A propoxylate at various values of stoichiometric ratio, r, of amino to epoxy groups. Epoxy hydrogels were obtained by swelling of the epoxy networks in deuterated water. Nanophase separated structure of all hydrogels has been revealed by small-angle neutron scattering. The structure is much finer than that found in the similar system investigated previously which was prepared using much longer diamine (molar mass ca. 2000 g mol−1). Unlike the previous system, the scattering data from the present system cannot be fitted properly by Percus–Yevick model but Teubner–Strey model based on the locally lamellar order of nanophases dictated by conservation of polymer network topology proves well in the fitting. The values of parameters of the nanophase separated structure – two characteristic lengths: periodicity and persistence length of the locally lamellar order and their dependence on the network composition are determined and analyzed in detail.