We recently presented a short communication on the preparation of epoxy-based monoliths possessing highly ordered structures by polymerization induced phase separation based on the spinodal decomposition. In this article, we describe in detail on reaction mechanisms and structural properties of the epoxy-based monoliths with well-controlled macropores in the micrometer range. We prepared epoxy-based monoliths based on diglycidyl ether of bisphenol A, bis(4-aminocyclohexyl)methane, and polyethylene glycol with a bicontinuous structure by in situ step-growth polymerization. Different morphology of epoxy-based monoliths could be obtained by changing formulation of monomers and porogenic solvents. Characterizations of their morphologies were performed using scanning electron microscopy, mercury intrusion porosimetry, small angle X-ray scattering, and gas adsorption measurement (BET method). (C) 2008 Wiley Periodicals, Inc.