Prepolymer having more than one alkoxysilyl function per chain end reactive towards epoxide groups, as a constituent of a curable composition, is claimed. Independent claims are included for: (1) a composition comprising the prepolymer; (2) adhesively bonding surfaces or three-dimensional composite materials, comprising foaming an optionally foamable composition between the adherend surfaces to form a foam, applying the foam to one of the adherend surfaces or between the adherend surfaces, and subsequently compressing the foam between the adherend surfaces; and (3) a polymeric material, if appropriate with a foam-like structure, obtained by free or catalytically induced curing of compositions comprising the prepolymer.