A reversible epoxy polymer obtainable by the reaction between at least one epoxy compound and at least one curing agent, wherein at least part of the epoxy compound contains one reversible borate moiety or derivative thereof per molecule; and/or at least part of the curing agent contains one reversible borate moiety or derivative thereof per molecule; and/or the reaction system further comprises at least one compound containing hydroxyl and epoxy group and at least one BQH-containing compound or its ester derivative, wherein said BQH-containing compound contains two or more B-QH moieties, and wherein the derivative of borate moiety represents a moiety with the oxygen in the borate moiety being replaced with other element of the sixth main group and wherein each Q is independently an element of the sixth main group.