A crosslinked polymeric composition comprising A, B, C, D, and E units having the following structures, respectively:




and





wherein dashed bonds represent optional bonds; the asterisks (*) in C units represent covalent bond connection points with asterisks in A units and E units; the asterisks (*) in D units represent covalent bond connection points with asterisks in B units and E units; wherein a portion of E units are bound to C units, a portion of E units are bound to D units, and a portion of E units are bound to both C and D units; and the composition contains a multiplicity of A, B, C, D, and E units. Also described is a method for producing the crosslinked polymeric composition by reacting epoxy-containing molecules (A molecules), isocyanate-containing molecules (B molecules), and disulfide-containing molecules (C molecules).