Polymerization by [3 + 2]-cycloaddition, 5. Telechelics with isocyanate end-groups

The “criss-cross” cycloaddition reaction between derivatives of benzaldehyde azine and several diisocyanates is used for the synthesis of polymers with an uncommon structure element: the 1,3,5,7-tetrazabicyclo[3.3.0]octane-2,6-dione. The nature of the diisocyanate determines the reactivity in this cycloaddition polycondensation and the solubility of the new polymers. A degree of polymerization up to P _n = 72 could be achieved. Due to the nature of the polycondensation reaction, the polymers have two isocyanate end-groups, independent of the stoichiometry of the monomer mixture at the beginning of the reaction. Thus, a prepolymer was synthesized and the chain extension by reaction of its isocyanate end-groups with diamines was studied in some detail.