Synthesis and dynamic mechanical properties of cross-linked multiblock poly(urethane-imide) copolymers

Poly(urethane-imide) copolymers (PUICs) containing reactive carboxyl groups in hard imide segment were synthesized from poly(propylene glycol) with isocyanate end groups, 1,3-bis(3′,4′-dicarboxyphenoxy)benzene dianhydride, aromatic diamines 4,4′-bis(4″-aminophenoxy)diphenyl sulfone or 4,4′-bis-(4″-aminophenoxy)biphenyl, and 3,5-diaminobenzoic acid. The PUICs were covalently cross-linked using reactions of carboxyl groups with aromatic diisocyanates and 1,2,5,6-diepoxycyclooctane. The polymers obtained were studied by thermogravimetric analysis, differential scanning calorimetry, and dynamic mechanical analysis. It was shown that the structure of the cross-linking agents influences the properties of cross-linked PUICs. Changes in the mechanical loss factor (tg δ) were analyzed vs. chemical structure of the PUICs. The maximum tg δ values of the copolymers studied are in the range of 0.3–0.4, which suggests good damping capacity of these systems.