Synthesis, Heat Resistance, and Mechanical Properties of Cross-Linked Urethane–Imide Copolymers Containing Blocks of Two Structurally Different Aliphatic Fragments (Polyether and Polyester) in the Backbone

Multiblock (segmented) copoly(urethane–imides) were prepared using as monomers toluene 2,4-diisocyanate-terminated aliphatic polyether and polyester [poly(propylene glycol), poly(1,6-hexanediol/neopentylene glycol-alt-adipic acid)], aromatic diamines [1,4-bis(4'-aminophenoxy)biphenyl sulfone or 4,4'-bis(4''-aminophenoxy)biphenyl in a mixture with 3,5-diaminobenzoic acid], and 1,3-bis(3',4-dicarboxyphenoxy)benzene dianhydride. Each of the polymers contains two structurally different soft polyether/polyester segments and two identical hard imide segments, into one of which the reactive carboxy group is introduced. The covalent cross-linking of the copolymers was performed by the reactions of the carboxy groups with aromatic diisocyanates (toluene 2,4-diisocyanate, biphenylmethane 4,4'-diisocyanate) and 1,2,5,6-diepoxycyclooctane. The cross-linked polymer systems obtained were studied by thermal gravimetric analysis, differential scanning calorimetry, and dynamic mechanical analysis. The kind of cross-linking agent influences the properties of cross-linked copoly(urethane–imides). Variation of the mechanical loss tangent tan δ and width of the temperature interval of the transition from glassy to rubber-elastic state in relation to the chemical structure of copoly(urethane–imides) was analyzed. For the polymers under consideration, the maximal tan δ values exceed 0.3, which indicates that these polymers exhibit the damping ability.