Thermoreactive benzotriazolylimides with hexamethylene bridging and terminal maleimide groups

Abstract

This article is devoted to syntheses of thermoreactive benzotriazolylimide resins with the hexamethylene bridging and terminal maleimide groups and a study of their structure, as well as properties of materials based on such resins. These resins are cross-linked under the action of high temperatures into three-dimensional polymers without the release of low-molecular-weight by-products. Three-dimensional polymers of such a type are of interest from the point of view of the availability of precursor materials, the ease of the preparation of the initial thermoreactive resins in the melt and high-performance characteristics. One-step melt synthesis without the release of by-products and in the absence of organic solvents is most acceptable from the technological and environmental points of view. The structure of the resins was confirmed by the IR and NMR spectroscopy data. Model compounds were synthesized and a comprehensive study of their structure by the spectroscopic methods was carried out. This was necessary for obtaining valuable information for the synthesis of the resins and to facilitate confirmation of their chemical structure. According to thermogravimetry data, the temperatures of beginning decomposition of resins in air are 350–360°C. For compounds containing the aliphatic units, this is a fairly high indicator. This fact is explained by the formation of cross-linked polymers before the onset of thermal destruction. The long curing time of resins up to 12 h ensures that heat generated during this process has time to dissipate without causing local overheating of the material that could cause the mechanical stresses. This improves the mechanical characteristics of materials based on these resins. The resulting materials are resistant to high temperatures and acidic aggressive environments (for example, H₃PO₄). This allows them to be used as thermoreactive binders for the manufacture of high-heat-resistant adhesives, as well as structuring components of polybenzimidazole polymer matrices for the manufacture of the proton-conducting membranes for the medium-temperature fuel cells. The positive effect of introducing the benzotriazolyl fragments into the structure of the thermoreactive resins on the mechanical properties of adhesive joints between steel plates has been shown.