Shulzhenko D. The influence of amino-functionalized polyhedral oligomeric silsesquioxanes on the formation process, structure and properties of nanocomposites based on polycyanurate

Cyanate ester resins (CERs) occupy a special place among thermosetting resins, since their polycyclotrimerization results in the formation of densely crosslinked polycyanurate networks (PCNs) characterized by high glass transition temperatures, thermal and radiation resistance, low dielectric losses and water absorption, strong adhesion to metals, carbon- and glass-fiber composites, and high resistance to aggressive environments. These properties make them highly promising for applications in such high-tech industries as aerospace, microelectronics, shipbuilding, automotive engineering, and energy production. However, the synthesis of PCNs is a lengthy high-temperature process requiring the use of specific catalysts, often toxic, while the rigid structure of the polymer network necessitates its modification. A promising approach to addressing these challenges is the nanomolecular design of polycyanurate networks (PCNs) using reactive polyhedral oligomeric silsesquioxanes (POSS), which possess a closed inorganic siloxane cage structure with organic substituents bearing various functional groups. Functionalized POSS molecules can be covalently incorporated into the polycyanurate network as it forms in their presence (in situ method), becoming uniformly distributed throughout the PCN matrix. This results in a non-additive, synergistic enhancement of the physicochemical and mechanical properties, even at extremely low nanofiller loadings (≪1 wt.%). Therefore, the development of heat-resistant hybrid organic–inorganic PCN/POSS nanocomposites with tailored properties represents one of the important challenges in this field today. The main objectives of the study were: to develop in situ synthesis methods for hybrid organic–inorganic polycyanurate nanocomposites based on the dicyanate ester of bisphenol E (DCBE) using amino-functionalized POSS of different structures and reactivities, containing primary, secondary, or both primary and secondary amino groups in their organic substituents, and to determine the influence of their chemical structure and content on the formation of the hybrid polycyanurate network; to investigate the effects of reactive and inert nanofillers containing closed inorganic polyhedral cores of different structures and exhibiting different reactivities on the kinetics of DCBE polycyclotrimerization and the physicochemical properties of the resulting nanocomposites; to determine the kinetic characteristics of the chemical incorporation of amino-functionalized POSS with different functionalities into the forming polymer network; to evaluate the influence of the amino-POSS dispersion method in DCBE on the structure and overall properties of the resulting nanocomposites; and to establish the relationships between the structure and the thermal, thermophysical, viscoelastic, gas transport, and water absorption properties of the developed heat-resistant hybrid PCN/amino-POSS nanocomposites.