ACCELERATING EFFECT OF 3-AMINOPROPYLOLIGOMERIC SILSESQUIOXANE ON FORMATION KINETICS OF THERMOSTABLE HYBRID NANOCOMPOSITES BASED ON POLYCYANURATE NETWORK.

Abstract

In this work, reactive 3-aminopropyloligomeric silsesquioxane (AP-OSS) was synthesized and stu­died, and the effect of AP-OSS depending on its content (0.1–1.0 wt.%) on the kinetics of polycyclotri­merization of dicyanate ester of bisphenol E (DCBE) was determined using the dynamic DSC method. AP-OSS was prepared in high yield by the hydrolysis and polycondensation of 3-aminopropyltrimethoxysilane in a mixture of acetonitrile and ethanol, with tetrabutylammonium hydroxide (But₄NOH) as a catalyst. The chemical structure of the synthesized AP-OSS was confirmed by the results of FTIR and ¹H NMR spectroscopies, as well as by MALDI-TOF method. The FTIR spectra showed broad and intensive stretching absorption bands centered at ν≈ 3431 and ν≈ 3378 cm^–1 and bending absorption bands centered at δ≈ 1638 and δ≈ 1599 cm^-1 of the N–H in NH₂ groups, as well as the absorption bands centered at ν≈1027 and δ≈859 cm^–1, attributed to the special characteristic vibrations of the silsesquioxane cage Si–O–Si. MALDI-TOF spectroscopy detected predominantly singly charged protonatedions, indicating that the degree of oligomerization in this silsesquioxane is between n = 3 and 10. It was found that AP-OSS accelerated the DCBE polycyclotrimerization allowing decreasing the final temperature and time of polycyanurate network (PCN) synthesis, the higher content of the AP-OSS the higher acceleration effect has been observed. It was supposed that during the in situ synthesis of the hybrid PCN/AP-OSS nanocomposites, the amino groups on a surface of AP-OSS nanoparticles chemically interact with –O–C≡N-groups of DCBE with formation of isourea fragments providing the covalent embedding of  AP-OSS into the growing PCN matrix. Using DSC method, it was found that all synthesized hybrid  PCN/AP-OSS nanocomposites possessed high glass transition temperatures (T_g>280^oC) and can be classified as thermally stable polymer materials.