Organic-inorganic polybenzoxazine copolymers with double decker silsesquioxanes in the main chains: Synthesis and thermally activated ring-opening polymerization behavior

A series of organic-inorganic polybenzoxazine (PBZ) copolymers with double deck silsesquioxane (DDSQ) in the main chains were synthesized via Mannich polycondensation. First, 3,13-dianilino DDSQ a well-defined polyhedral oligomeric silsesquioxane (POSS) diamine was synthesized. Thereafter, this POSS diamine together with 4,4-diaminodiphenylmethane was utilized to react with 4,4'-dihydroxyldiphenylisopropane and formaldehyde to obtain the PBZ hybrids with DDSQ in the main chains. The high-molecular-weight products were obtained and they displayed excellent film-forming properties. Transmission electron microscopy showed that the PBZ-DDSQ copolymers were microphase-separated in bulks; the spherical POSS microdomains with the diameter of 10-20 nm were dispersed in the continuous PBZ matrix. Compared to plain PBZ, the PBZ-DDSQ copolymers displayed enhanced surface hydrophobicity as evidenced with the static contact angle measurements. These PBZ-DDSQ copolymers can easily undergo the thermally-activated ring-opening polymerization and the organic-inorganic thermosetting nanocomposites were obtained. The curing kinetics showed that the inclusion of DDSQ in the main chains of PBZ enhanced the activation energy of curing reaction. All the organic-inorganic thermosets possessed the enhanced thermal stability as evidenced with thermogravimetric analysis. (C) 2016 Elsevier Ltd. All rights reserved.