Polybenzoxazine nanocomposites containing 3,13‐Diglycidyl double‐decker silsesquioxane

3,13‐Diglycidyloxypropyloctaphenyl double‐decker silsesquioxane (3,13‐diglydidyl DDSQ) was synthesized via hydrosilylation between 3,13‐dihydrooctaphenyl double‐decker silsesquioxane (3,13‐dihydro DDSQ) and allyl glycidyl ether. This novel difunctional polyhedral oligomeric silsesquioxanes (POSS) macromer was incorporated into polybenzoxazine (PBZ) thermosets to obtain the organic–inorganic nanocomposites. Compared to control PBZ, the organic–inorganic nanocomposites displayed the enhanced glass transition temperatures (T_g's). Under the identical condition, the organic–inorganic nanocomposites exhibited the stable rubbery plateaus in the measurements by dynamic mechanical thermal analysis, which was in marked contrast to control PBZ thermoset. The enhanced T_g's and improved dynamic mechanical properties are attributable to the formation of the additional crosslinking between PBZ and the difunctional POSS macromer and the nanoreinforcement of POSS cages on PBZ networks. Thermogravimetric analysis indicates that the organic–inorganic nanocomposites displayed improved thermal stability. POLYM. COMPOS., 38:827–836, 2017. © 2015 Society of Plastics Engineers