High‐performance nanocomposites derived from allyl‐terminated benzoxazine and octakis(propylglycidyl ether) polyhedral oligomeric silsesquioxane

Abstract In this study, we used the Mannich condensation of bisphenol A, formaldehyde, and allylamine to synthesize a allyl‐terminated benzoxazine (VB‐a), which can be polymerized through ring opening polymerization. We used this VB‐a monomer, blended with octakis(propylglycidyl ether) polyhedral oligomeric silsesquioxane (OG‐POSS), to prepare polybenzoxazine/POSS nanocomposites. Differential scanning calorimetry and Fourier transform infrared (FTIR) spectroscopy revealed that the mechanism of the crosslinking reaction leading to the formation of the organic/inorganic network involved two steps: (i) ring opening and allyl polymerizations of VB‐a and (ii) subsequent reactions between the in situ‐formed phenolic hydroxyl groups of VB‐a and the epoxide groups of OG‐POSS. Dynamic mechanical analysis revealed that the nanocomposites had higher mechanical properties than did the control VB‐a. In the glassy state, nanocomposites containing less than 10 wt % POSS displayed enhanced storage moduli; those of the nanocomposites containing greater than 10 wt % POSS were relatively low, due to aggregation, as determined using scanningelectron microscopy. Thermogravimetric analysis indicated that the nanocomposites possessed greater thermal stability than that of the pure polymer. FTIR spectroscopic analysis revealed the presence of hydrogen bonding between the siloxane groups of POSS and the OH groups of the polybenzoxazine. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers