Hybrid nanocomposites based on novolac resin and octa(phenethyl) polyhedral oligomeric silsesquioxanes (POSS): miscibility, specific interactions and thermomechanical properties

Hybrid nanocomposites were prepared via solution blending of octaphenethyl POSS into novolac resin. The resulted hybrid blends were investigated by Fourier-transformed infrared spectra (FTIR), polarized optical microscopy (POM), wide X-ray diffraction and differential scanning calorimetry (DSC). FTIR results showed that there existed intermolecular hydrogen bond between the hydroxyl groups of the phenolic resin and POSS siloxane groups, which could promote POSS to disperse well in the polymer matrix up to 20 wt% POSS loading. At higher POSS loading, POSS would aggregate and lead to macrophase separation, which was demonstrated by POM, DSC and WXRD. Finally, hexamethylene tetramine was used to cure the novolac blends to form hybrid network phenolic nanocomposites. Dynamic mechanical analysis results showed that the storage modulus of the hybrid networks was improved up to 20 wt% POSS loading; the T _g was increased with increasing POSS content and higher than that of the control phenolic resin except that 5 wt% POSS loading. Thermo gravimetric analysis showed that the thermal stability of hybrid networks was also enhanced with the incorporation of POSS.