A Novel Photocrosslinkable Polyhedral Oligomeric Silsesquioxane and Its Nanocomposites with Poly(vinyl cinnamate)

A novel photosensitive octacinnamamidophenyl polyhedral oligomeric silsesquioxane (OcapPOSS) was synthesized via the reaction between cinnamoyl chloride and octaaminophenyl polyhedral oligomeric silsesquioxane (OapPOSS). The photosensitive OapPOSS was characterized by Fourier transform infrared (FTIR), nuclear magnetic resonance (NMR), and ultraviolet (UV)-visible spectroscopy. The full miscibility of OcapPOSS with the photosensitive polymer poly(vinyl cinnamate) (PVCIN) allows one to prepare the PVCIN−OcapPOSS hybrid nanocomposites. By initiating in situ UV photocrosslinking reaction of PVCIN in the presence of the photosensitive OcapPOSS, the PVCIN−POSS nanocomposites were obtained with the content of POSS up to 40 wt %. In terms of the result of FTIR spectroscopy, it is noted that the photocrosslinking rates of the PVCIN/POSS hybrids were slightly lower than those of the precursors, which could be ascribed to the nanoreinforcement of POSS cages on the polymer matrix. The inclusion of POSS cages could restrict the mobility of PVCIN macromolecular chains and thus hinder the formation of tetrabutane rings. The differential scanning calorimetric (DSC) results showed that the glass transition temperatures (Tgs) of the nanocomposites were significantly higher than that of the control PVCIN. Thermogravimetric analysis (TGA) showed that all the PVCIN nanocomposites containing POSS displayed the improved thermal stability. The high char yields of PVCIN nanocomposites also suggest improved flame retardence. It is plausible to propose that the improvement in weight retention is ascribed to the POSS constituent, which participated in the formation of the homogeneous hybrid network.