Preparation and Characterizations of Poly(amic acid) Grafted Silica Nanoparticles.

POly(amiC acid) grafted silica nanoparticles (PAA-SNs) were successfully prepared by the grafting polymerization of poly(amic acid)s based from the in-situ condensation polymerization of pyromellitic dianhydride (PMDA) and three diamines (4,4 ­diaminodiphenyl ether (DDE), 4,4 -diaminodiphenyl methane (DDM) and 4,4 -diaminodiphenyl sulphone (DDS)) from the surfaces of the y-aminopropyl silica nanoparticles (APSNs) with N,N-dimethyl acetamide (DMAc) as solvent. The products were characterized by elemental analyses (EA), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectrometry (XPS), thermogravimetric analysis (TGA) and transmission electron microscopy (TEM). The percentage of grafting (PGs) (the weight ratios of the PAA grafted and the charged silica nanoparticles) of PAADDE-SNs, PAADDM-SNs, PAADDS-SNs, calculated from the results of C elemental analyses (EA), were 56.77%, 38.97% and 46.05%, respectively. The TEM analysis showed that they could be dispersed in organic solvents. Therefore, the systems could be used as reactive nanofillers or nano-cross-linkers for polymer nanocomposites because of their better organic solubilities and the large numbers of carboxyl acid groups on their surfaces.