Studies on synthesis and characterization of multi-walled carbon nanotube-reinforced polyimide nanocomposites based on a siloxane-modified anhydride

Abstract

A novel series of multi-walled carbon nanotube (MWCNT) reinforced siloxane dianhydride based polyimide (PI) nanocomposites were designed and developed using in situ polymerization approach via thermal imidization. The polyamic acid obtained from the reaction of siloxane dianhydride and pyridine diamine/p-phenylenediamine was then incorporated with varying percentages of MWCNTs, which then undergoes thermal imidization to form MWCNT-PI nanocomposites. The synthesized PIs were then characterized using analytical methods. From thermal analysis, it can be seen that the glass transition temperature increased significantly by incorporating acid functionalized MWCNTs into the PI matrix than that of neat PI. This is due to the constraint effect of MWCNTs as well as the reduction in the movement of polymer chains. It exhibits an increased dielectric constant with the increase in weight percentage of MWCNTs to PI matrix. No aggregation and homogeneous dispersion of MWCNTs throughout the PI matrix have been achieved as evidenced by scanning electron microscopy and transmission electron microscopy. The newly designed PI system is responsible for the significant improvement of dispersion, thus enhancing attractive flame retardancy and dielectric properties.