Studies on thermal and dielectric properties of ether linked cyclohexyl diamine (ELCD)-based polyimide POSS nanocomposites (POSS-PI)

Polyhedral oligomeric silsesquioxane (POSS)-polyimide (PI) hybrid nanocomposites were prepared from ether linked cyclohexyl diamine (ELCD)-modified polyamic acid with POSS derivative of octaaminophenylsilsesquioxane (OAPS). Polyamic acid (PAA) was prepared by reacting ELCD with pryomelletic dianhydride (PMDA) in 1-methyl-2-pyrrolidone (NMP) medium. The PAA reacted with varying weight percentages of OAPS and undergoes thermal imidization to form POSS-PI nanocomposites upon heating. The formation of hybrid nanocomposites was confirmed with Fourier transform infrared spectra. The thermal and dielectric properties of POSS-PI nanocomposites were characterized by using differential scanning calorimetry, thermogravimetric analysis and an impedance analyzer. Morphology of the nanocomposites was studied by using scanning electron microscopy. Data from thermal studies indicated that the incorporation of POSS in to PI substantially enhanced the glass transition temperature ( Tg), thermal stability and char yield of hybrid nanocomposites in comparison with those of neat PI. From the dielectric studies it was inferred that the increasing percentage concentration of OAPS into the PI network exhibits a decreasing trend in the values of dielectric constant when compared with those of neat PI.