A series of functional polyhedral oligomeric silsesquioxane (POSS)/polyimide (PI) nanocomposites were prepared using a two‐step approach. First, octa(aminophenyl)silsesquioxane (OAPS) was mixed with poly(amic acid) (PAA) prepared by reacting bis(4‐amino‐3,5‐dimethylphenyl)‐3‐quinolylmethane and 3,3′,4,4′‐benzophenonetetracarboxylic dianhydride. Second, the resulting solution was subjected to thermal imidization. The well‐defined ‘hard particles’ (POSS) and the strong covalent bonds in the amide linkage between the carbon atom of the carboxyl side group in PAA and the nitrogen atom of the amino group in POSS lead to a significant improvement in the thermal and mechanical properties. Homogeneous dispersion of POSS cages in the PI is evident from scanning electron microscopy, which further confirms that the POSS molecule becomes an integral part of the organic‐inorganic inter‐crosslinked network system. Differential scanning calorimetry and dynamic mechanical analysis show that the glass transition temperatures of the POSS‐containing nanocomposites are higher than that of the corresponding neat PI system, owing to the significant increase of the crosslinking density in the PI/POSS nanocomposites. Increasing the concentration of OAPS in the PI networks decreases the dielectric constant. Pure PI and PI/POSS systems have good antimicrobial activity. Copyright © 2011 Society of Chemical Industry

Polymer‐carbon nanotube nanocomposites are extensively investigated for microelectronics and aerospace applications. In this study, novel polyimide/f‐MWCNT nanocomposites made from 2,4‐bis(4‐aminophenylamido)‐6‐chloroquinazoline, pyromellitic dianhydride and functionalized‐Multi Walled Carbon Nanotubes (f‐MWCNT) by an efficient microwave assisted method were investigated. The structure of the prepared diamine monomer was confirmed by FT‐IR, 1H‐NMR, and 13C‐NMR spectral techniques. The prepared nanocomposites (Tg values from 338°C to 375°C) show improved thermal property as indicated by differential scanning calorimetry and thermogravimetric analysis. Polyimide/f‐MWCNT nanocomposites were found to have higher dielectric constant, and the limiting oxygen index values of prepared nanocomposites are in the range of 29.5 to 35.5, indicating a high flame retardancy. Additionally, the morphological studies were conducted by X‐ray diffraction and scanning electron microscopy. Overall, it is observed that chemically connected polyimide‐functionalized carbon nanotube nanocomposites could be used for aerospace and microelectronics applications that require high Tg, dielectric constant and high flame retardancy.

Polyimide-MWCNT nanocomposites were prepared by the reaction of a heterocyclic diamine monomer of bis(4amino-3,5-dimethylphenyl)-2-chloro-3-quinolylmethane (BACQM), pyromellitic dianhydride (PMDA) with unmodified MWCNT (MWCNT), acid-functionalized MWCNT (acid-MWCNT) or amine-functionalized MWCNT (amine-MWCNT) using microwave irradiation as well as by the conventional method. The structure of the monomer was confirmed by FTIR, 1 H-NMR, and 13 C-NMR spectral techniques. The glass transition temperature (T g ) of the MWCNTs/polyimide nanocomposite was found to be higher than that of the unfilled polyimide system. The T g 's of both systems were higher when prepared with the microwave method than the conventional synthesis. The T g 's of the nanocomposites using acid and amine functionalized MWCNTs are greater than 300 C, in both methods. This is attributed to the presence of hydrogen bond and strong covalent bond in both the acid-MWCNT/polyimide and amine-MWCNT/polyimide systems. The morphological studies of the nanocomposites synthesized using microwave irradiation show that a distinct MWCNT nanofibrillar network is formed in the matrix when MWCNT or acid-MWCNT is used. A homogeneous morphology, without distinct nanotube domains is seen when the amine-MWCNT is covalently linked to the polymer. POLYM. COMPOS., 37:2417-2424, 2016

␥-Fe 2 O 3 polystyrene (PS) composite films were prepared by a gel-casting technique to obtain monodisperse composite films. To understand the effect of additives on the prepared composite films, additives such as rice husk ash and thiourea were made to disperse into the PS matrix. The as-prepared ␥-Fe 2 O 3 PS composite films, along with their additives, were subjected to characterization and study by X-ray diffraction, scanning electron microscopy, thermal, IR, and dielectric measurement techniques. These studies showed monodisperse and chemically homogenous composite films with an increase in thermal behavior. An interesting self-assembly of rod-like nanoparticles of ␥-Fe 2 O 3 particles into the polymer matrix, which formed spherical packets, was observed for the ␥-Fe 2 O 3 PS composite film. The electrical behavior of these films was interesting, as some showed conduction whereas others showed an increase in dielectric behavior. This nature was explained by the dielectric measurements.

␥-Fe 2 O 3 -high-density polyethylene (HDPE) composite films are prepared by a gel-casting technique. To understand the effect of additives, rice husk ash and thiourea are made to disperse in the HDPE matrix to obtain the composite films with additives. The as-prepared ␥-Fe 2 O 3 -HDPE composite films with their additives are subjected to characterization and study through X-ray diffraction, thermal, scanning electron microscopy, and dielectric measurements. The results are qualitatively treated.