Porous Polyimide-Silica Composite: A New Thermal Resistant Flexible Material

ABSTRACTWe developed a new highly porous polyimide (PI) -silica composite with high flexibility, mechanical strength, and heat resistance. The composite was prepared by a new process consisting of (1) phase separation of a mixture of PI precursor (polyamic acid), solvent, and silicon alkoxide, induced by high-pressure CO2 (40 °C, 20 MPa), (2) silicate formation by sol-gel reaction, and (3) supercritical CO2 extraction of the solvent. The composite had a bimodal porous structure with micropores of 10-30 μm and nanopores of ∼50 nm. In the PI matrix, silica nanoparticles (< 100 nm in diameter) were highly dispersed. Porosity of the composite was 78%, which is higher than that of conventional porous PI prepared by physical foaming technique. Relative dielectric constant of the material was lower than 1.4 at 1 MHz. The porous PI-silica composite sheet was flexible enough to be folded without cracking. Notably, the Young’s modulus (0.80 GPa) and the onset decomposition temperature (600 °C) of the PI-silica composite were higher than those of conventional porous PI with similar porosity, respectively. The porous PI-silica composite is promising as a flexible thermal insulator for high-temperature use and as a thermal resistant low-k material.

NANOCOMPOSITE ELECTRODES CONSISTING OF 3DOM CARBON WITH BIMODAL POROUS STRUCTURE AND CONDUCTING POLYMERS FOR ELECTROCHEMICAL CAPACITORS

Three-dimensionally ordered macroporous (3DOM) carbon with mesoporous walls was prepared by the colloidal crystal templating method using polystyrene (PS) and silica particles. Colloidal crystals consisting of monodispersed PS sphere (204 nm diameter) and silica particles (4–6 nm) were carbonized in Ar , and the silica was removed by etching in HF, and then 3DOM carbon with bimodal pore structure was obtained. Conducting polymers of polyaniline (PAn) and polypyrrole (PPy) were electrochemically deposited on the internal surface of macropores in 3DOM carbons. The mesopores were not closed after the deposition of the polymers. The composites were utilized as electrodes for electrochemical capacitors. The specific capacitances of prepared carbon– PAn and carbon– PPy composites were found to be 237 and 152 F g-1, respectively. The incorporation of the conducting polymers dramatically increased the charge storage capacities of the 3DOM carbon electrodes.

New Generation of Hybrid Organic-Inorganic Macrocellular Foams: Integrative Chemistry Toward Reaching Multifunctional Materials

ABSTRACTThe elaboration of organosilica based hybrid monoliths exhibiting a hierarchically structured bimodal porous structure with tunable functionality have been processed via High Internal Polymeric Emulsion (HIPE) process for the first time. Through one pot synthesis, many organic functionalities that can act as network modifiers (Methyl, Dinitrophenylamino, Benzyl, Mercaptopropyl) or co-network formers (Pyrrol) have been anchored to the amorphous silica porous network. The resulting materials have been thoroughly characterized via a large set of techniques SEM, TEM, SAXS, mercury porosimmetry, nitrogen adsorption isotherms, FTIR, 29Si MAS NMR. These sol-gel derived hierarchical open cell functional hybrid monoliths exhibit macroscopic void spaces ranging from 5 up to 30 [.proportional]m and their accessible micro-mesoporosity, reveal hexagonal organisation for the dinitrophenylamino, benzyl, and pyrrol based hybrids. The average condensation degree for these hybrid networks ranges between 86 and 90% yielding shaped monoliths with both good integrity and sufficient mechanical properties to be usable as functional catalytic or chromatographic supports.