Polyimide–Organosilicate Hybrids with Improved Thermal and Optical Properties

Through hydrolysis and polycondensation of amino-silane with alkyl bridged silane, a new type of polysilsesquioxane (PSSQ) was obtained. Here we use amine functionalized silane and bis­(silyl)­ethane to synthesize alkyl chain linked PSSQ. Compared to conventional polyhedral oligomeric silsesquioxane (POSS), this new silane compound has both enhanced thermal stability and improved compatibility with poly­(amic acid). Gelation of this silane compound with poly­(amic acid) provides polyimide–organosilicate composite materials. We show that films made from solutions of the composites exhibit higher optical transparency and superior dimensional stability during thermal treatment than films of pure polyimide or of polyimide composites with conventional POSS. Bridging of POSS and chemical bonding between POSS and polyimide chains significantly enhance the physical properties. These results provide useful information for designing molecular architecture for the fabrication of high-performance plastic substrates in the future display devices

Induced Infiltration of Hole-Transporting Polymer into Photocatalyst for Staunch Polymer–Metal Oxide Hybrid Solar Cells

For efficient solar cells based on organic semiconductors, a good mixture of photoactive materials in the bulk heterojunction on the length scale of several tens of nanometers is an important requirement to prevent exciton recombination. Herein, we demonstrate that nanoporous titanium dioxide inverse opal structures fabricated using a self-assembled monolayer method and with enhanced infiltration of electron-donating polymers is an efficient electron-extracting layer, which enhances the photovoltaic performance. A calcination process generates an inverse opal structure of titanium dioxide (<70 nm of pore diameters) providing three-dimensional (3D) electron transport pathways. Hole-transporting polymers was successfully infiltrated into the pores of the surface-modified titanium dioxide under vacuum conditions at 200 °C. The resulting geometry expands the interfacial area between hole- and electron-transport materials, increasing the thickness of the active layer. The controlled polymer-coating process over titanium dioxide materials enhanced photocurrent of the solar cell device. Density functional theory calculations show improved interfacial adhesion between the self-assembled monolayer-modified surface and polymer molecules, supporting the experimental result of enhanced polymer infiltration into the voids. These results suggest that the 3D inverse opal structure of the surface-modified titanium dioxide can serve as a favorable electron-extracting layer in further enhancing optoelectronic performance based on organic or organic–inorganic hybrid solar cell

Enhanced Electrochemical Stability of a Zwitterionic-Polymer-Functionalized Electrode for Capacitive Deionization

In capacitive deionization, the salt-adsorption capacity of the electrode is critical for the efficient softening of brackish water. To improve the water-deionization capacity, the carbon electrode surface is modified with ion-exchange resins. Herein, we introduce the encapsulation of zwitterionic polymers over activated carbon to provide a resistant barrier that stabilizes the structure of electrode during electrochemical performance and enhances the capacitive deionization efficiency. Compared to conventional activated carbon, the surface-modified activated carbon exhibits significantly enhanced capacitive deionization, with a salt adsorption capacity of ∼2.0 × 10^–4 mg/mL and a minimum conductivity of ∼43 μS/cm in the alkali-metal ions solution. Encapsulating the activated-carbon surface increased the number of ions adsorption sites and the surface area of the electrode, which improved the charge separation and deionization efficiency. In addition, the coating layer suppresses side reactions between the electrode and electrolyte, thus providing a stable cyclability. Our experimental findings suggest that the well-distributed coating layer leads to a synergistic effect on the enhanced electrochemical performance. In addition, density functional theory calculation reveals that a favorable binding affinity exists between the alkali-metal ion and zwitterionic polymer, which supports the preferable salt ions adsorption on the coating layer. The results provide useful information for designing more efficient capacitive-deionization electrodes that require high electrochemical stability