Polynorbornene/fluorosilica hybrids for hydrophobic and oleophobic coatings

Polynorbornene dicarboxylic anhydride (PNA)/fluorosilica hybrid coating materials with good hydrophobicity, oleophobicity, transparency, thermal stability, and hardness were synthesised using a sol–gel method. The surface structure, transparency, hydrophobicity, oleophobicity, and surface free energy of the coating could be controlled by adjusting the fluorosilane ratio. The maximum static water and oil contact angles of films were 112° and 87°, respectively. The PNA/fluorosilica hybrid films exhibited good transparency and colourlessness. The marks written using water and oil-based pens on the films could be erased with a tissue even after eight times. In addition, the hardness of the hybrid films was enhanced to 4H with increasing fluorosilane content.     

Recent progress in smart polymer composite particles in electric and magnetic fields

Electrorheological (ER) and magnetorheological (MR) fluids based on electro‐ and magneto‐responsive particles, respectively, are smart suspensions with the ability to undergo phase transitions from a liquid‐like to a solid‐like state as a result of stimuli of an electric or magnetic field. The application of polymer composite materials rather than pure polymeric or inorganic materials is aiming to solve the problems in the use of both ER and MR materials, such as low activity, physical and chemical stability, and production cost. Various fabrication methods of polymer composite materials with electro‐activity or magneto‐activity developed and effectively applied in this field to boost the wide commercialization of both ER and MR fluids are briefly reviewed in this perspective. © 2012 Society of Chemical Industry     

Piezoresistive effects of copper-filled polydimethylsiloxane composites near critical pressure

Piezoresistive properties of polydimethylsiloxane (PDMS) filled with copper particles in volume fraction above the electrical percolation threshold (25.3–50.7 vol%) were investigated. Piezoresistive behavior of the PDMS-copper composites under compressive pressure showed not only a change in resistance by approximately six orders of magnitude (∼1.5 MPa), but also a change in the critical pressure due to variations in the hardness of the composites. Resistivity relaxation was observed near the critical pressure and was explained through a stress relaxation and percolation mechanism. The mean tunneling distance was calculated by using a theoretical equation for percolation under compression. When the gauge factors of the composites were plotted versus strain, a universal curve was obtained regardless of the copper contents. Finally, the PDMS-copper composite demonstrated good repeatability, showing only small differences in the relative resistance after five successive tests.     

Protein nanopatterns and biosensors using gold binding polypeptide as a fusion partner

An efficient strategy for immobilizing proteins on a gold surface was developed by employing the gold binding polypeptide (GBP) as a fusion partner. Using the enhanced green fluorescent protein (EGFP), severe acute respiratory syndrome coronavirus (SARS-CoV) envelope protein (SCVme), and core streptavidin (cSA) of Streptomyces avidinii as model proteins, specific immobilization of the GBP-fusion proteins onto the gold nanoparticles and generation of protein nanopatterns on the bare gold surface were demonstrated. The GBP-fused SCVme bound to gold nanoparticles successfully interacted with its antibody and showed changes in absorbance and color, allowing efficient diagnosis of SARS-CoV. The fusion proteins could be successfully immobilized on the gold surface by nanopatterning and microcontact printing as examined by atomic force microscopy and surface plasmon resonance analysis. The poly(dimethylsiloxane) microfluidic channels were created on the gold surface and were used for antigen-antibody and DNA-DNA interaction studies. Specific immobilization of GBP-EGFP fusion protein and its interaction with the antibody in the microchannels could be demonstrated. By immobilizing the DNA probe through the use of GBP-fused cSA, specific hybridization of the target DNA prepared from Salmonella could also be achieved. The GBP-fusion method allows immobilization of proteins onto the gold surface without surface modification and in bioactive forms suitable for studying protein-protein, DNA-DNA, and other biomolecular interaction studies. Furthermore, these studies can be carried out in a microfluidic system, which allows high-throughput analysis of biomolecular interactions.     

Population balance modeling for a continuous gas phase olefin polymerization reactor

Steady-state population balance models have been developed for a continuous flow gas phase olefin polymerization process with both uniform sized and log-normally size distributed high activity catalyst feeds. For the calculation of polymer properties such as molecular weight averages and weight fraction of comonomers in the copolymer, a multigrain solid core model was used with an assumption that intraparticle monomer mass transfer resistance is negligibly small. The multigrain solid core model was incorporated into the population balance model and the effects of feed catalyst particle size distribution and catalyst deactivation parameters on the polymer production rate, polymer particle size distribution, and polymer properties were investigated. It is observed for deactivating catalyst that the polymer particle size distribution tends to be narrower with a reduced amount of large polymer particles. For the catalyst with nonuniform site deactivation, polymer particles of different sizes exhibit different molecular weight and copolymer composition. © 1994 John Wiley & Sons, Inc.     

Thermodynamic investigation of methanol and dimethyl ether synthesis from CO2 Hydrogenation

The thermodynamics involved in the catalytic hydrogenation of CO₂ have been examined extensively. By assuming that methanol and dimethyl ether (DME) are the main products, two reaction systems each consisting of two pararell reactions were analyzed and compared in terms of the equilibrium yield and selectivity of the useful products, methanol and DME. The calculation results demonstrated that the production of DME allows much higher oxygenate yield and selectivity than that of methanol.