Organic–inorganic polymer hybrids and porous materials obtained on their basis

Tetramethoxysilane (TMOS) or tetraethoxysilane (TEOS), an organic monomer [methylmethacrylate (MMA) or styrene (St)] and either α‐propylmethacryloxy‐ω‐trimethylsiloxy‐oligo(dimethylsiloxane) (OMS), as a compatibilizing agent, or α,ω‐bis(vinyl) oligo(dimethylsiloxane) (OVS), as compatibilizing and crosslinking agent, were allowed to undergo a sol–gel reaction under acidic condition and in the presence of 2,2′‐azoisobutyronitrile (AIBN) as a free‐radical initiator. The hydrolysis‐condensation and in situ free‐radical polymerization occur independently, to give a hybrid consisting of both inorganic and organic components. The conversion of the monomers to the proper polymers was monitored by IR spectroscopy and TGA. The resistance of the organic polymers to solvent extraction was also studied. The hybrids were pyrolyzed in an oxidative atmosphere. By decomposition, the organic polymer generated pores in the inorganic matrix. A quantitative evaluation of the characteristics for the resulting porous material was made by determination of the specific area, pore volume, and average radius. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2060–2067, 2003     

Design, fabrication and characterization of indefinite metamaterials of nanowires

Indefinite optical properties, which are typically characterized by hyperbolic dispersion relations, have not been observed in naturally occurring materials, but can be realized through a metamaterial approach. We present here the design, fabrication and characterization of nanowire metamaterials with indefinite permittivity, in which all-angle negative refraction of light is observed. The bottom-up fabrication technique, which applies electrochemical plating of nanowires in porous alumina template, is developed and demonstrated in achieving uniform hyperbolic optical properties at a large scale. We developed techniques to improve the uniformity and to reduce the defect density in the sample. The non-magnetic design and the off-resonance operation of the nanowire metamaterials significantly reduce the energy loss of electromagnetic waves and make the broad-band negative refraction of light possible.     

Simultaneous in situ monitoring of acrylic acid polymerization reaction on N-carboxymethyl chitosan using multidetectors: Formation of a new bioadhesive and gastroprotective hybrid particle

Chitosan and polyacrylic acid (PAA) both have weak, short-lasting bioadhesive properties; therefore, a hybrid particle composed of a chitosan derivative and PAA could be used as a new bioadhesive agent. Using simultaneous in-situ monitoring with a multidetection system, N-carboxymethyl chitosan was ionically bonded to acrylic acid and then polymerized using potassium persulphate as the initiator (N-CMC_A-D_h of 165 nm). The PAA on N-CMC_A was crosslinked using N,N-methylene-bisacrylamide (N-CMC_AC-D_h of 141 nm). During polymerization, the solution developed a milky white appearance, and polymerization kinetics was determined to be 3.2 × 10^−3 ± 4.0 × 10⁻⁶ mmol/min. The reaction for PAA alone was 1.7 times faster than that of the hybrid system. The particles showed an increase in thermal stability and reduction of thermal-mass loss compared with the N-CMC alone. The N-CMC_AC particles showed the highest bioadhesion onto the stomach. The gastroprotection index of N-CMCh_AC particles against ethanol/HCl-induced ulcers in mice was 68.2 ± 6.4%. Similar results were observed for omeprazole (74.2 ± 5.3%). The particles obtained in this work have potential for use in drug delivery to the stomach, perhaps to aid in treating ulceration and inflammation, and can be used as a system for the prevention of ethanol-induced ulcers.     

Experimental Strategy and Mechanistic View to Boost the Photocatalytic Activity of Cs3Bi2Br9 Lead-Free Perovskite Derivative by g-C3N4 Composite Engineering

The rational design of heterojunctions based on metal halide perovskites (MHPs) is an effective route to create novel photocatalysts to run relevant solar-driven reactions. In this work, an experimental and computational study on the synergic coupling between a lead-free Cs₃Bi₂Br₉ perovskite derivative and g-C₃N₄ is presented. A relevant boost of the hydrogen photogeneration by more than one order of magnitude is recorded when going from pure g-C₃N₄ to the Cs₃Bi₂Br₉/g-C₃N₄ system. Effective catalytic activity is also achieved in the degradation of the organic pollutant with methylene blue as a model molecule. Based upon complementary experimental outputs and advanced computational modeling, a rationale is provided to understand the heterojunction functionality as well as the trend of hydrogen production as a function of perovskite loading. This work adds further solid evidence for the possible application of MHPs in photocatalysis, which is emerging as an extremely appealing and promising field of application of these superior semiconductors.     

Positive‐tone,aqueous‐developable,polynorbornene dielectric: Lithographic,and dissolution properties

A positive‐tone, aqueous base soluble, polynorbornene (PNB) dielectric formulation has been developed. The photolithographic solubility switching mechanism is based on diazonaphthoquinone (DNQ) inhibition of PNB resin functionalized with pendent fluoroalcohol and carboxylic acid substituents. The optical contrast (at 365 nm) was found to be 2.3. The maximum height‐to‐width aspect ratio of developed line and space features was 3 : 2. The sensitivity, D₁₀₀, of a formulation containing 20 pphr of DNQ photoactive compound (PAC) was calculated to be 408 mJ cm^?2. The effects of the PAC molecule structure on miscibility and dissolution of the photosensitive films in aqueous base developer were studied. The effect of the monomer composition of the PNB polymer on the dissolution rate of the formulated PNB resin was evaluated. A unique dissolution and swelling behavior was observed. The effect is attributed to a copolymer synthesized with two monomers each of which is susceptible to deprotonation in aqueous base. FTIR measurements showed that the pure PNBFA has a small percentage of free hydroxyl groups, which did not change appreciably by the addition of PAC to the mixture. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Complex amplitude correlation for compensation of large in-plane motion in digital speckle pattern interferometry

The use of complex amplitude correlation to compensate for large in-plane motion in digital speckle pattern interferometry is investigated. The result is compared with experiments where digital speckle photography (DSP) is used for compensation. An advantage of using complex amplitude correlation instead of intensity correlation (as in DSP) is that the phase change describing the deformation is retrieved directly from the correlation peak, and there is no need to compensate for the large movement and then use the interferometric algorithms. A discovered drawback of this method is that the correlation values drop quickly if a phase gradient larger than pi is present in the subimages used for cross correlation. This means that, for the complex amplitude correlation to be used, the size of the subimages must be well chosen or a third par?meter in the cross-correlation algorithm that compensates for the phase variation is needed. Correlation values and wrapped phase maps from the two techniques (intensity and complex amplitude correlation) are presented.     

Adapting traditional software processes to virtual environments development

Virtual environments (VEs) are special kinds of interactive systems currently used in many fields such as education, training and medicine. However, as VE development is relatively recent, there is little experience in the area. Software engineering, the discipline which assures quality software, has not been successfully applied to date. In developing VEs, the object‐oriented software engineering paradigm is the most suitable even though principles and techniques are insufficient. In this paper, we will demonstrate this inadequacy through the development of two different VEs, identify the processes to be improved, offer a set of guidelines to improve them (coined SENDA), and present the results obtained with SENDA. Copyright © 2003 John Wiley & Sons, Ltd.     

In-plane dynamic speckle interferometry: comparison between a combined speckle interferometry/speckle correlation and an update of the reference image

A common problem during study of, for instance, tensile tests with interferometers is that the sample moves too much so that the speckles decorrelate and no phase information is obtained. Two ways to overcome this problem are compared: a combination of speckle interferometry and speckle correlation and a method in which the reference image is updated during the experiment. The comparison shows that both techniques can be used to measure the deformation of an object even if it is exposed to rigid body motions. Both techniques are applied to measurements of microscale deformation fields of an adhesive joint in a carbon-fiber epoxy composite.