Synthesis and characterization of side-chain poly(methacrylate)s bearing new azo-moieties

New side-chain poly(methacrylate)s with azo moieties were prepared by free radical copolymerization, starting from methyl methacrylate (MMA) and some original azo-monomers. The chromophore content was evaluated from ¹H-NMR spectroscopy and elemental analyses; all structures exhibited a high content of azobenzene units. UV–Vis measurements have also supported this fact. Reactivity ratios for the methacrylate systems and their corresponding Q–e values were calculated based on several initial feed compositions (MMA and the newly synthesized azo-monomers) using an integral method with its appropriate software. The polymers were also characterized by FTIR, SEC and DSC-TGA techniques. The coloured poly(methacrylate)s exhibited glass transition temperatures between 141 and 168 °C and thermal stabilities up to 306 °C.     

Effect of cinnamate comonomers on the dental formulation properties

This study reports the synthesis and characterization of two urethane dimethacrylates containing poly(ethylene oxide) or poly(propylene oxide) segment and cinnamate pendant moieties to be formulated in dental resin composites. ¹H NMR, ¹³C NMR, and Fourier transform infrared spectroscopies, gel permeation chromatography, electrospray ionization‐mass spectroscopy, and thermogravimetric measurements confirmed their structure, whereas the photopolymerization evolution of oligodimethacrylates relating to a low–molecular‐weight dicinnamate methacrylate under ultraviolet irradiation was investigated by photo‐differential scanning calorimeter, monitoring the degree of conversion (DC) and polymerization rate. The photopolymerization results reveal that the investigated derivatives display a good photoreactivity (DC: ～ 70%) during the formation of crosslinked polymers, the DC depending especially on the sample viscosity. The polymerization shrinkage for several mixtures including the urethane oligocinnamates (20 wt %) and diglycidyl methacrylate of bisphenol A/triethyleneglycol dimethacrylate system in the absence of filler was determined, the obtained values being in the range of 6.1–8.2 vol %. For few cured specimens incorporating quartz filler (75 wt %), water sorption/solubility, contact angle, and mechanical parameters were measured to establish if such monomers could be of interest in dentistry. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Atmospheric pressure plasma enhanced synthesis of flame retardant cellulosic materials

Flame retardant cellulosic materials have been produced using a silicon dioxide (SiO₂) network coating. SiO₂ network armor was prepared through hydrolysis and condensation of the precursor tetraethyl orthosilicate (TEOS), prior coating the substrates, and was cross linked on the surface of the substrates using atmospheric pressure plasma (APP) technique. Because of protection effects of the SiO₂ network armor, the cellulosic based fibers exhibit enhanced thermal properties (characterized by TGA and DSC) and improved flame retardant (proven by ASTM D1230‐99). Furthermore, the surface analysis (XPS and SEM) confirmed the presence of the SiO₂ network attached to the substrates even after intense ultrasound washes. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Screening of Molecular Virulence Markers in Staphylococcus aureus and Pseudomonas aeruginosa Strains Isolated from Clinical Infections

Staphylococcus (S.) aureus and Pseudomonas (Ps.) aeruginosa are two of the most frequently opportunistic pathogens isolated in nosocomial infections, responsible for severe infections in immunocompromised hosts. The frequent emergence of antibiotic-resistant S. aureus and Ps. aeruginosa strains has determined the development of new strategies in order to elucidate the different mechanisms used by these bacteria at different stages of the infectious process, providing the scientists with new procedures for preventing, or at least improving, the control of S. aureus and Ps. aeruginosa infections. The purpose of this study was to characterize the molecular markers of virulence in S. aureus and Ps. aeruginosa strains isolated from different clinical specimens. We used multiplex and uniplex PCR assays to detect the genes encoding different cell-wall associated and extracellular virulence factors, in order to evaluate potential associations between the presence of putative virulence genes and the outcome of infections caused by these bacteria. Our results demonstrate that all the studied S. aureus and Ps. aeruginosa strains synthesize the majority of the investigated virulence determinants, probably responsible for different types of infections.     

Large-scale optical-field measurements with geometric fibre constructs

Optical fields are measured using sequential arrangements of optical components such as lenses, filters, and beam splitters in conjunction with planar arrays of point detectors placed on a common axis. All such systems are constrained in terms of size, weight, durability and field of view. Here a new, geometric approach to optical-field measurements is presented that lifts some of the aforementioned limitations and, moreover, enables access to optical information on unprecedented length and volume scales. Tough polymeric photodetecting fibres drawn from a preform are woven into light-weight, low-optical-density, two- and three-dimensional constructs that measure the amplitude and phase of an electromagnetic field on very large areas. First, a three-dimensional spherical construct is used to measure the direction of illumination over 4pi steradians. Second, an intensity distribution is measured by a planar array using a tomographic algorithm. Finally, both the amplitude and phase of an optical wave front are acquired with a dual-plane construct. Hence, the problem of optical-field measurement is transformed from one involving the choice and placement of lenses and detector arrays to that of designing geometrical constructions of polymeric, light-sensitive fibres.     

Depletion-All-Around Operation of the SOI Four-Gate Transistor

In the silicon-on-insulator four-gate transistors (G⁴-FETs), the conducting channel can be surrounded by depletion regions induced by independent vertical metal-oxide-semiconductor gates and lateral JFET gates. This unique conduction mechanism named depletion-all-around (DAA) enables majority carriers to flow in the volume of the silicon film far from the silicon/oxide interfaces. Especially when the interfaces are driven to inversion, the control of the lateral JFET gates on the conduction is maximized, while the sensitivity of the volume channel to the oxide and interface defects is minimized. This leads to excellent analog performance, low noise, and reduced sensitivity to ionizing radiation. The G⁴-FET properties in DAA mode are presented from multiple perspectives: experimental results, 3-D device simulations, and analytical modeling