Photoinitiated cationic polymerization using a novel phenacyl anilinium salt

A novel phenacyl anilinium salt, N-phenacyl, N,N-dimethylanilinium hexafluoroantimonate, (PDA), has been synthesized and used as photoinitiator for cationic polymerization of cyclohexene oxide (CHO), butyl vinyl ether (BVE) and N-vinyl carbazol (NVC). Plausible mechanism of the photoinitiation involves the decay of the excited PDA with both heterolytic and homolytic cleavages of carbon-nitrogen bond. Thus, phenacylium cations formed directly or subsequent intermolecular electron transfer, respectively, initiate the polymerization.     

Flocculation of coal suspension with mono/dual polymer systems and contribution of Ca(II)/Mg(II) ions

In the experimental study carried out on mono-flocculation, anionic and especially non-ionic polymers strongly flocculated the coal suspension than cationic polymer. The dual-flocculation of the coal suspension with cationic and anionic polymer combination was also studied and the high performances of flocculation were also reached with dual-polymer approach. Furthermore, dual-polymer system required lower concentrations for the successful flocculation of coal particles. On the other hand, the pre-destabilization of the coal suspension with calcium and magnesium ions at particular pH and concentrations highly improved the flocculation of fine coal particles with these polymers.     

Changes in lipid content and composition during germination of groundnuts

The cotyledons of two varieties of germinating groundnut seeds (Runner and Bunch) were analysed periodically for their lipid content and fatty acid composition over a period of 132 h. The lipid content decreased drastically during germination. More drastic changes in lipid constituents were observed for light-grown seedlings than for dark-grown ones. In general, the non-polar lipids (NPL) were metabolised faster than the polar ones (P > 0.05) especially in those seeds grown in the dark. The rate of decrease in NPL content almost paralleled that of increase in glycolipid (GL) content. Triacyl glycerol content decreased noticeably during germination while other NPL tended to increase. Among the GL, sterylglucoside increased rapidly during early germination under darkness, only to decrease steadily thereafter. A converse effect was observed for acyl sterylglucoside which, in the dark, decreased rapidly at early germination only to increase equally rapidly later on. Among the phospholipids (PL), only phosphatidic acid showed a marked increase during germination, under both growth conditions, while others tended to decrease in varying degrees. The changing patterns of GL and PL during germination seem to follow the pattern of the formation of photosynthetic tissues and the metabolic conversion of PL. The major fatty acids of the three lipid groups, which more or less decreased or increased in varying degrees with germination in light-grown seeds were oleic, linoleic, palmitic, stearic, arachidic and lignoceric acids in decreasing order of prominence at early germination.     

Reflex sympathetic dystrophy syndrome due to arteriovenous fistula

A patient with end-stage renal disease presented with reflex sympathetic dystrophy syndrome (RSDS) on her left hand 1 month after arteriovenous fistula (AVF) surgery. Magnetic resonance angiography revealed steal syndrome at the AVF level. Bone scintigraphy revealed early-stage RSDS. We considered that arterial insufficiency because of steal phenomenon following AVF surgery and underlying occlusive arterial disease triggered RSDS development.     

Polymeric N‐allyl vinylpyridinium salts as addition–fragmentation type initiators for cationic polymerization

Polymeric allyl pyridinium salts were synthesized from styrene and 4‐vinyl pyridine copolymers by quaternization and counteranion exchange reactions. The initiation capability of these copolymers, in conjunction with a photochemical free radical source such as benzoin, via an addition –fragmentation mechanism in the cationic polymerization of cyclohexene oxide is investigated. © 2001 Society of Chemical Industry     

Fluidic assembly at the microscale: progress and prospects

Assembly permits the integration of different materials and manufacturing processes to increase system functionality. It is an essential step in the fabrication of useful systems across size scales from buildings to molecules. However, at the microscale, traditional “grasp and release” assembly methods and chemically inspired self-assembly processes are less effective due to scaling effects. Many methods have been developed for improving microscale assembly. Often these methods include fluidic forces or the use a fluidic medium in order to enhance their performance. This paper reviews basic assembly theory and modeling methods. Three basic assembly strategies (tool-directed, process-directed, and part-directed) are proposed for categorizing these methods. It then summarizes progress in using fluidic forces (surface tension, viscous) and external fields (magnetic, electric, light) to aid microscale assembly. Applications of recent advances in both continuous flow and digital microfluidics in microscale assembly are also addressed.     

Thermal and mechanical properties of polypropylene nanocomposite materials reinforced with cellulose nano whiskers

We use polypropylene (PP, an apolar polymer) and cellulose nano whiskers (CNW, a polar material) to produce nano polymer composites with enhanced mechanical and thermal properties. To improve compatibility, maleic anhydride grafted PP has also been used as a coupling agent. To enhance the uniform distribution of CNW in the composite, the matrix polymer is dissolved in toluene, and sonification and magnetic stirring are applied. Good film transparency indicates uniform CNW dispersion, but CNW domains in the composite film observed under an scanning electron microscope may indicate slight agglomeration of CNW in the composite film. The tensile strength of the composite compared with neat PP improves by 70–80% with the addition of CNW. The crystallinity has also been improved by about 50% in the CNW reinforced samples. As the content of CNW increases, the composite exhibits higher thermal degradation temperature, higher hydrophilicity, and higher thermal conductivity. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synthesis of triglyceride-based urethane macromers and their use in copolymerization

Triglyceride oil-based urethane macromer (TGU) containing vinyl double bond was synthesized by the reaction of partial glyceride mixture (PGM) and methyl vinyl isocyanate (MVI). Free radical polymerization and copolymerization of TGU was studied. The structure of the TGU and polymers were elucidated by gel permeation chromatography (GPC) analysis, Fourier transform infrared spectroscopy (FT-IR) and ¹H nuclear magnetic resonance (¹H NMR) spectral measurements. The film properties of polymers were investigated by water resistance, alkali and acid resistance and contact angle measurements.     

Thermal stresses on membrane based microdevices

We developed a closed form analytical solution for thermal stresses on membrane based “released” MEMS devices. As all the layers forming the membrane has thicknesses close to one another, the assumption of having thick substrate fails. We employed stress superposition principles to obtain the intrinsic stresses caused by coefficient of thermal expansion (CTE) mismatch of the membrane layers. We also accounted for the membrane release. We illustrated that for a bilayer strip consisting of a thin film on a thick substrate, our formulation simplifies to the well-known Stoney equation. The results indicate that the thermal stress can be minimized by the appropriate choice of dielectric materials, metal electrode selections and deposition tools. Replacing the silicon nitride (Si₃N₄) layer deposited by low pressure chemical vapor deposition (LPCVD) with a silicon oxide (SiO₂) layer deposited by plasma enhanced chemical vapor deposition (PEVCD) reduces the average thermal stress by 93%.