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Absorption Behavior (absorption + behavior)
Selected AbstractsSilicon-Based Near-Visible Logpile Photonic CrystalADVANCED MATERIALS, Issue 37 2010Ganapathi Subramania A nanocavity structure is embedded inside a silicon logpile photonic crystal that demonstrates tunable absorption behavior at near visible wavelengths well beyond the absorption edge of silicon. This is due to silicon's indirect bandgap resulting in a relatively slow increase in the absorption of silicon with decreasing wavelength. Our results open up the possibility of utilizing the wide, complete three dimensional photonic gap enabled by the large refractive index of silicon to create three dimensional photonic crystal based devices well into the visible regime. [source] Organometallic Complexes for Nonlinear Optics.ADVANCED MATERIALS, Issue 22 2009An alkynylruthenium dendrimer exhibits two-photon absorption behavior below 1000,nm, and a nonlinear increase in nonlinearity upon dendrimer growth. Beyond 1000,nm, it undergoes 3PA-induced photochemistry. Its nonlinear optical performance is an order of magnitude greater than that of similar organic dendrimers, demonstrating the performance enhancement possible upon incorporation of metal centers into a molecular architecture. [source] Moisture absorption behavior of epoxies and their S2 glass compositesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2008Amit Chatterjee Abstract The influence of moisture exposure on the behavior of three toughened epoxy,amine systems (scrimp resins SC11, SC15, and SC79, Applied Poleramic, Inc., Benicia, CA) was investigated. Neat resin samples were conditioned by immersion in distilled water at 71°C and in an environmental chamber at 85% relative humidity and 87.8°C until saturation. The equilibrium weight gain ranged from 1.8 to 3.8% for the resins. The long-chain, low-crosslink-density epoxy system (SC11) absorbed the highest amount of water and was saturated first, and it was followed by the medium-crosslink-density (SC15) and high-crosslink-density materials (SC79). The moisture diffusivity decreased with the increasing crosslink density of the resins. The percentage reduction of the glass-transition temperature (Tg) at equilibrium moisture absorption was highest for the low-crosslink molecule. The percentage reductions for the medium-crosslink and higher crosslink systems were comparable. A net weight loss after drying was observed for the SC11 and SC79 resin systems. Fourier transform infrared analysis confirmed the segment breakage and leaching of molecules from the epoxy,amine network. The effects of moisture cycling on Tg were dependent on the epoxy,amine morphology. During the drying stage, Tg increased to a value higher than that of the unaged dry systems. The S2 glass composite samples were conditioned under identical conditions for the resin system. Composite systems absorbed less moisture than the neat resins as expected. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008 [source] New Photocleavable Structures, 4,MACROMOLECULAR RAPID COMMUNICATIONS, Issue 1 2008Acylgermane-Based Photoinitiator for Visible Light Curing Abstract As highly reactive acylphosphine oxide-based photoinitiators (PIs) are limited in the application for dental materials by their absorption behavior, we were interested to prepare acylgermane 1. UV-Vis absorption maximum of the important n,,* transition was red shifted about 30 nm compared to monoacylphosphine oxides. Photo-DSC results with a dental LED lamp showed nearly the same reactivity for 1 compared to camphorquinone (CQ), while monoacylphosphine oxides are not reactive. In broadband irradiation experiments, significantly higher reactivity compared to CQ was found. Application-oriented tests showed sufficient storage stability of the formulation and excellent photobleaching behavior. [source] Water absorption behavior of different types of organophilic montmorillonite-filled polyamide 6/polypropylene nanocompositesPOLYMER COMPOSITES, Issue 2 2010Kusmono The water absorption behavior of different types of organophilic montmorillonite (OMMT)-filled polyamide 6/polypropylene nanocomposites with and without compatibilizers (maleated PP or PP- g -MA and maleated styrene-ethylene/butylene-styrene or SEBS- g -MA) was evaluated. Four different types of OMMT, i.e., dodecylamine-modified MMT (D-MMT), 12 aminolauric acid-modified MMT (A-MMT), stearylamine-modified MMT (S-MMT), and commercial organo-MMT (C-MMT) were used as reinforcement. The water absorption response of the nanocomposites was studied and analyzed by tensile test and morphology assessment by scanning electron microscopy (SEM). The kinetics of water absorption of the nanocomposites conforms to Fick's law. The Mm and D are dependent on the types of OMMT and compatibilizers. The equilibrium water content and diffusivity of PA6/PP blend were increased by the addition of OMMT but decreased in the presence of compatibilizers. On water absorption, both strength and stiffness of the nanocomposites were drastically decreased, but the ductility was remarkably increased. Both PP- g -MA and SEBS- g -MA played an effective role as compatibilizers for the nanocomposites. This was manifested by their higher retention ability in strength and stiffness (in the wet and re-dried states), reduced the equilibrium water content, and diffusivity of the nanocomposites. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers [source] Enzyme immobilization on ultrafine cellulose fibers via poly(acrylic acid) electrolyte graftsBIOTECHNOLOGY & BIOENGINEERING, Issue 4 2005Hong Chen Abstract Ultrafine cellulose fiber (diameter 200,400 nm) surfaces were grafted with polyacrylic acid (PAA) via either ceric ion initiated polymerization or methacrylation of cellulose with methacrylate chloride (MACl) and subsequent free-radical polymerization of acrylic acid. PAA grafts by ceric ion initiated polymerization increased with increasing reaction time (2,24 h), monomer (0.3,2.4 M), and initiator (1,10 mM) concentrations, and spanned a broad range from 5.5,850%. PAA grafts on the methacrylated cellulose fibers also increased with increasing molar ratios of MACl to cellulosic hydroxyl groups (MACl/OH, 2,6.4) and monomer acrylic acid (AA) to initiator potassium persulfate (KPS) ratios ([AA]/[KPS], 1.5,6), and were in a much narrower range between 12.8% and 29.4%. The adsorption of lipase (at 1 mg/ml lipase and pH 7) and the activity of adsorbed lipase (pH 8.5, 30°C), in both cases decreased with increasing PAA grafts. The highest adsorption and activity of the lipase on the ceric ion initiated grafted fibers were 1.28 g/g PAA and 4.3 U/mg lipase, respectively, at the lowest grafting level of 5.5% PAA, whereas they were 0.33 g/g PAA and 7.1 U/mg lipase, respectively, at 12.8% PAA grafts on the methacrylated and grafted fibers. The properties of the grafted fibers and the absorption behavior and activity of lipase suggest that the PAA grafts are gel-like by ceric-initiated reaction and brush-like by methacrylation and polymerization. The adsorbed lipase on the ceric ion-initiated grafted surface possessed greatly improved organic solvent stability over the crude lipase. The adsorbed lipases exhibited 0.5 and 0.3 of the initial activity in the second and third assay cycles, respectively. © 2004 Wiley Periodicals, Inc. [source] Facile syntheses, morphologies, and optical absorptions of P3HT coil-rod-coil triblock copolymersJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 15 2010Herman Lim Abstract Here we report syntheses, photophysical properties, and morphologies of a series of coil-rod-coil ABA triblock copolymers containing highly regioregular poly(3-hexylthiophene) (P3HT) as the central rod block. A new methodology, based on the coupling reaction between living polymeric anions [polystyrene, polyisoprene, and poly(methyl methacrylate)] and aldehyde terminated P3HT, was successfully developed to synthesize the triblock copolymers with low polydispersities. This coupling reaction was effective for building blocks with a variety of molecular weights; therefore, a good variation in compositions of the triblock copolymers could be feasibly achieved. The non-P3HT coil segments and the solvents were found to exhibit noticeable effects on morphologies of the spin-coated thin films. Attachment of the coil segments to P3HT did not change the optical absorption of the P3HT segment as the block copolymers were dissolved in solution regardless the chemical structure and the molecular weight of the coil segment. Interestingly, different UV,vis absorption behaviors were observed for the spin-coated thin films of the block copolymers, which closely related to their morphologies. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3311,3322, 2010 [source] | ||||||||||