Synthesis and characterization of poly(keto-amines). 2. Self-polycondensation of 4-methyl-3-aminophenacyl chloride and 2-methyl-4-aminophenacyl chloride

Poly(keto-amines) such as poly(4-methyl-3-iminophenacyls) and poly(2-methyl-4-iminophenacyls) were prepared by self-polycondensation of 4-methyl-3-aminophenacyl chloride and 2-methyl-4-aminophenacyl chloride under different experimental conditions. All the polymer samples were insoluble in common organic solvents. They were characterized by elemental analysis, IR spectral studies, estimation of M?_n by non-aqueous conductometric titration and study of thermal properties by DTA. The properties of P4M3IP and P2M4IP were compared with those of poly(4-iminophenacyls).     

Colloidal Quantum Dot Infrared Lasers Featuring Sub-Single-Exciton Threshold and Very High Gain

The use of colloidal quantum dots (CQDs) as a gain medium in infrared laser devices has been underpinned by the need for high pumping intensities, very short gain lifetimes, and low gain coefficients. Here, PbS/PbSSe core/alloyed-shell CQDs are employed as an infrared gain medium that results in highly suppressed Auger recombination with a lifetime of 485 ps, lowering the amplified spontaneous emission (ASE) threshold down to 300 µJ cm⁻², and showing a record high net modal gain coefficient of 2180 cm⁻¹. By doping these engineered core/shell CQDs up to nearly filling the first excited state, a significant reduction of optical gain threshold is demonstrated, measured by transient absorption, to an average-exciton population-per-dot 〈N^th〉_g of 0.45 due to bleaching of the ground state absorption. This in turn have led to a fivefold reduction in ASE threshold at 〈N^th〉_ASE = 0.70 excitons-per-dot, associated with a gain lifetime of 280 ps. Finally, these heterostructured QDs are used to achieve near-infrared lasing at 1670 nm at a pump fluences corresponding to sub-single-exciton-per-dot threshold (〈N^th〉_Las = 0.87). This work brings infrared CQD lasing thresholds on par to their visible counterparts, and paves the way toward solution-processed infrared laser diodes.     

A pathway for net-zero energy buildings: creating a case for zero cost increase

To have market relevance and gain widespread market adoption, zero energy buildings (ZEBs) will need to be designed and constructed cost-effectively, and preferably without additional costs. An approach was developed to create low-energy buildings without additional construction costs such that it yielded innovation in building technology and integration by the market. A case study of the implementation of this method is presented to provide a data point that ZEBs can be built with zero cost increase. Documenting cost-control best practices and packaging those strategies for adoption by the commercial building sector will help make the business case for ZEBs for mainstream construction and promote market uptake of the innovative technologies and design approaches needed. The holistic implementation of cost-control strategies will enable ZEBs to be designed and constructed on a typical budget. The current state of ZEB economics is evaluated and a path forward is proposed for greater market penetration of ZEBs. By demonstrating how to combine ZEB technologies and design approaches into an overall efficiency package that can be implemented at minimal (zero, in certain cases) incremental capital cost, the domain of ZEB design and construction can be expanded from a niche market to the commercial construction mainstream.     

Studies on carboxy‐terminated liquid natural rubber in NBR

Maleic anhydride was chemically attached to depolymerized natural rubber by a photochemical reaction. The product Carboxy Terminated Liquid Natural Rubber (CTNR) was characterized by ¹H‐NMR, IR, GPC, and TGA. The efficiency and permanence of CTNR were compared with conventional plasticizers in NBR vulcanizates. This polymeric plasticizer was found to be less volatile and more resistant to oil extraction. The vulcanizates showed improved aging resistance compared to vulcanizates containing conventional plasticizers. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 261–267, 2002; DOI 10.1002/app.10322     

Composition of clove (Syzygium aromaticum) bud oil extracted using carbon dioxide

Analysis of clove (Syzygium aromaticum L) bud oil extracted with liquid and supercritical carbon dioxide shows significant qualitative and quantitative compositional differences compared with oil obtained by the conventional hydrodistillation process. The parameters of pressure, temperature, contact time etc, and also the clove oil components, affect the extraction of the bud flavour from the spice.     

Studies on natural rubber bound para-phenylenediamine antioxidants in NBR

Para-phenylenediamine (PD) was chemically attached to depolymerized natural rubber by a photochemical reaction. The rubber bound PD was characterized by TLC, ¹H-NMR, IR, and TGA. The efficiency and permanence of the bound PD were compared with conventional antioxidants in NBR vulcanizates. The rubber bound PD was found to be less volatile and more resistant to water and oil extraction. The vulcanizates showed improved aging resistance in comparison to vulcanizates containing conventional antioxidants. The liquid rubber bound antioxidant reduces the amount of plasticizer required for compounding. © 1995 John Wiley & Sons, Inc.     

Differential scanning calorimetric investigation of curing of resins formed from furfural and various phenols

Curing reactions of adequately characterized phenol-furfural, o-chlorophenol-furfural, P-chlorophenol-furfural and p-tert-butyl phenol-furfural resins with hexamine were studied by differential scanning calorimetry. The data are analyzed by appropriate empirical relations with a view to examining their applicability to the present sets of data and to estimating kinetic parameters of the curing reactions.     

Synthesis and characterization of poly(keto-amines). 1. Self polycondensation of 4-aminophenacyl chloride

Novel poly(keto-amines), designated as poly(4-iminophenacyls) are prepared by self polycondensation of 4-aminophenacyl chloride under different experimental conditions. These polymers are insoluble in common solvents. The number average molecular weights of the polymer samples have been estimated by conductometric titration of a suspension of the polymer sample in formic acid against a standard perchloric acid. The polymer samples have been characterized by a comparative study of their IR spectra with those of the probable model compounds and by differential thermogravimetric analysis.     

Facile synthesis of high surface area molybdenum carbide nanoparticles

Molybdenum carbide has immense potential as an active catalyst for reaction systems such as synthesis of important chemicals like ammonia. However, the carbide is not used as a commercial catalyst or support as the current synthesis processes produce low surface area material or have contaminants such as excess carbon and surface and chemisorbed oxygen. Moreover, attempts to refine the synthesis pathways are usually not supported by any thermochemical modeling. In this study, a facile and reproducible method to synthesize high surface area molybdenum carbide was developed with the help of thermochemical modeling to better understand molybdenum-carbon phase behavior. We have synthesized 2-5 nm particles of Mo_xC with surface areas of up to 360 m²/g as characterized using a variety of techniques including X-ray diffraction and electron microscopy.