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71.
Sobhana Mathew Leena Rajith Laina Angamaly Lonappan Theresa Jos Krishnapillai Girish Kumar 《Journal of inclusion phenomena and macrocyclic chemistry》2014,78(1-4):171-177
A polymeric membrane based Pb(II) selective potentiometric sensor was developed by using 1,3,7,9-tetraaza-2,8-dithia-4,10-dimethyl-6,12-diphenylcyclododeca-4,6,10,12-tetraene (TDDDCT) as an electroactive material along with anion excluder sodium tetraphenylborate (NaTPB) and plasticizer dioctylphthalate (DOP). The best performance in terms of slope, concentration range and response time was exhibited by the membrane having TDDDCT:PVC:DOP:NaTPB in the ratio 3:32:62:3 (w/w%). Potentiometric results show that the developed sensor works well in the concentration range 5.0 × 10?7–1.0 × 10?1 M with a near Nernstian slope of 29.5 (±0.5) mV decade?1. The detection limit is down to 2.5 × 10?7 M. The working pH range of this sensor is 2.8–7.0 and it works well in partially nonaqueous medium up to 25 % (v/v) methanol and ethanol. It exhibits a fast response time of 10 s. Selectivity coefficient values of various interfering ions were determined by the fixed interference method (FIM). The sensor reveals good selectivity for Pb(II) ions over other metal ions investigated. The developed sensor is used in the determination of lead in ‘Eveready battery waste’ and as an indicator electrode in the potentiometric titration of Pb(II) against EDTA. 相似文献
72.
Fast‐swelling micrometer sized superabsorbents were synthesized through a rapid solution polymerization of n‐vinyl‐2‐pyrrolidone (NVP) and partially neutralized acrylic acid (PNAAc) under normal atmospheric conditions using N,N'‐methylene bisacrylamide (MB) as crosslinker and sodium bicarbonate as porogen. The effect of various parameters such as crosslinker concentration, degree of neutralization of monomer acid, concentration of initiator have been evaluated. Water retention capacity of superabsorbents under varying loads was also examined. The drying behavior of polymers at 37°C was also studied. The gels showed sharp volume transition in solutions of divalent metal ions. The superabsorbents were also characterized by FTIR and TGA. 相似文献
73.
Leena Nebhani Sebastian Sinnwell Ching Yeh Lin Michelle L. Coote Martina H. Stenzel Christopher Barner‐Kowollik 《Journal of polymer science. Part A, Polymer chemistry》2009,47(22):6053-6071
The synthesis of a novel class of reversible addition‐fragmentation chain transfer (RAFT) agents—based on quantum‐chemical ab initio calculations—having methylsulfonyl and phenylsulfonyl moieties as Z‐group is described. The resulting C‐sulfonyldithioformate transfer agents [benzyl methylsulfonyldithioformate (MSDTF) and benzyl phenylsulfonyldithioformate (PSDTF)] feature extremely strong electron deficient C?S double bonds and should thus be suitable to undergo rapid hetero Diels‐Alder (HDA) reactions with variable dienes under mild (i.e., ambient and catalyst free) reaction conditions. It can be demonstrated via a series of model reactions, whose outcome is monitored via electrospray ionization mass spectrometry (ESI–MS), that C‐sulfonyldithioformate based RAFT agents undergo HDA reactions with a series of diene‐capped macromolecules (10 min < reaction time < 24 h) at ambient temperatures (T ≈ 25 °C) with reaction times ranging from 24 h (for open chain dienes) to a few minutes (for cyclopentadiene) in the absence of any catalysts. Concomitantly, PSDTF is able to efficiently mediate the polymerization of isobornyl acrylate (iBA) with living characteristics (2300 < Mn (g/mol) < 16,000, 1.08 < PDI < 1.31). In a subsequent step, it is demonstrated that conjugates of poly(iBA) and polystyrene can be constructed under mild reaction conditions (reaction time < 10 min, T ≈ 25 °C, Mn ≈ 6000 (g/mol), PDI ≈ 1.3, no catalyst). In addition, we highlight that sulfonyldithioformate type RAFT agents are such effective dienophiles that they can undergo HDA reactions with certain monomers, including styrene. While such a strong HDA activity limits their use in polymerizations, it opens an avenue for catalyst free efficient surface modification reactions under mild conditions with variable dienes. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6053–6071, 2009 相似文献
74.
The aim of the study was to prepare indomethacin nanocrystal-loaded, 3D-printed, fast-dissolving oral polymeric film formulations. Nanocrystals were produced by the wet pearl milling technique, and 3D printing was performed by the semi-solid extrusion method. Hydroxypropyl methyl cellulose (HPMC) was the film-forming polymer, and glycerol the plasticizer. In-depth physicochemical characterization was made, including solid-state determination, particle size and size deviation analysis, film appearance evaluation, determination of weight variation, thickness, folding endurance, drug content uniformity, and disintegration time, and drug release testing. In drug nanocrystal studies, three different stabilizers were tested. Poloxamer F68 produced the smallest and most homogeneous particles, with particle size values of 230 nm and PI values below 0.20, and was selected as a stabilizer for the drug-loaded film studies. In printing studies, the polymer concentration was first optimized with drug-free formulations. The best mechanical film properties were achieved for the films with HPMC concentrations of 2.85% (w/w) and 3.5% (w/w), and these two HPMC levels were selected for further drug-loaded film studies. Besides, in the drug-loaded film printing studies, three different drug levels were tested. With the optimum concentration, films were flexible and homogeneous, disintegrated in 1 to 2.5 min, and released the drug in 2–3 min. Drug nanocrystals remained in the nano size range in the polymer films, particle sizes being in all film formulations from 300 to 500 nm. When the 3D-printed polymer films were compared to traditional film-casted polymer films, the physicochemical behavior and pharmaceutical performance of the films were very similar. As a conclusion, 3D printing of drug nanocrystals in oral polymeric film formulations is a very promising option for the production of immediate-release improved- solubility formulations. 相似文献
75.
Minna Piispanen Leena Hupa 《Applied Surface Science》2011,258(3):1126-1131
This work compares the self-cleaning properties of experimental TiO2 and TiO2-Ag coatings on float glass with a commercial self-cleaning glass. In the experimental surfaces, TiO2 coating was applied to float glass via the sol-gel route, while TiO2-Ag coating was applied by the liquid flame spray method, which deposits TiO2-Ag composite nanoparticles on the surface. The effect of the coatings on the surface wettability and the activation time for achieving hydrophilicity was studied through water contact angle as a function of exposure time to UV light. The surface morphology was investigated by using scanning electron microscopy (SEM) and confocal optical microscopy. The photocatalytic activity of the coatings was examined with methylene blue and stearic acid degradation tests. Finally, the soil attachment to the surfaces was tested with a sebum-based model soil. The sol-gel TiO2 coating became superhydrophilic within a few hours, while the activation time needed for the commercial titania coated glass was several days. The surface with the TiO2-Ag nanoparticles did not show any marked changes in the water contact angle. The commercial titania coated and the sol-gel TiO2 surfaces showed self-cleaning properties and clearly lower attachment of soil than the uncoated and TiO2-Ag coated surfaces. The difference in the interaction of the surfaces with the organic contaminants was assumed to depend mainly on differences in the thickness of the coatings. 相似文献
76.
The polycrystalline samples La0.67Ca0.33Mn(1?x)Fe x O3 (x?=?0.00,?0.01,?0.03, and 0.1) have been grown in single phase by solid state route. The analysis of the reaction has been done by thermogravimetry and differential thermal analysis measurements. DC electrical resistivity measurements have been carried out down to 15?K. The samples with x?=?0.00, 0.01, and 0.03 exhibit metal–insulator (MI) transition at temperatures 221.5?K, 217?K, and 215?K respectively, whereas the sample with x?=?0.1 is insulating in nature for entire temperature range. Interestingly, the electric transport properties of these samples are not consistent with their magnetic phase transitions and the samples show MI transition at a temperature, T MI, which is significantly lower than the paramagnetic to ferromagnetic transition temperature (T c). The resistivity data below T MI has been analyzed using the empirical relation ρ?=?ρ0?+?ρ1 T n and the data above this temperature has been analyzed using two existing models, Mott's variable range hopping model and spin polaronic conduction model. 相似文献
77.
Divya Thomas Laina Lonappan Leena Rajith Soumya T. Cyriac Krishnapillai Girish Kumar 《Journal of fluorescence》2013,23(3):473-478
Fluorescent PET (Photoinduced Electron Transfer) has been of particular growth in recent times. A novel PET based fluorescent sensor using unmodified CdSe quantum dots (QDs) has been developed for the trace determination of Nimesulide (NIM). The sensor is based on the selective fluorescence quenching of quantum dots by NIM in presence of other NSAIDs and is found that intensity of quenching is linearly related to NIM concentration in the range 8.2?×?10?7 – 4.01?×?10?5?M. The mechanism of interaction is discussed. Finally, the potential application of the proposed method for the trace determination of NIM in pharmaceutical formulation is demonstrated. 相似文献
78.
Alaa Alhadad Michael Åkesson Leena Lehti Peter Leander Gunnar Sterner Per Åkeson Johan Wassélius 《Magnetic resonance imaging》2014
Purpose
The purpose of this retrospective study was to systematically search for acute adverse reactions and long-term complications in all patients that had been administered gadofosveset at our hospital.Materials and methods
We identified 67 gadofosveset administrations during 2006–2009 in 62 patients from 8 to 84 years of age. Radiological information system (RIS) and clinical patient records were analyzed for suspected acute adverse reactions and long-term complications including nephrogenic systemic fibrosis (NSF).The gadofosveset doses ranged between 0.024 and 0.060 mmol/kg bodyweight with a mean dose of 0.031-mmol/kg bodyweight. Follow-up time of the patients ranged from less than 1 year up to 4 years with a mean follow-up time of 2.1 years.Results
No acute adverse events or technical failures related to the contrast medium were recorded in the RIS. No dermatological and nephrological diseases related to the gadofosveset administration were found in the clinical patient records. Four patients died during follow-up without any apparent relation to the gadofosveset exposure.Conclusions
Based on our clinical material we conclude that gadofosveset is safe for a mixed patient population with no acute adverse events or any indications of long-term complications during the follow-up time up to four years. 相似文献79.
David J. Lunn Sungbaek Seo Sang‐Ho Lee Raghida Bou Zerdan Kaila M. Mattson Nicolas J. Treat Alaina J. McGrath Will R. Gutekunst Jimmy Lawrence Allison Abdilla Athina Anastasaki Abigail S. Knight Bernhard V. K. J. Schmidt Morgan W. Bates Paul G. Clark Jonathan P. DeRocher Antony K. Van Dyk Craig J. Hawker 《Journal of polymer science. Part A, Polymer chemistry》2019,57(6):716-725
The synthesis and systematic comparison of a comprehensive library of well‐defined polymer architectures based on poly(acrylic acid) is reported. Through the development of new synthetic methodologies, linear, single branched, precision‐branched comb, and star polymers were prepared and their performance as dispersants was evaluated. The ability to accurately control chain lengths and branch points allows the subtle interplay between structure and dispersant performance to be defined and affords critical insights into the design of improved polymeric additives for coating formulations. The general industrial relevance of ionic polymers and branched macromolecular architectures supports these design rules for a wide range of other applications and materials, including as additives for personal care products and in water treatment. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 716–725 相似文献
80.
Merja R. Häkkinen Tuomo A. Keinänen Seppo Auriola Leena Alhonen Jouko Vepsäläinen 《Tetrahedron》2009,65(2):547-5748
Novel di-, tetra- and octadeuterated derivatives of mono-N-alkylated diaminopropanes, spermidines, spermines, symmetrically bis-N-alkylated spermines and unsymmetrically bis-N-alkylated spermines were synthesized. Deuterium labels were introduced into the RHNCH2CH2CN intermediate either by exchanging the protons next to the nitrile group under basic conditions with D2O-EtOD mixture or/and by reducing the nitrile group to a CD2-NH2 fragment with LiAlD4. 相似文献