02386nas a2200205   4500008004100000022001400041245011200055210006900167260007100236300001400307490000800321520157900329100002101908700001801929700003201947700002401979700001902003700002702022856013102049       2008                        eng d  a1520-610600aGelation of covalently edge-modified laponites in aqueous media. 1. rheology and nuclear magnetic resonance0 aGelation of covalently edgemodified laponites in aqueous media 1  a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcAPR  a4536-45440 v1123 a<p>We describe the covalent modification of the edges of laponite with organic groups and the influence of this modification on gelation behavior. We compare three materials: an unmodified laponite, a laponite edge modified with a trimethyl moiety (MLap), and an octyldimethyl moiety (OLap). Gelation is investigated using rheology and NMR T-1 relaxation measurements and nuclear Overhauser enhancement spectroscopy (NOESY). MLap and OLap show qualitatively different gelation. Gelation of MLap is very similar to laponite: MLap gels over the same time scale as laponite and has about the same solid modulus, and the MLap gel is almost as transparent as laponite. In contrast, OLap gels rapidly relative to laponite and forms a weak, turbid gel. We believe that gelation in laponite and MLap results from the formation of a network of well-dispersed platelets (or a few platelets), while in OLap, gelation results from a network of stacks of several platelets. NMR relaxation measurements indicate that gelation does not affect the average relaxation of water protons. However, T, increases marginally for the protons in the organic moieties in MLap and decreases for protons in the organic moieties in OLap. Relaxation measurements, analyses of line width, and NOESY taken together suggest that, in OLap, gelation is a consequence of association of the organic moieties on the laponite edges, and that this association strengthens with time. Thus, the time-dependent changes in NMR suggest a structural origin for the time-dependent changes in the rheological behavior.</p>1 aPatil, Suhas, P.1 aMathew, Renny1 aAjithkumar, Thalasseril, G.1 aRajamohanan, P., R.1 aMahesh, T., S.1 aKumaraswamy, Guruswamy  uhttps://library.ncl.res.in/content/gelation-covalently-edge-modified-laponites-aqueous-media-1-rheology-and-nuclear-magnetic-001968nas a2200289   4500008004100000022001400041245008100055210006900136260006700205300001200272490000700284520110000291653000601391653000601397653002501403653000901428653000801437653000901445653000901454653000801463653001701471653001401488100002301502700001701525700002401542856011201566       2013                        eng d  a0749-158100aGIAO/DFT studies on 1,2,4-triazole-5-thiones and their propargyl derivatives0 aGIAODFT studies on 124triazole5thiones and their propargyl deriv  a111 RIVER ST, HOBOKEN 07030-5774, NJ USAbWILEY-BLACKWELLcDEC  a767-7740 v513 a<p>Density functional theory (DFT)/Becke-Lee-Yang-Parr (B3LYP) and gauge-including atomic orbital (GIAO) calculations were performed on a number of 1,2,4-triazole derivatives, and the optimized structural parameters were employed to ascertain the nature of their predominant tautomers. C-13 and N-15 NMR chemical shifts of 3-substituted 1,2,4-triazole-5-thiones and their propargylated derivatives were calculated via GIAO/DFT approach at the B3LYP level of theory with geometry optimization using a 6-311++G** basis set. A good agreement between theoretical and experimental C-13 and N-15 NMR chemical shifts could be found for the systems investigated. The data generated were useful in predicting N-15 chemical shifts of all the nitrogen atoms of the triazole ring, some of which could not be obtained in solution state N-15 HMBC/HSQC NMR measurements. The energy profile computed for the dipropargylated derivatives was found to follow the product distribution profile of regioisomers formed during propargylation of 1,2,4-triazole thiones. Copyright (c) 2013 John Wiley &amp; Sons, Ltd.</p>10a110a210a4-triazole-5-thiones10aC-1310aDFT10aGIAO10aN-1510aNMR10aRegioisomers10atautomers1 aPhalgune, Usha, D.1 aVanka, Kumar1 aRajamohanan, P., R.  uhttps://library.ncl.res.in/content/giaodft-studies-124-triazole-5-thiones-and-their-propargyl-derivatives-0