William L. Jarrett

Nafion®/ORMOSIL nanocomposites via polymer-in situ sol–gel reactions. 1. Probe of ORMOSIL phase nanostructures by 29Si solid-state NMR spectroscopy

Abstract A series of Nafion®/ORMOSIL hybrids, generated by in situ sol–gel co-polymerizations of tetraethylorthosilicate (TEOS) and semi-organic R′nSi(OR)4−n co-monomers (SOC), were developed to generate a spectrum of nanoscale chemical environments within the Nafion® morphological template. The molecular structures of the ORMOSIL phases were analyzed by means of 29Si solid-state NMR (SSNMR) spectroscopy. A high average degree of Si atom coordination about SiO4 molecular sub-units can be achieved, but a significant number of unreacted SiOH groups on reacted Q=Si(O1/2)4 units is always present. The shifting, with relative ORMOSIL composition, of D=RR′Si(O1/2)2 or T=R″Si(O1/2)3 (R, R′ and R″ are organic moeities) peak envelopes for difunctional or trifunctional SOCs is suggested to reflect random co-condensation rather than distinct Q and D (or T) block formation. The numbers of membrane-incorporated Q and D (or T) units per fixed sulfonate group were calculated from the 29Si SSNMR spectra for those particular hybrids that had a reasonably low noise/signal aspect. Spectra for hybrids based on in situ sol–gel reactions for TEOS (no SOC present) suggest that inserted hydroquinone molecules interfere with condensation reactions between (RO)4−xSi(OH)x molecules and silanol oligomers to yield silicate structures with lower average coordination. While earlier small angle X-ray scattering studies indicated that ORMOSIL structures can be grown within the polar regions of Nafion®, the results reported here address the specific compositions of these nanoscale structures.

Chemical modification of a Nafion® sulfonyl fluoride precursor via in situ sol-gel reactions

Abstract The melt-processible sulfonyl fluoride precursor of a Nafion® ionomer was utilized as a sol gel reaction medium for 3-aminopropyltriethoxysilane (APrTEOS). The diffusion-mediated reaction of APrTEOS with SO2F groups can be controlled with high degree of reaction. Fourier transform infra-red/attenuated total reflection studies show that sulfonamide linkages are formed and condensation reactions of SiOR groups provide covalent crosslinking of chains. Formic acid treatment plus high temperature plus long time resulted in a high degree of polymer crosslinking as seen in 29Si solid state nuclear magnetic resonance spectra. Mechanical modulus and strength increase, and elongation-to-break decreases with increasing filler. Hybrids with

Novel Nafion®/ORMOSIL hybrids via in situ sol-gel reactions: 2. Probe of ORMOSIL phase nanostructure by 29Si solid state NMR spectroscopy

Perfluorosulfonic Acid (PFSA)]/[Organically-Modified Silicon Oxide (ORMOSIL)] hybrids were formulated via sol-gel reactions of mixtures of tetraethoxysilane (TEOS) and diethoxydimethylsilane (DEDMS) in the nanophase-separated morphology of a PFSA membrane (Nafion®). The molecular structures of the ORMOSIL phases were investigated by 29Si solid state NMR spectroscopy and the spectra compared with those of corresponding bulk ORMOSILs. PFSA-in situ ORMOSIL composition can be tailored by manipulating TEOS/DEDMS source solution composition and quantified by 29Si solid state NMR spectroscopy. Copolymerization of TEOS and DEDMS monomers, rather than block formation, occurs within the PFSA as well as in the bulk. As DEDMS feed concentration increases, ORMOSIL nanostructures are more hydrophobic and more flexible. Dimethylsiloxane rings are dominant in PFSAs in which hydrolysis + condensation of pure DEDMS occurs.

Structural changes in trisilanol POSS during nanocomposite melt processing

The nanofiller, 1,3,5,7,9,11,14-hepta-2,2,4-trimethylpentyl-tricyclo[7.3.3.1(5,11)] heptasiloxane-endo-3,7,14-triol, T-POSS, was recently demonstrated to increase modulus retention in poly(ethylene terephthalate) fibers. In this paper, changes in the structure of T-POSS were studied as a function of time, temperature, and air vs. nitrogen atmosphere. These structural changes were studied using TGA, FTIR, MALDI-TOF, and NMR spectroscopy. T-POSS was observed to undergo an initial weight loss of approximately 8 wt% at temperatures below 250°C under either atmosphere, which is attributed to loss of volatile contaminates in the starting silsesquioxane. Heating T-POSS to the PET processing temperature of 280°C under nitrogen atmosphere results in production of a resinous organosilicate material which retains its isooctyl groups, and which contains, at least in part, structures with molecular weights greater than the starting silsesquioxane. Heating this resinous material to temperatures well above 280°C then leads to loss of volatile products with residual char products present in less than 10 wt%. Heating T-POSS to temperatures of 280–1000°C under air causes loss of organic species with 30–40 wt% residual inorganic silicate. While this study demonstrates that when T-POSS is exposed to a temperatures equivalent to those encountered during melt processing with polymers, such as PET, the exposure times during such processing is relatively low, generation of large yields of POSS decomposition products during melt processing is not consistent with the observed degradation kinetics.

Highly potent anti-proliferative effects of a gallium(III) complex with 7-chloroquinoline thiosemicarbazone as a ligand: Synthesis, cytotoxic and antimalarial evaluation

A gallium(III) complex with 7-chloroquinoline thiosemicarbazone was synthesized and characterized. The complex proved to be thirty-one times more potent on colon cancer cell line, HCT-116, with considerably less cytotoxicity on non-cancerous colon fibroblast, CCD-18Co, when compared to etoposide. Its anti-malarial potential on 3D7 isolate of Plasmodium falciparum was better than lumefantrine.

An in vitro study on the effect of synthesized tin(IV) complexes on glioblastoma, colorectal, and skin cancer cell lines

(E)-2-(2-hydroxybenzylideneamino)phenolato-2,2-diphenyl-6-aza-1,3-dioxa-2-stanna-[d,h]dibenzocyclononene, [Sn(Ph2SB)] (compound 1, where Ph2SB=(E)2-(2-hydroxybenzylideneamino)phenolato Schiff base) and two novel compounds, [[SnPh2(F-azoSB)] (compound 2, where F-azoSB=4-((E)-(4-fluorophenyl) diazenyl)-2-((E)-(2-hydroxyphenylimino)methyl)phenolato Schiff base), [[SnPh2(sulf-azoSB)]0.125CHCl3 (compound 3, where sulfamerazineazosalSB=4-((E)(4-hydroxy-3-((E)-(2-hydroxyphenylimino)methyl)phenyl)diazenyl)-N-(4-methylpyrimidin-2-yl) benzenesulfonamide Schiff base), and the control compound, cisplatin (compound 4) were analysed to comparatively determine their effect on cancer cell growth. Anti-cancer properties of compounds 1-4 were examined using glioblastoma (U-1242 MG), colorectal (HT-29 and HCT-116), and skin (A431) human cancer cell lines. With regards to human glioblastoma cells, compounds 1 and 3 demonstrated anti-proliferative capacity in the cell line tested. Specifically, compounds 1 and 3 inhibited cell proliferation by 50% at concentrations between 10 and 50 μM. With respect to colon cancer cell lines, the IC50 values for compounds 1-3 ranged from 3.04 ± 0.98 to 104.51 ± 13.87 μM. In the case of HCT-116, this translates to a 3to 73-fold inhibitory effect of compounds 1-3 over cisplatin. In all cell lines tested, the chemo-effect was more pronounced with compounds 1-3 than with the control (compound 4); demonstrating that these azo-containing Sn(IV) complexes were more potent than compound 4. The overall effect of compounds 1-3 in the induction of appotosis and the inhibition of proliferation have defined an essential role for these compounds in chemotherapy. Correspondence to: Alvin A Holder, Department of Chemistry and Biochemistry, Old Dominion University, 4541 Hampton Boulevard, Norfolk, VA 23529, USA, Tel: 757-683-7102, Fax: 757-683-4628, E-mail: aholder@odu.edu

Conformational and configurational analysis of an N,N carbonyl dipyrrinone-derived oximate and nitrone by NMR and quantum chemical calculations.

The geometries and relative energies of new N,N carbonyl dipyrrinone‐derived oxime molecules (E/Z‐s‐cis 4a and E/Z‐s‐cis 4b) have been investigated. The calculated energies, molecular geometries, and 1H/13C NMR chemical shifts agree with experimental data, and the results are presented herein. The E‐s‐cis conformations of 4a and 4b and the Z‐s‐cis conformation of 5b were found to be the thermodynamically most stable isomers with the oxime hydrogen atom or the methyl functional group adopting an anti‐orientation with respect to the dipyrrinone group. This conformation was unambiguously supported by a number of 2D NMR experiments. Copyright