Preparation of Novel Hydrolyzing Urethane Modified Thiol-ene Networks

Novel tetra-functional hydrolyzing monomers were prepared from the reaction of TEOS and select alkene-containing alcohols, ethylene glycol vinyl ether or 2-allyloxy ethanol, and combined with trimethylolpropane tris(3-mercaptopropionate) (tri-thiol) in a thiol-ene “click” polymerization reaction to produce clear, colorless thiol-ene networks using both radiation and thermal-cure techniques. These networks were characterized for various mechanical characteristics, and found to posses Tg’s (DSC), hardness, tack, and thermal stability (TGA) consistent with their molecular structures. A new ene-modified urethane oligomer was prepared based on the aliphatic polyisocyanate Desmodur® N 3600 and added to the thiol-ene hydrolyzable network series in increasing amounts, creating a phase-segregated material having two Tg’s. An increase in water absorption in the ene-modified urethane formulations leading to a simultaneous increase in the rate of hydrolysis was supported by TGA data, film hardness measurements, and an NMR study of closely related networks. This phenomenon was attributed to the additional hydrogen bonding elements and polar functionality brought to the film with the addition of the urethane segment. SEM was utilized for visual analysis of topographical changes in the film’s surface upon hydrolysis and provides support for surface-driven erosion. Coatings prepared in this study are intended for use as hydrolyzing networks for marine coatings to protect against ship foulin

Selective Complexation and Reactivity of Metallic Nitride and Oxometallic Fullerenes with Lewis Acids and Use as an Effective Purification Method

Metallic nitride fullerenes (MNFs) and oxometallic fullerenes (OMFs) react quickly with an array of Lewis acids. Empty-cage fullerenes are largely unreactive under conditions used in this study. The reactivity order is Sc4O2@Ih-C80 \u3e Sc3N@C78 \u3e Sc3N@C68 \u3e Sc3N@D5h-C80 \u3e Sc3N@Ih-C80. Manipulations of Lewis acids, molar ratios, and kinetic differences within the family of OMF and MNF metallofullerenes are demonstrated in a selective precipitation scheme, which can be used either alone for purifying Sc3N@Ih-C80 or combined with a final high-performance liquid chromatography pass for Sc4O2@Ih-C80, Sc3N@D5h-C80, Sc3N@C68, or Sc3N@C78. The purification process is scalable. Analysis of the experimental rate constants versus electrochemical band gap explains the order of reactivity among the OMFs and MNFs

Preferential Encapsulation and Stability of La\u3csub\u3e3\u3c/sub\u3eN Cluster in 80 Atom Cages: Experimental Synthesis and Computational Investigation of La\u3csub\u3e3\u3c/sub\u3eN@C\u3csub\u3e79

We report the synthesis and electronic stabilization of La3N@C79N. Unsuccessful efforts to encapsulate bulky La3N clusters in small C80 cages have been attributed to large ionic radii. The preferred species for La3N clusters in all-carbon cages is La3N@C96. A surprising finding is the synthesis of La3N@C79N, a new metallofullerene present in higher abundance than La3N@C96. This reduction in cage size from 96 to 80 atoms reflects the significance and role of electronic effects. To understand the geometric and electronic properties of this first metallic nitride azafullerene (M3N@C79N, M = La), density functional theory (DFT) investigations were performed on a number of isomers. Results indicate a preferred N-substitution at the 665 junction site on the cage in lieu of a 666 substitution. The relative stabilities of different isomers can be well reproduced by using the minimum distance between the metal atom and the nitrogen atom of the cage (RN′Mmin). Long RN′Mmin values indicate distant contacts between six atoms that bear significantly large positive charges: the three metal atoms and the three carbon atoms bonded with the nitrogen atom in the cage, which are favored. These results suggest a dominant electronic effect on the stabilities of metalloazafullerenes. Interestingly, spin densities of the 665 substitution isomers of La3N@C79N are located predominantly in the metal cluster, while spin densities of the 666 substitution isomers are primarily on the cage

Dispersion of Gold Nanoparticles in UV-Cured, Thiol-Ene Films by Precomplexation of Gold-Thiol

Alkyl thiols and alkenes (enes) polymerize via an extremely rapid step-growth, free-radical chain process, uninhibited by air, to give high-density networks with excellent mechanical and physical properties. These thiol−ene coatings are potentially useful for a wide variety of coatings, adhesives, and optical applications. In this work, a series of nanogold-containing UV-cured, thiol−ene coatings were prepared from trimethylolpropane tris(3-mercaptopropionate) (trithiol) and pentaerythritol allyl ether (triene) monomers using a unique procedure which facilitates precomplexation of the gold−thiol prior to photocuring. Irgacure 651 (1 wt %) was used as a photoinitiator, and nanogold was incorporated at 0−1 wt %, average ∼10 nm size particles by TEM. Physical and mechanical properties were characterized using bulk tack analysis and other standard techniques: DSC, TGA, pencil hardness, and gel fractions. In general, films were found to be low absorbing in the visible range and highly uniform and to contain well-dispersed nanogold particles. Although the rate of polymerization was modestly retarded by the presence of gold nanoparticles, functional group conversions (C═C and S−H) and gel fractions were high. Increasing nanogold content resulted in an increase in Tg measured by DSC (−15 to −8 °C for 0−1 wt % nanogold, respectively) due to the increasing number of physical gold−thiol cross-links created. TGA analysis revealed a small negative impact of increasing nanogold composition on relative thermal stability. The 1 wt % nanogold-containing samples possessed appreciable electrostatic discharge (ESD) character, with ESD times of 1−10 s measured using a commercial charge plate analyzer

Sc\u3csub\u3e2\u3c/sub\u3e(μ\u3csub\u3e2\u3c/sub\u3e-O) Trapped in a Fullerene Cage: The Isolation and Structural Characterization of Sc\u3csub\u3e2\u3c/sub\u3e(μ\u3csub\u3e2\u3c/sub\u3e-O)@\u3cem\u3eC\u3c/em\u3e\u3csub\u3e\u3cem\u3es\u3c/em\u3e\u3c/sub\u3e(6)-C\u3csub\u3e82\u3c/sub\u3e and the Relevance of the Thermal and Entropic Effects in Fullerene Isomer Selection

The new endohedral fullerene, Sc2(μ2-O)@Cs(6)-C82, has been isolated from the carbon soot obtained by electric arc generation of fullerenes utilizing graphite rods doped with 90% Sc2O3 and 10% Cu (w/w). Sc2(μ2-O)@Cs(6)-C82 has been characterized by single crystal X-ray diffraction, mass spectrometry, and UV/vis spectroscopy. Computational studies have shown that, among the nine isomers that follow the isolated pentagon rule (IPR) for C82, cage 6 with Cs symmetry is the most favorable to encapsulate the cluster at T \u3e 1200 K. Sc2(μ2-O)@Cs(6)-C82 is the first example in which the relevance of the thermal and entropic contributions to the stability of the fullerene isomer has been clearly confirmed through the characterization of the X-ray crystal structure

Poly(perfluoroalkylation) of Metallic Nitride Fullerenes Reveals Addition-Pattern Guidelines: Synthesis and Characterization of a Family of Sc\u3csub\u3e3\u3c/sub\u3eN@C\u3csub\u3e80\u3c/sub\u3e(CF\u3csub\u3e3\u3c/sub\u3e)\u3csub\u3e\u3cem\u3en\u3c/em\u3e\u3c/sub\u3e (\u3cem\u3en\u3c/em\u3e=2â16) and Their Radical Anions

A family of highly stable (poly)perfluoroalky-lated metallic nitride cluster fullerenes was prepared in high-temperature reactions and characterized by spectroscopic (MS, 19F NMR, UV−vis/NIR, ESR), structural and electrochemical methods. For two new compounds, Sc3N@C80(CF3)10 and Sc3N@C80(CF3)12, single crystal X-ray structures are determined. Addition pattern guidelines for endohedral fullerene derivatives with bulky functional groups are formulated as a result of experimental (19F NMR spectroscopy and single crystal X-ray diffraction) studies and exhaustive quantum chemical calculations of the structures of Sc3N@C80(CF3)n (n = 2-16). Electrochemical studies revealed that Sc3N@C80(CF3)n derivatives are easier to reduce than Sc3N@C80, the shift of E1/2 potentials ranging from +0.11 V (n = 2) to +0.42 V (n = 10). Stable radical anions of Sc3N@C80(CF3)n were generated in solution and characterized by ESR spectroscopy, revealing their 45Sc hyperfine structure. Facile further functionalizations via cycloadditions or radical additions were achieved for trifluoromethylated Sc3N@C80 making them attractive versatile platforms for the design of molecular and supramolecular materials of fundamental and practical importance