Monomers

Abstract— The radical copolymerization of (p-2-ethoxycarbonyl)cyclopropyl styrene with glycidyl methacrylate has been investigated. The new cyclopropane- and epoxy-containing photosensitive copolymers have been prepared. The constant values of relative activity of the monomers have been determined and the parameters Q-e on Alfrey and Price have been calculated. The copolymerization constants of this compound (r1) with glycidyl methacrylate (r2) calculated on Feynman-Ross method are: r1 = 1.15, r2 = 0.42, respectively; values of parameters Q and e: Q1 = 1.85, e1 = -0.75, respectively. The composition and structure have been established and the photochemical investigations of the synthesized copolymer have been carried out. It has been established that structuring proceeds due to opening of cyclopropane ring, epoxide and carbonyl groups.

Recent findings in the synthesis of perfluoro-hypofluorites, their reactivity and their use in the preparation of important perfluoro monomers are herein summarized and analyzed. The experimental conditions to induce free radical or electrophilic reactivity as well as their use as initiation system in the oxidation and oxypolimerization of fluorinated olefins are also presented.

Particular emphasis is dedicated to safety issues since organic hypofluorites have the tendency to self-decompose forming gaseous compounds.The hypofluorites considered in this review are: CF3OF, CF2(OF)2, CF3CF2OCF2OF, CF3OCF2CF2OCF2OF, CF3O(CF2O)nCF2OF, CF3OCF2CF2OF, (CF3)2CFOF (CF3)3COF, FS(O)2CF2CF2OF, CF3OCF2CF2CF2OF, cyclo-(CF2OCF2OCF)-CF2OF, (CF3)2N-CF2OF

In the title molecule, C18H12N2O4S, the carbazole skeleton is
nearly planar [maximum deviation = 0.037 (1) A ° ] and is
oriented at a dihedral angle of 73.73 (5) with respect to the
benzene ring. An intramolecular C—H  O hydrogen bond
links a nitro O atom to the carbazole skeleton. In the crystal,
intermolecular C—H  O hydrogen bonds link the molecules
into a three-dimensional network. – contacts between
inversion-related benzene rings [centroid–centroid distance =
3.7828 (8) A ° ] and two w

Several 3-alkoxy-5, 7-diiodo-6-fluorones (λmax ≈ 470 nm) have been synthesized and evaluated as initiators for photopolymerization triggered with the 515.5 nm line of an Ar+ laser. 2-Acyl- and 2-alkyl-4,5,7-triiodo-3-hydroxy-6-fluorones were also tested at 515.5 nm. 9-Cyano-2-Acyl- and 9-cyano-2-alkyl-4,5,7-triiodo-3-hydroxy-6-fluorones were studied and could be excited with the 632 nm line of a He–Ne laser. Dyes with long linear carbon chain alkoxy groups at C-6 showed larger molar extinction coefficients and formed polymers with better mechanical properties than did compounds with shorter carbon chains, or did the corresponding C-6 phenols. The optimum side chain length of the C-6 ether alkyl group is between 4–7 carbon atoms. With longer carbon chain alkoxy groups at C-8, e.g., octyl, the mechanical properties of the formed polymers are inferior to systems formed with the butyl isomer as photoinitiator. In the case of alkoxy groups with branched alkyl groups (e.g., 2-ethylbutyl), the relationship between dye structure and the properties of the polymers formed is less straightforward. Though the dyes react from their triplet state, the fluorescence quantum yields of the dyes and the performance of the dyes as photoinitiators appear directly related. © 1995 John Wiley & Sons, Inc.

Composite dental restorations represent a unique class of biomaterials with severe restrictions on biocompatibility, curing behavior, esthetics, and ultimate material properties. These materials are presently limited by shrinkage and polymerization-induced shrinkage stress, limited toughness, the presence of unreacted monomer that remains following the polymerization, and several other factors. Fortunately, these materials have been the focus of a great deal of research in recent years with the goal of improving restoration performance by changing the initiation system, monomers, and fillers and their coupling agents, and by developing novel polymerization strategies. Here, we review the general characteristics of the polymerization reaction and recent approaches that have been taken to improve composite restorative performance.

Multi-walled carbon nanotube (MWCNT)/C/polystyrene (PS) composite materials were prepared by in situ polymerization of monomer in preformed MWCNT/C foams. MWCNT/C foams were preformed using polyurethane foam as template. The preformed MWCNT/C foams had a more continuous conductive structure than the carbon nanotube networks formed by free assembly in composites. The structure of the MWCNT/C foam network was characterized with scanning electron microscopy. The MWCNT/C/PS composites have an electric conductivity higher than 0.01S/cm for a filler loading of 1wt.%. Enhancement of thermal conductivity and mechanical properties by the preformed MWCNT/C foam were also observed.

New methacrylic monomers containing pendant azobenzene structures have been prepared by reacting azobenzene assemblies possessing phenolic functions with methacryloyl chloride. The most favorable synthetic routes are described together with the yields obtained. The new monomers have been purified and completely characterized by elemental analysis and melting points, as well as by recording their UV, FT-IR and NMR spectra.

In the past, several unsuccessful attempts have been made to dissociate homodimeric enolases into their active monomeric forms. The main objective of these studies had been to understand whether intersubunit interactions are essential for the catalytic and structural stability of enolases. Further motivation to investigate the properties of monomeric enolase has arisen from several recent reports on the involvement of enolase in diverse nonglycolytic (moonlighting) functions, where it may occur in monomeric form. Here, we report successful dissociation of dimeric enolases from Plasmodium falciparum, yeast and rabbit muscle into active and isolatable monomers. Dimeric enolases could be dissociated into monomers by high concentrations (∼ 250 mm) of imidazole and/or hydrogen ions. Two forms were separated using Superdex-75 gel filtration chromatography. A detailed comparison of the kinetic and structural properties of monomeric and dimeric forms of recombinant P. falciparum enolase showed differences in specific activity, salt-induced inhibition and inactivation, thermal stability, etc. Furthermore, we found that enolases from the three species differ in their dimer dissociation profiles. Specifically, on challenge with imidazole, Mg(II) protected the enolases of yeast and rabbit muscle but not of P. falciparum from dissociation. The observed differential stability of the P. falciparum enolase dimer interface with respect to mammalian enolases could be exploited to selectively dissociate the dimeric parasite enzyme into its catalytically inefficient, thermally unstable monomeric form. Thus enolase could be a novel therapeutic target for malaria.

Two major limiting factors in the use of cyanate ester resins for high-temperature aerospace applications are durability in hot/wet environments and the trade-off between obtainable glass transition temperatures and ease of processing. In order to understand how the molecular-level structure of cyanate ester resins relates to both of these issues, studies of cyanate ester monomers with novel chemical structures as well as studies of monomer blends are underway at the Air Force Research Laboratory. In particular, new tricyanate ester monomers containing mixtures of stereochemical isomers have exhibited significantly improved processability, while studies of ternary monomer blends provide a unique means of testing various mechanisms of moisture uptake.