Serge Geribaldi

Highly fluorinated thermotropic liquid crystals: an update

Abstract Fluorine is used in liquid crystal materials in order to give them particular properties as compared to their hydrocarbon homologues. This leads to use of the new compounds as materials mainly in display devices such as Twisted Nematic Liquid Crystals Display (TNLCD) or for the development of Surface Stabilized Ferroelectric smectic C* display (SSFLCDs). In this paper, we describe recent studies and research effort concerning the liquid crystalline behavior of compounds incorporating a highly fluorinated part with more than one fluoromethylene units. We examine some of their mesophase properties and the impact of molecular shape on the resulting liquid crystal behavior.

Polymerizable semi-fluorinated gemini surfactants designed for antimicrobial materials.

Introduction of biocide monomers during the process of polymerization is one of promising approaches in the development of new permanent non leaching biocide materials. In this perspective, new polymerizable semi-fluorinated gemini surfactants, with quaternary ammonium groups as polar heads and an acrylic function as the polymerizable moiety, were synthesized and tested to evaluate their surface active properties alongside with their antibacterial and antifungal properties. Four microbial strains, known for their implication in nosocomial infections, were used to perform the study: Pseudomonas aeruginosa, Staphylococcus aureus, Candida albicans and Aspergillus niger. The biocide efficacy measured by bacterial and fungal growth inhibition expressed as MIC (minimal inhibitory concentration) and MLC (minimal lethal concentration) values was discussed as a function of molecular parameters. As compared to homologue compounds without acrylic part, this study shows that even the introduction of a polymerizable moiety allows to keep remarkable both surfactant and bacteriostatic activities, and allows us to envisage the use of these surfactant monomers to build up advanced biocide materials. Moreover, semi-fluorinated gemini surfactant monomers with an amide connector came out as broad spectrum biocides (against Gram positive and negative bacteria and fungi).

Antimicrobial properties of highly fluorinated bis-ammonium salts

Four series of new highly fluorinated bisammoniums (Quaterfluo Tx, Quaterfluo Bx, Quaterfluo Cx, Quaterfluo Dx) were tested to evaluate their anti-bacterial and anti-fungal properties. Four microbial strains were used to perform the study: Pseudomonas aeruginosa, Staphylococcus aureus, Candida albicans and Aspergillus niger. The antimicrobial efficacy was measured by bacterial and fungal growth inhibition expressed as minimal inhibitory concentration (MIC) values. The Quaterfluo Tx series had very good antimicrobial activity, particularly against Gram-negative bacteria. A speed of kill test carried out with Quaterfluo T3 showed bactericidal activity. The introduction of perfluorinated chains into the quaternary ammonium surfactant structure leads to particularly active antimicrobial agents which not only have bacteriostatic properties but which could be also powerful bactericides.

Fabrication of Superhydrophobic PDMS Surfaces by Combining Acidic Treatment and Perfluorinated Monolayers

In this paper, polydimethylsiloxane (PDMS) with a superhydrophobic surface was generated by the combination of an acid corrosion followed by the covalent grafting of a highly fluorinated monolayer. The acid corrosion was performed with H2SO4 or HF, and the more effective was concentrated H2SO4. The resulting surface had a contact angle with water of 135 degrees. All the acid-treated samples were then functionalized by the covalent grafting of triethoxyaminopropylsilane followed by the reaction with semifluorinated acid chlorides, via the formation of an amide bond, or directly by a commercially available highly fluorinated silane, 1H,1H,2H,2H-perfluorodecyltriethoxysilane, to afford superhydrophobic surfaces (contact angle with water exceeding 160 degrees). The introduction of an amide function in the fluorinated monolayer afforded the best water repellency properties probably due to the organization induced by H-bonding between the surface grafted molecules.

Synthesis and antimicrobial properties of polymerizable quaternary ammoniums

Introduction of biocide monomers during the process of polymerization is a promising approach in the development of new permanent non leaching biocide materials. Two series of surfactants monomers, with a quaternary ammonium group as polar head and an acrylic function as the polymerizable moiety, were synthesized and tested to evaluate their surface active properties alongside with their antibacterial and antifungal properties. Four microbial strains were used to perform the study: Pseudomonas aeruginosa, Staphylococcus aureus, Candida albicans and Aspergillus niger. The biocidal efficacy measured by bacterial and fungal growth inhibition expressed as MIC (Minimal Inhibitory Concentration) and MLC (Minimal Lethal Concentration) values was discussed as a function of molecular parameters. All the synthesized surfactant monomers presented bactericidal and fungicidal activities. Increasing the spacer between the acrylic part and the ammonium group has a favourable effect on the MIC and MLC results.

Mechanically polished copper surfaces modified with n-dodecanethiol and 3-perfluorooctyl-propanethiol

Abstract Mechanically polished copper substrates modified with ethanolic solutions (10 −3 and 10 −2 M) of n -dodecanethiol and 3-perfluorooctyl-propanethiol have been evaluated by X-ray photoelectron spectroscopy, contact angles and cyclic voltammetry measurements. In spite of the fact that ethanol is not necessarily the best solvent, our results show that it is possible to graft highly perfluorinated alkanethiols as well as alkanethiols on copper substrates.

Fourier transform mass spectrometric studies of isovalent rare earth ions Sc+, Y+ and Lu+ with methanol. Formation of dimethoxide—metal species M(OCH3)+2

Abstract The primary and subsequent gas-phase reactions between methanol and the isovalent rare earth metal ions Sc + , Y + and Lu + have been investigated using a Fourier transform ion cyclotron resonance mass spectrometer. The three metal ions react exothermically with methanol. Among the primary reaction products obtained, only two are common to the three metals, the hydroxide—metal ions MOH + , and the methoxide—metal ions MOCH + 3 . For Sc + and Y + , as primary products the metal oxide ions MO + , and the metal—formaldehyde complexes M(OCH 2 ) + , are also observed, as well as the formation of the metal—dihydride ion MH + 2 (only for Y + ). All the primary ions undergo subsequent reactions with methanol, and the final product is always the M(OCH 3 ) 2 (CH 3 OH) + n species ( n = 0–3). The results are analysed to yield the lower and/or upper limits for bond energies: D °(M + OH) and D °(HOM + OH) > 92 kcal mol −1 , D °(HOM + OCH 3 ) and D °(M + OCH 3 ) > 105 kcal mol −1 for M  and Lu, D °(HOSc + OCH 3 ) and D °(Sc + OCH 3 ) > 119 kcal mol −1 , D °(ScOH) −1 , D °(YOH) −1 , and D °(LuOH) −1 .

X-Ray photoelectron spectroscopy study of polycrystalline zinc modified by n-dodecanethiol and 3-perfluorooctyl-propanethiol

Two types of zinc substrates, mechanically polished and electrochemically reduced, modified with n-dodecanethiol and 3-perfluorooctyl-propanethiol have been evaluated by X-ray photoelectron spectroscopy. For both types of organothiols, it is found that the electrochemically reduced substrates lead to modified surfaces of much better quality than those obtained on the mechanically polished substrates.

Gas-phase reactivity of rare earth cations with phenol: competitive activation of C–O, O–H, and C–H bonds

The gas-phase reactions of Sc+, Y+, and Ln+ (Ln=La-Lu, except Pm) ions with phenol were studied by Fourier transform ion cyclotron resonance mass spectrometry. All the ions except Yb+ were observed to react with the organic substrate, activating O-H, C-O, and/or C-H bonds, with formation of MO+, MOH+, and/or MOC6H4+ ions as primary products. The product distributions and the reaction efficiencies obtained showed the existence of important differences in the relative reactivity of the rare earth metal cations, which are discussed in terms of factors like the electron configurations of the metal ions, their oxophilicity, and the second ionization energies of the metals. The primary product ions participated in subsequent reactions, yielding species such as M(OH)(OC6H5)+, which lead mainly to M(OC6H5)2(HOC6H5)n+ ions, where n=0–2. Formation of M(OC6H5)(HOC6H5)n+ species was also observed in the case of the metals that have high stabilities of the formal oxidation state 2+, Sm and Eu.

Gas-phase reactions of Sc+, Y+, and Lu+ with alcohols. Effects of the class and chain length of alcohols on the nature of primary products

The primary gas-phase reactions between methanol, ethanol, propan-1-ol, propan-2-ol, and 2-methyipropan-2-ol and the isovalent rare earth metal ions Sc+, Y+, and Lu+ generated by laser desorption-ionization of metal targets have been investigated by using a Fourier transform ion cyclotron resonance mass spectrometer. The three metal ions react exothermically with all the alcohols. The overall reactivity is controlled by the high oxophilicity of these metals, and the primary metallated ions obtained are principally oxygenated species. However, the number and the nature of these primary products depends on the electronic configuration of the metal ions as well as on the class and the principal chain length of alcohols. The order of reactivity is Y+ > Sc+ > Lu+. The Y+ and Sc+ ions principally react via C—O and O—H insertions, whereas Lu+ reacts by direct abstraction or via various five-center electrocyclic mechanisms as a function of the class and the alcohol chain length.