title: Involvement of cyan and ester groups in surface interactions of aerosil-cyanophenyl alkyl benzoate systems with high silica density: Infrared investigations.
abstract: Composites prepared from aerosil A380 and liquid crystals (LCs) of 4-n-alkyl-4'-cyanophenyl benzoate type, with four to six carbon atoms in the alkyl chain were investigated by infrared spectroscopy. Their high silica content (of 2-7 g aerosil/1 g of LC) was given by thermogravimetric investigations and allows the observation of a rather thin LC layer on the silica particles. Several surface species onto the external surface of the grains were demonstrated. Arguments are given that monomer and dimer species are present in the bulk cyanophenyl benzoate materials while bulk-like species along with hydrogen-bonded ones coexist in the so-called surface layer of the composites. The main interaction of LC molecules with the aerosil surface is by hydrogen bonding taking place with the involvement of the cyan group. There is a contribution of ester carbonyl group to these surface interactions but this cannot be well quantified.
authors.affiliation: National Institute of Materials Physics, R-077125 Magurele, Romania. lfrunza@infim.ro
authors.forename: Ligia
authors.initials: L
authors.lastname: Frunza
authors.forename: Stefan
authors.initials: S
authors.lastname: Frunza
authors.forename: Irina
authors.initials: I
authors.lastname: Zgura
authors.forename: Traian
authors.initials: T
authors.lastname: Beica
authors.forename: Nicoleta
authors.initials: N
authors.lastname: Gheorghe
authors.forename: Paul
authors.initials: P
authors.lastname: Ganea
authors.forename: Daniel
authors.initials: D
authors.lastname: Stoenescu
authors.forename: Adrian
authors.initials: A
authors.lastname: Dinescu
authors.forename: Andreas
authors.initials: A
authors.lastname: Schönhals
mesh_terms: D001565:Benzoates / Q000737:chemistry*; D002152:Calorimetry, Differential Scanning; D004952:Esters / Q000737:chemistry*; D044367:Phase Transition; D012822:Silicon Dioxide / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D013499:Surface Properties; D013696:Temperature; D013818:Thermogravimetry
chemical_list: D001565:Benzoates; D004952:Esters; D012822:Silicon Dioxide