Francesco A. Bottino

Conformational preference of ortho-substituted diphenyl ethers and diphenyl thioethers

Abstract NMR data are reported for two series of ortho substituted diphenyl ethers (DPO) and diphenyl thioethers (DPS). The results obtained indicate that in these molecules, in addition to steric hindrance effects, conjugative effects may prove important in determining conformational preferences.

Synthesis and characterization of oxygen and sulfur bridged aromatic macrocycles

Abstract The synthesis of nine 16–18–20–22 membered, oxygen and sulfur bridged aromatic macrocycles is reported, and reaction pathways to macrocycles formation are described. Molecular characterization of the nine compounds has been achieved by their mass spectra. Due to the cyclic nature of the compounds analyzed, the mass spectra are of particular interest. The 16–18-membered macrocycles, containing single oxygen and sulfur bridges, display very strong molecular ion intensities, while the 20–22-membered macrocycles, containing double bridges, show lower stability to electron-impact, and the molecular ion intensities are lower. Some of the salient features of the electron fragmentation processes are briefly discussed in the text.

SYNTHESIS AND CHARACTERIZATION OF SCHIFF BASE COMPLEXES WITH ZINC HALIDES

Abstract New complexes with Schiff bases and ZnX2(X[dbnd]Cl · I) have been synthesized. Infrared, CIMS (NH3) and 13C-NMR studies have been used in order to elucidate their structures.

Synthesis, characterization and study of the thermal properties of new polyarylene ethers

Abstract In order to investigate the contrasting propensities for crystallization between aryl sulphone and aryl ketone polymers, new aromatic monomers containing sulphone, ketone and ehter linkages were synthesized and reacted to prepare new polyarylene ethers. The polymers obtained were characterized by solution viscosity, thermal gravimetric analysis and differential scanning calorimetry (d.s.c.). The effect of the presence of ketone and/or sulphone linkages in the polyarylene ethers during synthesis and on the final properties is discussed.

Photoactive Eu(III) and Tb(III) complexes of calix[4]arenes with pyridine-N-oxide pendant groups

Two calix[4]arenes with four 2-pyridyhnethyl-l-oxide pendant groups at the lower rim have been synthesized, and their Tb(III) and Eu(III) complexes are fluorescent upon UV light excitation at 312 nm. The complexes are not stable in aqueous solution, completely losing their luminescent properties.

Kinetic study of the thermal and oxidative degradations of poly(arylenether)s containing quinoline units

Abstract The degradations of five aromatic thermoplastics, in whose repeating units various structures are linked to the same -ArCOQCOAr- moiety (where Ar=1,4-substituted phenylene and Q=3,7-substituted quinoline), were performed in dynamic heating conditions in the temperature range 35–950°C, under nitrogen flow and in static air atmosphere. Experiments under nitrogen suggested that degradations started by random chain scissions, to which branching and crosslinking superimposed at higher temperature, with the formation of residues stable up to 950°C; those in oxidative environment indicated that degradations were due to several processes which were simultaneous at low heating rate and that oxidative stages were involved, as supported by the complete weight loss before the overall temperature scanning. The apparent activation energy values associated with the first degradation stage were obtained by the Kissinger method. Results in inert atmosphere suggested that different linkages were involved in the initial chain scission processes of various polymers and that the comprehensive degradation mechanisms were different from those in air. Anomalous double Kissinger straight lines were found for one of the polymers investigated. The results were discussed and compared with those previously obtained for a similar group of aromatic polymers.

Synthesis and characterization of new poly(arylene ether)s based on dihydroxynaphthalene isomers

Abstract A series of new poly(arylene ether ketone)s and poly(arylene ether sulfone)s, obtained starting from dihydroxynaphthalene isomers, have been prepared by solution condensation polymerization. The polymers, having inherent viscosities from 0.20 to 0.77 dl g −1 , have been obtained in quantitative yields, had excellent thermal stability as shown by 10% weight loss temperatures in nitrogen and air (above 460 and 430°C, respectively) and high glass transition temperatures (in the range 151–278°C). X-ray diffraction patterns confirmed the semicrystalline character of some polymers. The location of the naphthalene-ether bond appears to affect the polymer properties.

The surface photo-oxidation of polystyrene: Part I—The application of ToF-SIMS to monitor changes in polymer chain length

Abstract ToF-SIMS has been employed to monitor the changes in molecular weight which occur on UV irradiation in a polystyrene standard (MW 1700) as a thin film on silver. The ToF-SIMS spectrum of unirradiated polystyrene is also described. Polysiloxane contamination was present in some of the polystyrene samples studied; no effort was made to remove this contamination as it was considered to be part of the system under analysis and proved useful in confirming the role of the phenyl substituent in the photodegradation of polystyrene. Implications of this study, the possible development of the technique described and its application to real polymer surfaces are discussed.

Dynamic stereochemistry of bis(N-isopropylsalicylaldiminato) beryllium(II): enantiomerization process

Bis(N-isopropylsalicylaldiminato)beryllium has been prepared. Its variable temperature 1H NMR spectrum has been investigated in 1,2-dichlorobenzene, and the free energy of activation (22.1 kcal/mole at 139°C) thus determined for enantiomerization (inversion at the beryllium tetrahedral atom) without prior separation of the optical antipodes.

NMR data and conformational preference of orthosubstituted diphenyl sulphones

Abstract NMR data and relative spectral assignments are reported for several di-phenyl sulphones, together with those of some reference methyl phenyl sulphones. Extensive decoupling experiments were of particular help in the assignment of aromatic protons. A concise discussion is reported on the relevant spectral features observed and the conformational properties of the compounds studied.