Bruno Fortunato

Thermal degradation of poly(butylene terephthalate)

Abstract The thermal degradation of poly(butylene terephthalate) between 240° and 280°C has been studied by measurements of intrinsic viscosity, carboxyl end groups and weight loss. A first-order mechanism of fission, followed by elimination of butadiene, is proposed. The values of the kinetic constant and activation energy are in good agreement with those obtained for simple esters and poly(ethylene terephthalate).

Evidence for short-range orientation effects in dipolar aprotic liquids from vibrational spectroscopy. Part 1.—Ethylene and propylene carbonates

The CO stretching frequency of liquid ethylene and propylene carbonates is higher in the infrared than in the Raman spectrum. The difference amounts to 13 cm–1 for ethylene carbonate at 313 K. This effect is explained as the consequence of a coupling between the transition dipoles of neighbouring molecules, which is made possible by some degree of alignment of molecular dipoles due to the high dipole moment of these molecules (about 16 × 10–30 C m). A study of dilution and temperature effects confirms this interpretation.

Infrared and Raman spectra and vibrational assignment of ethylene carbonate

Abstract The infrared spectra of gaseous, liquid and solid ethylene carbonate (the latter in polarized light) and the Raman spectra in the liquid and solid states have been recorded. A complete vibrational assignment is proposed on the basis of gas-phase band contours, depolarization ratios and dichroic ratios; it is found that, although the molecule has C2 symmetry in all three states of aggregation, the liquid and vapour-phase spectra are explainable in terms of C2v pseudo-symmetry. The complex pattern of Fermi resonances in the CO stretching region of the various spectra is interpreted. The correlation field splittings of the most intense totalsymmetric vibrations are quantitatively explained in terms of interactions between transition dipoles.

Infrared and Raman spectra and vibrational assignment of cyclopentadiene

Abstract The infrared spectrum of cyclopentadiene has been recorded from 200 to 4000 cm −1 in the gaseous, liquid and crystalline phases. The Raman spectrum of liquid cyclopentadiene has also been determined with depolarization ratios. All but one of the fundamentals are assigned on the basis of depolarization ratios, gas-phase band contours, and solid-state selection rules. A very large number of overtones and combination tones have been observed and assigned. The interpretation of the combination tones confirms neatly the proposed assignments for the fundamentals, and allows a reasonable value to be suggested for the lacking fundamental.

Vibrational spectra and normal-coordinate treatment of cyclopentadiene and its deuterated derivatives

Abstract The infrared spectra in polarized light and the Raman spectra of crystalline cyclopentadiene and hexadeuterocyclopentadiene and of their solid solutions have been obtained. Pentadeuterocyclopentadiene (1,2,3,4,5) has been prepared for the first time and its i.r. and Raman spectra have been recorded. On the basis of these and previous results, a vibrational assignment is proposed for cyclopentadiene and three of its deuterated derivatives. This assignment is supported by a normal coordinate analysis based on a valence force field.

Models for the formation of poly(butylene terephthalate): Kinetics of the titanium tetrabutylate-catalysed reactions: 2

Abstract In order to investigate the mechanism of catalysis of titanium tetrabutoxide on the polycondensation of poly(butylene terephthalate), this reaction has been studied with the aid of model molecules. The catalytic and retarding effects of benzoic acid have also been taken into account. Appropriate kinetic equations are derived and discussed and the results compared with experimental data obtained at different temperatures and molar ratios of reactants.

Infrared and Raman spectra, conformation and vibrational assignment of acetic and perdeuteroacetic anhydrides

Abstract The infrared spectra of gaseous, liquid and crystalline (CH 3 CO) 2 O and (CD 3 CO) 2 O have been studied (200 to 4000 cm − ) together with the Raman spectra of the liquids. The possibility of a coexistence of two isomeric forms is dicussed, and it is concluded that most probably only one form is present. On the basis of the number of polarized Raman lines and of the intensity ratio between the absorption bands due to carbonyl stretchings, this form should have a non-planar skeleton and belong to the symmetry group C 2 . A complete vibrational assignment, consistent with the Teller-Redlich product rule and with previous assignments for related molecules, is proposed for both (CH 3 CO) 2 O and (CD 3 CO) 2 O.

Solid state polycondensation of poly(butylene terephthalate)

Abstract Solid state polycondensation of poly(butylene terephthalate) has been studied under vacuum at 200°C for various particle sizes. The effect of the process on intrinsic viscosity and number of end groups has been examined. The results suggest that the increasing of the number average molecular weight can be explained by a mechanism involving hydroxyl groups, which approach each other by diffusion until a limiting value of their concentration is attained.

Raman and i.r. spectra of 3-sulfolene

Abstract Raman and i.r. spectra of 3-sulfolene have been recorded and studied in the solid and liquid states. A vibrational assignment of the observed frequencies is proposed on the basis of the depolarization ratios of the Raman bands and of the dichroic ratios of the i.r. bands.

Inhibiting effect of phosphorus compounds on model transesterification and direct esterification reactions catalysed by titanium tetrabutylate: 2

Abstract The inhibiting effect of phosphorus compounds on the polymerization to poly(butylene terephthalate) catalysed by titanium tetrabutylate was investigated by making use of model molecules. The inhibition, observed on both transesterification and direct esterification reactions, appears only in the presence of acidic OH groups in the phosphorus compounds, which permit the formation of complexes with the Ti atoms of the catalyst. The occurrence of such complexes was confirmed by infra-red spectroscopy.