Abstract
The structure and dynamics of pure and mixed liquid aromatic esters is studied through microwave dielectric relaxation spectroscopy in the 200 MHz – 20 GHz frequency range. Methyl, ethyl, propyl and butyl benzoate were studied at 298.15 K to infer the alkylic chain length effect on solvents properties showing that the relaxational behaviour for the four esters is properly described with a single Debye type function for the considered range. Methylbenzoate behaviour was also analyzed in the 278.15 – 358.15 K temperature range to study the temperature effect on their properties. Experiments on phenyl acetate were carried out to analyze the effect of aromatic ring position on fluid structure. We have also considered the properties at 298.15 K of different methylbenzoate containing mixed fluids with n-hexane, cyclohexane, 1-chlorohexane, 1-hexanol, hexanoic acid and diisopropyl ether to study the effect of different functional groups on fluid structure upon mixing. All the binary mixtures studied are properly described using a bimodal Debye process in the whole composition range. Data are analyzed in terms of the proposed different species present in the fluids and their evolution with composition for mixtures, and with temperature and chain length for pure esters. PAC CODES: 77.22.Gm, 61.25.Em, 34.20.Gj
Highlights
Dielectric relaxation spectroscopy, DRS, is a powerful tool to elucidate the structure and dynamics of complex fluids because in many cases offers unique information on these systems [1]
Previous experimental and theoretical results have showed the complexity of aromatic esters fluids structure, in pure or mixed states, which is governed by several factors: i) their almost planar shape, decreasing with increasing alkylic chain length, ii) their dipolar character and iii) their ability to act as hydrogen bonding acceptors with several compounds through the carbonyl oxygen of the molecules [5,6,7,8,9,10,11]
These results show the importance of the interaction among phenyl and carbonyl group in the aromatic esters fluid structure, the effect of the aromatic ring position with respect to the ester group in the molecule was inferred from the comparison of MB and PA results
Summary
Dielectric relaxation spectroscopy, DRS, is a powerful tool to elucidate the structure and dynamics of complex fluids because in many cases offers unique information on these systems [1]. In order to get a deeper insight into the liquid structure of this group of fluids, we report here a DRS study in the microwave frequency range; according to these experimental results, a better knowledge on their structure and dynamics should be gained, from which a complete picture of the facts that govern their behaviour may be obtained, completing our previous studies. This is the first DRS study on aromatic solvents to the best of our knowledge
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