Chain Dynamics of Ethylene Oxide Oligomer Melts. An Ultrasonic Spectroscopy Study

Abstract

Between 0.2 and 2000 MHz, the ultrasonic attenuation spectra of oligomer melts have been measured at 25 °C. The oligomers comprise ethylene glycols with eight different mean degrees [Formula: see text]of polymerization (1 ≤ [Formula: see text] ≤ 13.2), a poly(propylene glycol) ([Formula: see text] = 16.9) and three poly(ethylene glycol) dimethyl ethers (3 ≤ [Formula: see text] ≤ 10.3). The complexity of the ultrasonic spectra increases with [Formula: see text]. The spectra have been analyzed assuming up to four discrete relaxation terms. The relaxation times of these terms are assigned to the first odd modes in the oligomer conformational dynamics and are discussed in the light of the Rouse spring-and-dashpot and the Tobolsky torsional oscillator models of chain variations. The relaxation amplitudes indicate that not only the shear viscosity but also the volume viscosity is involved in ultrasonic relaxation processes. Comparison of relaxation times and shear viscosities for the ethylene glycols with the corresponding data for dimethyl ethers and also n-alkanes reveals significant effects of association.

Ultrasonic Relaxation Study of 1-Alkyl-3-methylimidazolium-Based Room-Temperature Ionic Liquids: Probing the Role of Alkyl Chain Length in the Cation

“…Fortunately, from the ultrasound absorption data, the frequency dependence of the ultrasonic velocity can be estimated. 55,59,60 Figures 8 and 9 show examples of the ultrasonic velocity dependence on frequency estimated from the absorption data by use of the following relation…”

“…Because of the relatively large ultrasonic absorption in many RTILs, ultrasonic velocity is subject to a considerable dispersion. Fortunately, from the ultrasound absorption data, the frequency dependence of the ultrasonic velocity can be estimated. ,, Figures and show examples of the ultrasonic velocity dependence on frequency estimated from the absorption data by use of the following relation where A i and f rel, i denotes the parameters obtained from the ultrasound absorption data. The n number is the same as in the case of the model used for description of the ultrasound absorption data, i.e., the use of eq (single Debye term) leads also to n = 1 in eq .…”

“…Fortunately, from the ultrasound absorption data, the frequency dependence of the ultrasonic velocity can be estimated. 55,59,60 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 Finally, we must explain that only originally calculated sets of parameters of ultrasound absorption spectra were discussed because of the small effect on these spectra resulting from consideration (or not) of the ultrasound dispersion. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 33 …”

Speed of Sound and Ultrasound Absorption in Ionic Liquids

“…[49][50][51] Alternative include ultrasound absorption measurements and the indirect estimation of the dispersion because a functional relationship exists between α⋅f -2 data and u(f). 52,53 For ILs, such investigations are well-founded and desirable because many ILs under defined conditions can undoubtedly be classified as dissipative or even strongly dissipative liquids because of their high and very high viscosities (the viscosity values of most ILs are 2-3 orders of magnitude larger than typical molecular organic solvents). To our knowledge, the dispersion of ultrasound velocity has only been directly studied on a limited scale in some ILs with the transient grating method.…”

Reorientational Relaxation of Small Solutes in Viscoelastic Liquids

“…In addition, benzene is chosen as a reference liquid, and ethylene glycol is employed because the mechanical relaxation spectrum was already determined in the GHz region using longitudinal ultrasonic spectroscopy. 29 The solute concentration was 1 wt % for NMR measurement except in cases of biphenyl in squalane, dibutyl phthalate and ethylene glycol, and p-terphenyl in polydimethylsiloxane-20 cSt, squalane, and dibutyl phthalate. The measurements on these solutions were performed at the saturated concentration which was lower than 1 wt %.…”