Dielectric Relaxation in Hydrogen Bonded Urea-Based Supramolecular Polymer N,N'-di(2,2-dipentylheptyl)urea

Abstract

Results of the dielectric relaxation studies, performed for supramolecular polymer formed by N, N-di(2,2-dipentylheptyl)urea dissolved in carbon tetrachloride, are presented. The measurements were done for N, N-di(2,2-dipentylheptyl)urea concentration up to about 7% (in mole fraction) in the frequency region from 100 kHz to 100 MHz and at the temperatures from 5 • C to 50 • C. The analysis of the experimental data were performed with the Havriliak-Negami equation. In the studied range of N, N-di(2,2-dipentylheptyl)urea concentration and temperature, the obtained values of exponents α and β of the Havriliak-Negami equation are equal to 0.9 ± 0.1 and 0.7 ± 0.1, respectively, showing an anomaly in the dielectric relaxation behavior close to the Davidson-Cole type. Two examples of the modeling of dielectric properties of the supramolecular polymer solutions were presented.

Molecular Dynamics and Entropy Effects in Hydrogen-Bonded Supramolecular PolymerN,N′-Di(2-methyl-2-pentylheptyl)urea Dissolved in Nonpolar Medium

“…The anomaly recorded in the dielectric relaxation behavior of the supramolecular polymer studied here is of the Davidson−Cole type (α ≈ 1, 0 < β < 1), , and the behavior is similar to that observed for other N , N ′-dialkylureas with a large alkyl substituent . The dependences obtained for the fractional exponent β (Figure ), representing the extent of the Davidson−Cole type anomaly in the dielectric relaxation spectra, clearly show that both with increasing the urea concentration (at constant temperature) and decreasing temperature (at constant concentration) the value of the exponent β increases.…”

“…43 The dependences obtained for the fractional exponent ( Figure 5), representing the extent of the Davidson-Cole type anomaly in the dielectric relaxation spectra, clearly show that both with increasing the urea concentration (at constant temperature) and decreasing temperature (at constant concentration) the value of the exponent increases. This indicates that with increasing degree of the molecular self-assembly the relaxation spectra become more and more close to the Debye pattern ( ) 1).…”

Hydration and self-aggregation of a neutral cosolute from dielectric relaxation spectroscopy and MD simulations: the case of 1,3-dimethylurea

“…To estimate the dynamics of the H-bonds between appropriate particles/sites we also calculated corresponding H-bond lifetimes, t H . As urea derivatives are prone to self-aggregation, 70,[81][82][83][84] the contact times and H-bond lifetimes between neighboring 1,3-DMU molecules were also calculated. To do so, we define an aggregate existence correlation function C(t) as…”

Structural and AC electrical properties study of solid metal urea complexes

“…19 The band at 1470 cm À1 in urea is assigned to the N-C-N stretching vibration which shifts to the band (1473-1534 cm À1 ) in urea complexes. As a result, a double bond between the carbon and nitrogen is formed in the complexes 26 and thus the wavenumber increases. As a representative example, Fig.…”

“…Upon surveying, most available studies are mainly focused on the static dielectric measurements carried out on urea in aqueous solutions. [24][25][26][27] Till now, no published work is available for correlating AC measurements with the molecular structure of solid urea and its complexes, namely: U, Co(U) 6 Cl 2 , Cu(U) 6 Br 2 and Ni(U) 6 Br 2 . Therefore, in the current study, AC measurements have been carried out on the solid urea complexes in order to find a correlation between the samples' dynamic molecular behavior and their molecular structure.…”