Dielectric Relaxation and Rheological Behavior of Supramolecular Polymeric Liquid

Abstract

A model self-complementary supramolecular polymer based on thymine and diamidopyridine triple hydrogen-bonding motifs has been synthesized, and its dielectric and rheological behavior has been investigated. The formation of supramolecular polymers has been unequivocally demonstrated by nuclear magnetic resonance, electrospray ionization mass spectrometry with traveling wave ion mobility separation, dielectric spectroscopy, and rheology. The dynamical behaviors of this associating polymer generally conform to those of type-A polymers, with a low-frequency chain relaxation and a high-frequency α relaxation visible in both rheological and dielectric measurements. The dielectric chain relaxation shows the ideal symmetric Debye-like shape, resembling the peculiar features of hydrogen-bonding monoalcohols. Detailed analysis shows that there exists a weak decoupling between the mechanical terminal relaxation and dielectric Debye-like relaxation. The origin of the Debye-like dielectric relaxation is further discussed in the light of monoalcohols.

Communication: Slow supramolecular mode in amine and thiol derivatives of 2-ethyl-1-hexanol revealed by combined dielectric and shear-mechanical studies

“…49 A crossover from an intermediate to the terminal power law reported for shortchain polymers, polymeric liquids, or monoalcohols (ν 0.7 ) is an evidence of an additional slow supramolecular organization/dynamics. [23][24][25]42,50 In the present study, due to resolution limits of the PSG technique, we were not able to clearly observe the change of the frequency dependence of G ′ and G ′′ at modulus values lower than 1 MPa. However, the power law of the lowfrequency part of the mechanical loss shear spectra for amine (ν 0.85 ) and thiol (ν 0.93 ) shows that they display an intermediate behavior between the one reported for non-associating and associating liquids.…”

“…[32][33][34][35][36][37][38][39] 27 The slow supramolecular mode has been mainly documented for monoalcohols but very little studied for other types of hydrogen bonding liquids. 42,43 However, supramolecular hydrogen bonding structures can potentially be created by halogens, amines, and perhaps thiols as well. Their effective strength is expected to decrease in the same order as the difference in electronegativity of the constituting atoms.…”

Communication: Supramolecular structures in monohydroxy alcohols: Insights from shear-mechanical studies of a systematic series of octanol structural isomers

“…This spectral feature is interpreted to originate from the same supramolecular structures responsible for the dielectric Debye process, and is identical to what is observed for short chain polymers. 21,22 Furthermore, it has been shown that also nuclear magnetic resonance, 17 dynamic light scattering, 3 and quasi-elastic neutron scattering 23 are sensitive to the Debye-process and similar results have been seen in mechanical studies of supramolecular polymers 1 and high temperature alcohols.…”

“…Liquids forming supramolecular structures are currently receiving a great deal of attention. [1][2][3][4][5] In this Communication, we present shear-mechanical spectroscopy results on monohydroxy alcohols (i.e., alcohols containing only a single OH group). A monohydroxy alcohol is one of the simplest systems showing pronounced formation of supramolecular structures and has been studied intensively in the past mainly by dielectric spectroscopy (dating back 100 years), but also by xray and neutron scattering, and calorimetry (see recent extensive review by Böhmer et al 5 and earlier compilation of classical results (Sec.…”

“…17-19. Until recently, it was commonly accepted that the process leading to the Debye-peak only showed a signature in dielectric spectroscopy, what lead to many speculative arguments for why a signal was absent in, e.g., shear-mechanics and specific heat. 1,5,20 This conventional belief was challenged, however, when Gainaru et al 4 very recently demonstrated the existence of a shear-mechanical low-frequency feature in the spectra of two monohydroxy alcohols (2-ethyl-1-hexanol and 4-methyl-3-heptanol) close to the glass-transition temperature. Applying two high resolution shear-mechanical techniques enabled an identification of a low-frequency (i.e., sub alpha peak-frequency) crossover from an intermediate behavior to a terminal viscous behavior.…”