Imidazole Polymers Derived from Ionic Liquid 4-Vinylimidazolium Monomers: Their Synthesis and Thermal and Dielectric Properties

Abstract

The synthesis of 1-ethyl-3-methyl-4-vinylimidazolium triflate, its polymerization, and ion exchange to yield a family of 4imidazolium polymers with a variety of anions are described. For comparative purposes, the synthesis, polymerization, and ion exchange of an analogous set of 1-vinylimidazolium polymers are also presented. The comparative thermal and dielectric characteristics of the 4-vinyland 1-vinylimidazolium salts were evaluated. The trends in the glass transition (T g ) characteristics of the various 4-vinylimidazolium and 1vinylimidazolium polymers were similar; however, the glass transition temperatures of poly( 4-vinylimidazolium) BF 4 − , PF 6 − , AsF 6 −, and CF 3 SO 3 − salts were significantly higher than those of the corresponding poly(1-vinylimidazolium) salts. This difference and the increase in T g in going from BF 4 − to AsF 6 − in the 4-vinylimidazolium series were attributed to enhanced intramolecular bridging between imidazolium moieties positioned 1,3 or 1,5 along the polymer chain. In the dielectric spectra of 1-vinylimidazolium salts at temperatures in excess of 30 °C, one relaxation mode distinct from that for electrode polarization is observed. The single mode appears to correspond to the α-relaxation peak in poly(3-ethyl-1-vinylimidazolium salts) recently identified and attributed to ion-pair motion by Nakamura et al. In the 4-vinylimidazolium polymer spectra set, at temperatures in excess of 30 °C, two relaxation modes, distinct from that for electrode polarization, are apparent: the α peak also observed in the 1-vinylimidazolium polymer set and a new relaxation peak observed at lower frequency. The lower frequency relaxation peak is identified in this work as the α′-relaxation and is also associated with ion-pair motion. Assuming the relaxation processes to be Arrhenius in nature, the activation energy of the α-relaxation in poly(4-vinylimidazolium) BF 4 − , PF 6 − , CF 3 SO 3 − , TFSI − , and C 2 N 3 − salts ranged from 83 to 28 kJ/mol and appears to scale with the glass transition temperature.

Visible‐Light‐Mediated Addition of α‐Aminoalkyl Radicals to [60]Fullerene by Using Photoredox Catalysts

“…In these immobilized salts, the IL cation is normally linked through the charged nitrogen atom. The synthesis of C ‐functionalized imidazolium monomers requires quite complex strategies 42. In contrast, C ‐vinyl‐functionalized triazoles can be easily obtained by a one‐step copper‐catalysed azide–alkyne [2+3] Hüisgen addition reaction43 and, after quaternization and metathesis reaction, the initially formed IL monomer can be readily polymerized by free‐radical reactions.…”

Anomalous Thermal Characteristics of Poly(ionic liquids) Derived from 1-Butyl-2,3-dimethyl-4-vinylimidazolium Salts

“…In our research, we focused on 4-vinylimidazolium polymers [33]. The molecular structure of a pentad segment of a 4-vinylimidazolium polymer is shown in Figure 1.…”

“…This difference, and the increase in Tg of P4VIm + salts of complex fluoride As compared to the more widely studied 1-vinylimidazolium polymers [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][34][35][36][37], the pendant imidazolium group in 4-vinylimidazolium polymers can exhibit additional degrees of freedom, increased free volume, and enhanced lateral overlap between proximate imidazolium residues that may be situated 1,3 or 1,5 with respect to each other on the carbon chain. Work from our laboratory on the synthesis, thermal characteristics, and dielectric properties of poly(ionic liquids) derived from 1,3-dialkyl-4-vinylimidazolium salts presented data on the comparative thermal and dielectric characteristics of the 4-vinyl and 1-vinylimidazolium salts [33]. In that work, it was shown that the glass transition characteristics of 4-vinyl-and 1-vinylimidazolium salts are similar, with the glass transition temperatures of P4VIm + [poly(1-ethyl-3-methyl-4-vinylimidazolium)], BF 4 − , PF 6 − , AsF 6 − , and Tf − salts being higher than those of the corresponding poly(1-vinylimidazolium) salts.…”

Structural Characterization and Thermal Properties of Chiral Poly(amide-imide)/Modified MgAl Layered Double Hydroxide Nanocomposites Prepared via Solution Intercalation

“…Recently molten tetrabutyl ammonium bromide (TBAB) was used as a green solvent for the preparation of PAIs [40] . Ionic liquids (ILs) are frequently considered as green solvents due to their small vapor pressure and other properties, such as excellent ability to dissolve organic compounds, salts and metals, facile recyclabilities non-flammability and high temperature stability [41][42][43] .…”