Imidazolium Polyesters: Structure–Property Relationships in Thermal Behavior, Ionic Conductivity, and Morphology

Abstract

New bis(ω‐hydroxyalkyl)imidazolium and 1,2‐bis[N‐(ω‐hydroxyalkyl)imidazolium]ethane salts are synthesized and characterized; most of the salts are room temperature ionic liquids. These hydroxyl end‐functionalized ionic liquids are polymerized with diacid chlorides, yielding polyesters containing imidazolium cations embedded in the main chain. By X‐ray scattering, four polyesters are found to be semicrystalline at room temperature: mono‐imidazolium‐C11‐sebacate‐C6 (4e), mono‐imidazolium‐C11‐sebacate‐C11 (4c), bis(imidazolium)ethane‐C6‐sebacate‐C6 (5a), and bis(imidazolium)ethane‐C11‐sebacate‐C11 (5c), all with hexafluorophosphate counterions. The other imidazolium polyesters, including all those with bis(trifluoromethanesulfonyl)imide (TFSI−) counterions, are amorphous at room temperature. Room temperature ionic conductivities of the mono‐imidazolium polyesters (4 × 10−6 to 3 × 10−5 S cm−1) are higher than those of the corresponding bis‐imidazolium polyesters (4 × 10−9 to 8 × 10−6 S cm−1), even though the bis‐imidazolium polyesters have higher ion concentrations. Counterions affect ionic conduction significantly; all polymers with TFSI− counterions have higher ionic conductivities than the hexafluorophosphate analogs. Interestingly, the hexafluorophosphate polyester, 1,2‐bis(imidazolium)ethane‐C11‐sebacate‐C11 (5c), displays almost 400‐fold higher room temperature ionic conductivity (1.6 × 10−6 S cm−1) than the 1,2‐bis(imidazolium)ethane‐C6‐sebacate‐C6 analog (5a, 4.3 × 10−9 S cm−1), attributable to the differences in the semicrystalline structure in 5c as compared to 5a. These results indicate that semicrystalline polymers may result in high ionic conductivity in a soft (low glass tranition temperature, Tg) amorphous phase and good mechanical properties of the crystalline phase.

Covalently crosslinked 1,2,4-triazolium-containing polyester networks prepared by Michael addition polymerization

“…Lower T g values were observed for polymers 9 and 10 where the larger [OTf] and [NTf 2 ] anions were employed. The correlation between anion size (network packing) and T g is supported by work previously published by our group as well as by Gibson and could be the result of plasticization and/or ionic interactions [41,42,47]. As expected, an increase in acrylate concentration resulted in an increase in T g for the polymer series 10aee due to the generation of a more highly crosslinked network.…”

Combined main-chain/side-chain ionic liquid crystalline polymer based on ‘jacketing’ effect: Design, synthesis, supra-molecular self-assembly and photophysical properties

“…Because residual water was present in the sample, the stretching for Br" could not be discerned from the FTIR spectrum. Both the NMR and FTIR results were in good agreement with data found in the literatures [53,54]. To recap, the combination of 1 H NMR and FTIR experiments demonstrated that the ionic liquid crystals side chain monomers with different anions were successfully prepared and the anionexchange step was successfully achieved.…”

Molecular Volume Effects on the Dynamics of Polymerized Ionic Liquids and their Monomers

“…The ILs examined here exhibit glass transition temperatures between À120 and À75 C with 0.2 nm 3 < V m < 0.5 nm 3 and have lower T g than the alkali inorganic salts [55] with lower V m . Moreover, imidazolium and other organic IL cations can be synthesized with either vinyl, acryl or methacryl groups so that the IL monomers (substituted with polymerizable functional groups) can be easily polymerized to create PILs, which carry an ionic liquid species in each of the repeating units [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36]. Fig.…”