Multiple Relaxations and Entanglement Behaviors of Polymerized Ionic Liquids with Various Anions/Cations

作者：Gang Liu, Ronald G. Larson, Xi He, Yongjie Dan, Yanhua Niu, Guangxian Li · 发表于：Macromolecules · 年份：2024 · DOI：10.1021/acs.macromol.4c01844 · 被引用次数：6 · 研究领域：Ionic liquids properties and applications、Material Dynamics and Properties、Polymer crystallization and properties

Polymerized ionic liquids (PILs) with anions of bis(trifluoromethylsulfonyl)imide (TFSI – ), hexafluorophosphate (PF 6 – ), and tetrafluoroborate (BF 4 – ) and cations of poly[1-(4-vinylbenzyl)-3- alkyl -imidazolium] P[VBC n IM] + with alkyl lengths C 1, C 2, and C 4 were successfully synthesized and characterized. X-ray scattering showed an increase in backbone-to-backbone spacing ( d b ) by 0.8 Å per CH 2 added to the alkyl side chain. Rheological and dielectric measurements were used to measure rates of chain relaxation and ion dissociation/association. The glass transition temperatures T g follow the trend: PC 4 -TFSI < PC 2 -TFSI < PC 1 -TFSI < PC 1 -BF 4 < PC 1 -PF 6, which correlates well with their dielectric behaviors. However, the fragility m DR from dielectric relaxation increases with decreasing T g, which is the opposite of the dependence of fragility m Rheo from rheology for both our PILs and neutral polymers. The dielectric and rheological relaxations of our PILs are expected to be influenced by both their anion–cation binding energies and their relative free volumes, while for neutral polymers, relaxations are primarily governed by free volume. The increase of fragility of m DR with decreasing T g, therefore, suggests that dielectric relaxation is influenced more by anion–cation binding energy than by free volume, while the reverse is true for m Rheo . The plateau modulus G N and entanglement molecular weight M e estimated from rheological measurements agree w...