Dielectric spectroscopy was used to determine the static dielectric constants (ε s ) of imidazolium acrylates and methacrylates and their ionomers, with different imidazolium pendant structures containing a combination of alkylene [(CH 2 ) n , n = 5 or 10] and ethyleneoxy [(CH 2 CH 2 O) n , n = 4 or 7.3 (the average of a mixture of n = 1 to 20)] units as spacers between the backbone and the imidazolium cation. All monomers and polymers exhibited two dipolar relaxations, assigned to the usual segmental motion (α) associated with the glass transition and a lower frequency relaxation (α 2 ), attributed to ions rearranging. From the analysis of the static dielectric constants using the Kirkwood g correlation factor, the dipoles in conventional (smaller) ionic liquids prefer antiparallel alignment (g ≈ 0.1), lowering ε s values (≤30), because their polarizability volumes V p strongly overlap, whereas the dipoles in the larger ionic liquid monomers display g of order unity and 50 ≤ ε s ≤ 110. A longer spacer leads to higher static dielectric constant, owing to a significant increase of the relaxation strength of the α 2 process, which is directly reflected through an unanticipated increase of the static dielectric constant with ionic liquid molecular volume V m . The glass transition temperature of polymerized imidazolium ionic liquids with various counterions is also shown to simply be a monotonically decreasing function of V m . Furthermore, the ionomers consistently exhibit 1.5−2.3 times higher static dielectric constants (ε s up to ∼140 at room temperature) than the monomers from which they were synthesized, suggesting that polymerization encourages the observed synergistic dipole alignment (g > 1).

No abstract

Five new bis(dibenzo-30-crown-10-based cryptand)s were synthesized, two of which (16 and 17) had long (12-atom), flexible spacers that led to cooperative complexation of dibenzyl paraquat TFSI ( K = 4.36 × 10 M for 17•2b). Self-assembly of 16 and 17 with bisparaquats with similar spacers (18, 21, and 23) led to high molecular weight supramolecular pseudorotaxane polymers in solution. Continuous, flexible fibers were drawn from concentrated solutions. 17 with C-linked bisparaquat 23 in dichloromethane (DCM) produced a log-log viscosity vs concentration plot with a limiting slope of 3.55, confirming high molecular weight; at 37 mM, the degree of polymerization was estimated to be 126 and M = 407 kDa. These are the first truly polymeric pseudorotaxane-type AA/BB supramolecular polymers.

Ion transport and segmental dynamics were studied for one- and two-armed norbornene ionic liquid monomers (ILMs) including imidazolium (Im+)-bis­(trifluoromethanesulfonyl)­imide (Tf2N–) pairs, with different imidazolium pendant structures containing either alkylene [(CH2)2] or oxyethylene [(OCH2CH2) x =(OE) x , x = 1, 2, or 3] units as the linkers between the norbornene and the imidazolium cation, using dielectric relaxation spectroscopy and oscillatory shear. All ILMs exhibit three dipolar relaxations, assigned to the fastest frequency glassy β relaxation, attributed to local chain motions of pendant groups, the intermediate frequency segmental α relaxation, associated with the glass transition (T g), and the slowest frequency ionic α2 relaxation, attributed to ions rearranging; the former has an Arrhenius character, while the latter two have Vogel temperature dependences. The incorporation of the OE linkers lowers the glass transition temperature (T g), accelerating the α and α2 relaxations, and increases the static and Coulombic dielectric constants (εs after the α2 relaxation and εC between the α and α2 relaxations), compared to the monomer without the OE linker. From the analysis of εs using the Onsager theory, the one-armed norbornene ILM εs is well predicted, but the two-armed ILMs exhibit lower experimental εs values compared to the Onsager prediction. This suggests that there is more ionic aggregation in the two-armed ILMs due to strongly overlapping polarizability volumes, consistent with the Kirkwood g correlation factor less than unity and higher polarizability volume overlap parameter, indicating that Im+Tf2N– ion pairs are strongly interacting and preferring an antiparallel alignment, thereby lowering εs. Furthermore, εC increases with the OE x linker length, consistent with Landau and Lifshitz’s mixing rule, revealing that with higher OE content, the environment is more polar for the ionic dissociation of the Im+Tf2N– ion pairs. This is directly reflected in ionic conductivities (σDC), which are strongly correlated with both T g and εC.

Norbornene-based polymerized ionic liquids (PILs) were systematically prepared to understand the role of PIL architecture and linker on the ionic conductivity (σ DC ), segmental dynamics, and dielectric constant. In PILs with two-or one-armed imidazolium (Im + )-bis(trifluoromethanesulfonyl)imide (Tf 2 N − ) pendants, their dynamics and polarity were tuned by incorporating either oxyethylene [(OCH 2 CH 2 ) x = (OE) x , x = 1 or 3] or alkylene [(CH 2 ) 2 ] moieties as linkers between the norbornene and imidazolium cation moieties and ethyleneoxy [(CH 2 CH 2 O) y = (EO) y , y = 2 or 3] terminal units on the imidazolium. All PILs exhibit three dipolar relaxations; the local chain β motions of the PIL pendants were observed below the glass transition temperature (T g ), while above T g , the segmental α and slower ionic rearranging α 2 relaxations were observed. Unlike the alkylene linker, the OE linker incorporation speeds up the α and α 2 relaxations (consistent with the decrease in T g ), increases the relaxation strengths [leading to an increase in the static and Coulombic dielectric constants (ε s and ε C )], imparts a higher number density of simultaneously conducting ions (p), and boosts their mobility (μ). This is directly reflected in the OE-containing PILs having 10 times higher ionic conductivities (σ DC ) than the PIL with the alkylene linker. The T g , ε s , and σ DC are significantly influenced by the repeat unit molecular volume (V m ), polarizability volume (V p ), and Keesom volume (V K ), suggesting that the OE linker not only facilitates ion dissociation of Im + Tf 2 N − but also promotes segmental motion, thereby leading to a strong correlation of ionic conductivity with the dielectric constant and glass transition temperature.