Alkyl‐Substituted N‐Vinylimidazolium Polymerized Ionic Liquids: Thermal Properties and Ionic Conductivities

Abstract

Structure-property relationships for polymerized ionic liquids (PILs) relate chemical structure to ionic conductivity and reveal the importance of glass transition temperature ( T g ) and the energy associated with an ion-hopping mechanism for ion conduction for a series of alkyl-substituted vinylimidazolium PILs. The alkyl-substituted vinylimidazolium-based PILs with varying lengths of n -alkyl substituents provide diverse precursors with exchangeable anions to further enhance thermal stability and ionic conductivity. As the anion size increases, regardless of alkyl substituent length, T g decreases and the onset of weight loss, T D , increases. As the length of the alkyl substituent increases, T g decreases for PILs with Br − and BF 4 − counteranions. Ionic conductivity increases over an order of magnitude upon exchange of the counteranion from TfO − < Tf 2 N − . due to their unique combination of physical properties including high thermal stability, wide electrochemical window, negligible vapor pressure, and potentially high ionic conductivities. [3][4][5][6][7] Two particular classes of ILs are polymerizable ILs (PILs) that contain polymerizable functional groups and room temperature ILs (RTILs) with melting temperatures at or below room temperature. [ 8 ] Potential applications have included electrolytes in electromechanical transducers, artifi cial muscle fabrication, and non-volatile solvents for a myriad of chemical reactions. [ 9 ] Chen and Elabd investigated the solution properties and subsequent formation of electrospun fi bers of an imidazolium-containing methacrylate-based PIL. [ 10 ] This study revealed solution properties similar to polyelectrolyte solutions, and electrospun fi bers formed with intermediate fi ber diameters and onset of fi ber formation between polyelectrolyte and neutral polymers. The fi brous mats exhibited promising ionic conductivities at room temperature, and upon swelling with a RTIL, ionic conductivities were on the order of 10 mS cm − 1 . Long and co-workers also investigated the impact of counteranion on the solution and thermal properties of ammoniumbased polyelectrolytes. [ 11 ] Our study revealed the important infl uence of anion selection on the T g of the polyelectrolyte, and we observed polyelectrolyte electrospinning

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.…”

Ion transport in sulfonated polymers

“…Extensive research by various groups has established that the use of ionic salts, that is, ILs, composed of heterocyclic diazoles and counter-ions, can substantially improve the transport properties of sulfonated PEMs since the degree of ion dissociation, local concentration of ions, and T g of the membranes can be manipulated. [81][82][83][84] Such manipulations should also cause a large alteration in the thermodynamic properties of the PEMs, leading to an increasing number of fundamental studies on the thermodynamics of ILs-containing sulfonated PEMs. 46 For IL-incorporated sulfonated PEMs, the key factors governing the anhydrous transport properties should be the type of ILs (cations and anions) and the amounts of ILs within the PEMs.…”

Well‐Defined Imidazolium ABA Triblock Copolymers as Ionic‐Liquid‐Containing Electroactive Membranes

“…Tuning ABA triblock composition enables tailored charge content, mechanical properties, and morphology . The interplay between glass transition temperature ( T g ) and ionic conductivity is firmly described in the literature, and recent studies focused on the influence of diblock copolymer morphology on ionic conductivity .…”