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We report the results of a combined work based on density functional theory (DFT) calculations and experiments of the factors that influence the glass temperature, T g , and the associated ion conductivity in polymerized ionic liquids bearing imidazolium salts in the side group. This study consists of four different N-alkyl side-chain lengths [with n = 4 (butyl), 6 (hexyl), 8 (octyl), and 10 (decyl)] and seven different counteranionsDFT calculations of the anion−cation complexation energies were combined with thermodynamics (differential scanning calorimetry), structural (X-ray scattering), as well as temperature-and pressure-dependent dielectric spectroscopy measurements of ion conduction. Our results show that ion conduction is facilitated by local anion jumps with a length scale on the order of the charge alteration distance. Ion complexation strongly influences the backbone dynamics and the associated T g . A simple "stick and jump" model can account for the increased backbone mobility (reduced T g ) and the concomitant enhanced ion conductivity for anions with intermediate size. Among the different anions, [TFSI] − with its comparably large size and broad charge delocalization is only weakly coordinated with the cation. This best facilitates anion motion within the "ion paths" of the hexagonally packed cylinders and smectic morphologies.

Single ion conductors, based on polymerized ionic liquids (PILs) with a polythiophene backbone bearing imidazolium salts with butyl, hexyl, octyl, and decyl side groups and six different counteranions ([Br]−, [BF4]−, [ClO4]−, [PF6]−, picrate, and [B­(Ph)4]−), are synthesized and studied with respect to the thermal, structural, and ion-conductivity properties. PILs bearing the polythiophene backbone are unique as they can simultaneously conduct electronic charge and ions at nanometer length scales. In addition, the π–π stacking of the polythiophene backbones results in exceptional smectic-like order. Increasing side group length from butyl to decyl increases the room temperature conductivity by 4 orders of magnitude (internal plasticization). Anion size (anionic radii from 0.19 to 0.44 nm) affects both the structure (from smectic-like to amorphous with increasing anion radius) and the ionic conductivity. Conductivity values differ by 6 orders of magnitude by varying anion size at ambient temperature. As a result, conductivities as high as 2 × 10–3 S/cm could be obtained at high temperatures. Differences in conductivity are discussed in terms of changes in glass temperature (T g), anion size, and value of dielectric permittivity. Overall ion transport in PILs based on polythiophene backbones is controlled by the low T g, value of dielectric permittivity, smectic layering, and ion association lengths not exceeding a single smectic layer.

Densely grafted poly­(ethylene oxide) (PEO) brushes on a poly­(hydroxyl­styrene) (PHOS) backbone (PHOS-g-PEO) as well as block copolymers with polystyrene (PS) (PS-b-(PHOS-g-PEO)) are designed as model systems for Li ion transport. This macromolecular design suppresses the propensity of PEO chains for complex crystal formation with LiTf as well as for crystallization. Li ion conductivities similar or even exceeding those in the archetypal electrolyte poly­(ethylene oxide)/lithium triflate (PEO/LiCF3SO3 (LiTf)) are obtained for a range of temperatures and LiTf compositions. At the same time, PHOS-g-PEO and PS-b-(PHOS-g-PEO) show improved mechanical stability. Typically, at 333 K, the ionic conductivity is ∼6 × 10–5 S/cm and the modulus at ∼2 × 106 Pa for a [EO]:[Li+] = 8:1 composition. In the endeavor for suitable solid polymer electrolytes macromolecular architecture seems to play a decisive role.

The segmental dynamics and the corresponding glass temperature, T g, were investigated in a monocyclic and in the corresponding linear polystyrene as well as in a series of multicyclic polystyrenes, all with the same total molecular weight, with dielectric spectroscopy and DSC. There is a strong reduction of T g with decreasing molecular weight for linear chains but only a moderate reduction for cyclic chains and this below a certain critical molecular weight (M n ∼ 18 000 g/mol). These data contradict the Gibbs–Di Marzio lattice model predicting an increasing glass temperature with decreasing molecular weight of cyclic polymers. In multicyclic polystyrenes the results emphasize the role of constrained segments at the coupling sites (linkers) on determining practically all features of segmental dynamics: the exact temperature dependence of relaxation times and associated T g, the dielectric strength, the distribution of relaxation times, and fragility. A nearly linear increase of T g was found with increasing number of intramolecular constraints. Furthermore, the total molecular weight is an irrelevant parameter in discussing the dynamics of multicyclic polymers. An alternative approach that is based on the concept of free volume emphasizes intermolecular contributions and predicts the same amount of fractional free volume for multicyclic polystyrenes at their respective glass temperature (3.3%) but differences in the respective thermal expansion coefficient of free volume.

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Single-ion-conducting polymer electrolytes (SICPEs) based on polystyrene and poly(ethylene oxide) block copolymers (PS-b-PEO) are promising materials due to the combination of high stability and exclusive charge transport via lithium cations. However, the incorporation of covalently attached anions into the flexible polyether block to yield SICPEs is a synthetic challenge. For this purpose, a polystyrene-b-multifunctional poly(ethylene oxide) block copolymer precursor (M n = 15.1 kg•mol −1 , Đ = 1.09) with randomly distributed multiple hydroxyl functional groups (6% mol ) in the polyether block was synthesized by the combination of living carbanionic and anionic ring-opening polymerization (AROP). First, living polystyryl lithium was endfunctionalized with ethylene oxide (EO). Subsequently, AROP copolymerization of EO and ethoxy vinyl glycidyl ether (EVGE) was initiated by the alkoxide-functional polystyrene macroinitiator, followed by deprotection of the vinyl ether groups. A novel postpolymerization Mitsunobu reaction was developed to quantitatively substitute the hydroxyl groups with tert-butyloxycarbonyl (BOC)-protected trifluoromethanesulfonamide (TFSA) functionalities. The SICPE material was obtained in a following deprotection and deprotonation step of the TFSA groups. All reaction steps were monitored via detailed NMR, IR, and sizeexclusion chromatography (SEC) characterization. The ionic conductivity of the obtained SICPE was compared and contrasted against the established dual-ion conductors PS-b-PEO doped with LiTf and LiTFSI. It was demonstrated to have superior ionic conductivity to PS-b-PEO/LiTf. In addition, the Li-ion conductivity is comparable to the single-ion block copolymer electrolyte poly(ethylene oxide)-b-poly(styrenesulfonyl(lithium trifluoromethylsulfonyl)imide) (PEO-b-PSLiTFSI) within the ordered state.

Discotic liquid crystals based on hexa-peri-hexabenzocoronenes (HBCs) symmetrically substituted with six poly­(ethylene glycol) (PEG) chains and further doped with LiCF3SO3 (LiTf) salt at different [EG]:[Li+] ratios nanophase-separate in domains composed from HBC columns and PEG chains. These model amphiphiles behave as viscoelastic solids with a shear modulus of 5 × 106 Pa and an ionic conductivity of 10–5 S/cm at 373 K. At temperatures below 333 K an ionic superstructure is formed of higher shear modulus (108 Pa) that surrounds the HBC columns and follows the disks in their rotational motion. However, the ionic superstructure impedes ion transport. Substituting the HBC core with two PEG chains breaks the symmetry of the ionic superstructure and increases ionic conductivity by an order of magnitude while retaining a high shear modulus and a viscoelastic response. These findings demonstrate that PEG-functionalized HBCs have great potential as new electrolytes because they combine ionic conductivity with mechanical stability. Moreover, when combined with electronic conduction within the HBC columns, this design can result in structures that exhibit simultaneous electronic and ionic transport.