The linear viscoelastic (LVE) and dielectric relaxation spectroscopic (DRS) properties of polysiloxanes with phosphonium (fraction f) and oligo(ethylene oxide) (fraction 1 – f) side groups with a fraction of ionic monomers f = 0–0.26 have been studied. LVE master curves of those ionomers have been constructed. The ionic dissociation has been witnessed as a delayed polymer relaxation in LVE with increasing ion content, as well as an α2 ionic segmental relaxation process in DRS. LVE exhibits glassy and delayed rubbery relaxation at low ionic fraction f ≤ 11%, where the ionic dissociation time detected in DRS enables description of LVE with a sticky Rouse model. In contrast, the glassy and rubbery stress relaxation moduli merge into one broad process at high f ≥ 22%, where the whole LVE response from glassy to terminal relaxation can be described phenomenologically by a single Kohlrausch–Williams–Watts (KWW) equation with the lowest stretching exponent β = 0.10 ever seen for polymeric liquids, describing LVE over 15 decades of frequency.

Polysiloxane phosphonium single-ion conductors grafted with oligomeric PEO and with ion contents ranging from 5 to 22 mol % were synthesized via hydrosilylation reaction. The parent Br − anion was exchanged to F − or bis-(trifluoromethanesulfonyl)imide (TFSI − ). X-ray scattering data suggest ion aggregation is absent in these phosphonium ionomers, which contributes to low glass transition temperatures (below −70 °C) with only a weak dependence on both ion content and counteranion type. Conductivities weakly increase with ion content but exhibit a strong dependence on anion type. The highest conductivity at 30 °C is 20 μS/cm for dry neat ionomer, with the TFSI − anion, consistent with its relatively delocalized negative charge and large size that weaken interactions between TFSI − and the phosphonium cation.

Fourier transform infrared spectroscopy (FTIR) and linear viscoelasticity (LVE) were used to characterize amorphous copolyester ionomers synthesized via condensation of sulfonated phthalates with mixtures of poly(ethylene glycol) with M = 600 g/mol and poly(tetramethylene glycol) with M = 650 g/mol. The copolymer ionomers exhibited microdomain separation, as confirmed in previous X-ray scattering measurements. Since PEO has superior ion solvating ability compared with PTMO, the ions near the interface reside preferentially in the PEO microdomain. FTIR measurements were used to quantify fractions of ions in different association states, in turn quantifying the fractions in the PEO-rich domains, in the PTMO-rich domains, and at the interface between these domains. FTIR shows that the structure of the interfacial ion aggregates is quite different for the copolymers with different counterions; at the interface Na+ aggregates into open string structures while Li+ aggregates into denser sheets of ions, as depicted schematically at the far right. Ionic conductivity is dominated by ions in the PEO domain, due to superior cation solvation by PEO; in the PTMO-rich microdomain both Na+ and Li+ form dense aggregates with of order 15 ion pairs. The temperature dependence of viscoelastic properties depends primarily on the PEO segmental dynamics, due to much higher T g for the PEO-rich microdomains that are continuous at all copolymer compositions studied. Increasing the PTMO fraction increases the ionic association lifetime and delays the LVE terminal relaxation, creating an extended rubbery plateau, despite the fact that the chains are quite short.

A quantum-mechanical investigation on Li poly(ethylene oxide)-based ionomers was performed in the cluster-continuum solvation model (CCM) that includes specific solvation in the first shell surrounding the cation, all surrounded by a polarizable continuum. A four-state model, including a free Li cation, Li(+)-anion pair, triple ion, and quadrupole was used to represent the states of Li(+) within the ionomer in the CCM. The relative energy of each state was calculated for Li(+) with various anions, with dimethyl ether representing the ether oxygen solvation. The population distribution of Li(+) ions among states was estimated by applying Boltzmann statistics to the CCM energies. Entropy difference estimates are needed for populations to better match the true ionomer system. The total entropy change is considered to consist of four contributions: translational, rotational, electrostatic, and solvent immobilization entropies. The population of ion states is reported as a function of Bjerrum length divided by ion-pair separation with/without entropy considered to investigate the transition between states. Predicted concentrations of Li(+)-conducting states (free Li(+) and positive triple ions) are compared among a series of anions to indicate favorable features for design of an optimal Li(+)-conducting ionomer; the perfluorotetraphenylborate anion maximizes the conducting positive triple ion population among the series of anions considered.

Anion conducting polyphosphazene ionomer analogues of poly[bis(methoxyethoxyethoxy)phosphazene] (MEEP) were synthesized and their iodide transport properties studied. Polymer bound cations were quaternized with either short alkyl or short ether oxygen chains. X-ray scattering reveals a low q peak near 4 nm −1 arising from the backbone−backbone spacing between polyphosphazene chains, an ion-related peak at 8 nm −1 , and a peak at 15 nm −1 corresponding primarily to the amorphous halo of the PEO side chains. Because of the short spacing of the intermediate q peak, the ions are proposed to exist mostly in isolated ion pairs or small aggregates. First-principles calculations combined with dielectric spectroscopy suggest that less than 10% of the ions are in isolated pairs while the remainder participate in quadrupoles or other small aggregates. These ionomers display high values for the high frequency dielectric constant, ε ∞ (highest value ε ∞ = 11), due to atomic polarization of the iodide anion. These MEEPbased ionomers have room temperature dc conductivity of order 10 −6 S cm −1 and show potential for application in iodide conducting solar cells if the segmental mobility could be increased.