Periodic Polyethylene Sulfonates from Polyesterification: Bulk and Nanoparticle Morphologies and Ionic Conductivities

Abstract

A series of polyethylene-like ionomers with periodic sulfonate groups were synthesized by polyesterification of octatetracontane-1,48-diol and tetrabutylammonium dimethyl sulfosuccinate. Optional cation exchange in aqueous dispersions replaced the NBu4 + counterions for Na+ or Cs+. The defined periodic microstructure of the polymers leads to the formation of layered structures in bulk and to platelet-like self-stabilized nanoparticles in aqueous dispersion, as observed by X-ray scattering and transmission electron microscopy. The bulk polymers exhibit a semicrystalline structure with multiple stacks of ionic layers embedded in the crystallites with a layer-to-layer distance of 50–60 Å. Upon melting, the ionic layers in the NBu4 +-neutralized polymer transitioned to disordered ionic aggregates, while the layered ionic aggregates in the Cs+- and Na+-neutralized polymers transformed into ionic aggregates with hexagonal symmetry, which is an unprecedented order-to-order transition in microphase-separated ionomers and a direct result of the molecular periodicity in these polymers. The ionic conductivities depend on the ionic aggregate morphologies. When ionomers are semicrystalline and have layered aggregates, the ionic conductivity is decoupled from the polymer segmental motion and increases with the cation size (Na+ < Cs+ < NBu4 +). These new periodic polyethylene sulfonates produce a variety of ionic aggregate morphologies with good connectivity that can be further manipulated to improve ion dissociation and increase ionic conductivity.

Sub-3-Nanometer Domain Spacings of Ultrahigh-χ Multiblock Copolymers with Pendant Ionic Groups

“…The number of repeating units ( n ) of the PES x Li multiblock copolymers was determined by the end group analysis of 1 H NMR signals (Figures S2 and S3): n = 55 for PES12Li and n = 17 for PES18Li. Note that the value of n is proportional to the total molecular weights of PES x Li polymers and remains constant during the cation exchange of the polymers …”

“…Ion-containing polymer systems are a promising strategy for preparing high-χ multiblock copolymers, because the presence of ionic groups effectively increases the segregation strength between the blocks. ,− For example, our previous studies examined the phase behaviors of polyethylene-based sodium sulfosuccinate (PES x Na) multiblock copolymers, which contain short polar blocks with pendant Na + SO 3 – groups and nonpolar polyethylene blocks of x carbons ( x = 10–48). − Notably, these ion-containing multiblock copolymers microphase separate into ordered morphologies such as lamellar, gyroid, and hexagonally packed cylinder morphologies, and the smallest domain spacing is ∼2.2 nm in the lamellar and hexagonal morphologies of PES10Na. These results suggest that the nonpolar polyethylene blocks are highly incompatible with the polar ionic blocks, indicating a high χ in these PES x Na polymers.…”

Ion transport in small-molecule and polymer electrolytes

“…In a series of studies, Winey and co-workers created polyethylenes containing acid groups that are placed at precisely periodic intervals. 164,165,[213][214][215][216][217] As schematically illustrated in Fig. 10(c), these polymers formed a highly ordered layered structure consisting of crystalline polyethylene domains folded at the acid functional groups.…”

Improved conductivity of single-component, ion-condensed smectic liquid crystalline electrolytes

“…[8][9][10][11][12][13] The rate of the fast ion hopping is significantly higher than the structural relaxation rate of the polymer, leading to a conductivity decoupled from mechanical properties. [14][15][16][17][18][19] The realization of the fast hopping is interesting because of its potential to combine the advantages of both ceramic and polymer electrolytes. 20 Yet, the morphological control of the ionic phase to afford long-range percolation have been difficult to achieve, inhibiting the fundamental experimental study of this kind of novel polymer electrolyte.…”