Construction of higher-ordered structures in alkylpyridinium-based polymers via π-conjugated anion pairing and humidity Annealing

Abstract

In this study, π-conjugated anions were used as counterions in poly(4-vinyl-N-alkylpyridinium) (P4VC x P⁺) to construct highly ordered ionic microstructures. Nuclear magnetic resonance, Fourier transform infrared, and ultraviolet-visible spectroscopies, and differential scanning calorimetry were employed to characterize the resulting ion-pair polymers.Furthermore, thin films were fabricated and subjected to humidity annealing above the glass transition temperature.Grazing-incidence small-angle X-ray scattering showed that humidity annealing promoted the formation of hexagonally packed cylindrical microdomains in P4VC x P⁺ with π-conjugated anions. The π-conjugated anions increased the effective hydrophilic volume and facilitated the structural alignment via π-π and dipole-dipole interactions. Optical absorption analysis indicated that both pyridinium and π-conjugated anions exhibited end-on orientations and revealed the dynamic behavior of 7,7,8,8-tetracyanoquinodimethane radical anion, including dimerization and charge-transfer complex formation. Thus, π-conjugated ion pairs show significant promise for the controlled self-assembly and functional optical properties of polymeric materials.