Balancing hydrophilic vs. hydrophobic volumes: a new approach to enhancing the ionic conductivity of amphiphilic cyclodextrins

Abstract

We report the synthesis, mesophase characterization, and ionic conductivity of a new family of liquid crystalline materials based on amphiphilic β-cyclodextrin (β-CD) derivatives. These unique derivatives are based on a novel design to have 14 aliphatic chains of varying lengths attached to the secondary face of β-CD via ester linkages, and 14 O-monomethyl triethylene glycol units grafted onto the primary face via copper(I)-mediated azide–alkyne cycloaddition (CuAAC) with the help of chlorohydrin chemistry. Compared to previously reported analogues, these amphiphilic CDs exhibit a distinct molecular geometry with an expanded hydrophilic domain. Mesophase studies reveal that derivatives bearing longer aliphatic chains (≥C10) self-assemble into thermotropic liquid crystalline phases, predominantly forming smectic A (SmA) mesophases through nanophase segregation of polar and non-polar regions, while one derivative also demonstrates the ability to form a bicontinuous cubic phase that coexists with the lamellar phase. Solid-state nuclear magnetic resonance (NMR) and variable-temperature X-ray diffraction (XRD) studies confirm the presence of long-range molecular order within the SmA phases. Moreover, impedance spectroscopy reveals that these materials exhibit excellent lithium-ion conductivity, achieving a maximum of 4.86 × 10⁻³ S cm⁻¹, suggesting their potential as a group of promising electrolytes based biodegradable scaffolds. This work underscores the potential of applying innovative molecular designs to enhance the performance of organic electrolytes.