Correlation of polymer-like solution behaviors with electrospun fiber formation of hydroxypropyl-β-cyclodextrin and the adsorption study on the fiber

Abstract

In this paper, the formation of hydroxypropyl-β-cyclodextrin (HPCD) nanofibers in electrospinning and the adsorption of organic molecules on the HPCD nanofiber were studied. The properties of a polymer-like solution from the highly concentrated HPCD/N,N-dimethylformamide (DMF) solution revealed HPCD supramolecular aggregates formation. The entanglements of HPCD self-organized aggregates were one of the most important factors that significantly influenced fiber formation during cyclodextrin electrospinning. The HPCD self-organized aggregates entanglement concentration (C_e) was investigated. Analyzing the dependence of specific viscosity (η_sp) on concentration enabled the determination of the aggregates unentangled and entangled regimes for HPCD polymer-like solutions. The dynamic light scattering (DLS) measurements and the ¹H NMR spectra of the HPCD solutions confirmed the presence of considerable HPCD self-organized aggregates in high concentrated HPCD/DMF solutions due to the intermolecular hydrogen bonding. The scanning electron microscopy (SEM) showed the electrospinning morphology transitioned from regular beads to uniform fibers with increasing the HPCD concentration. The dependence of the fiber diameter on the zero shear rate viscosity (η₀) was determined. The static adsorption behavior of the HPCD fibers was studied. Neutral red (NR) was used as a model organic molecule. The adsorption of NR onto HPCD fibers fitted the pseudo-second-order kinetic model. The equilibrium adsorption amount of NR was 18.41 mg g⁻¹, and the apparent adsorption rate constant was 9.83 × 10⁻⁴ g mg⁻¹ min⁻¹ at 25 °C.