Rheo-SAXS study on electrically responsive hydrogels with shear-induced conductive micellar networks for on-demand drug release

This study presents a novel approach to creating electrically responsive hydrogels utilizing a poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) (PEO 100 –PPO 65 –PEO 100 ) triblock copolymer, functionalized with benzenesulfonate end groups to form sF127. This functionalization allows the incorporation of sF127 into F127 micelles, resulting in tailored micelles designated as F 18 S 2 P when combined with poly(3,4-ethylenedioxythiophene):poly(benzenesulfonate) (PEDOT:PSS). For comparison, a control system using non-functionalized PEDOT:PSS/F127 micelles, designated F 20 S 0 P, was also developed. Using piroxicam as a model hydrophobic drug, we evaluated the hydrogel's drug encapsulation efficiency and electrical responsiveness. The functionalized F 18 S 2 P hydrogel demonstrated superior performance of electrically stimulated drug release, especially when prepared with a blade-coating process. In situ rheological small-angle X-ray scattering (rheo-SAXS) measurements under large amplitude oscillatory shear revealed that functionalization facilitates crystal plane sliding, leading to the formation of a randomly hexagonal close-packed (rHCP) sliding layer structure. This behavior contrasts with the face-centered cubic to rHCP phase transition observed in the unfunctionalized hydrogel. In situ SAXS analysis under applied electric fields (E-SAXS) further confirmed the electroresponsive micellar deformation. By integrating the rheo-SAXS and E-SAXS findings with blade-coating processing insights, we identify a clear structure–function relationship that governs the performance of these hydrogels. The enhanced drug delivery of the functionalized F 18 S 2 P hydrogel is attributed to the electrostatic attraction between the positively charged PEDOT and the negatively charged benzenesulfonate-functionalized micelles. This interaction creates conductive nanonetworks within the hydrogel, significantly improving its ability to release drugs in response to electrical stimulation. This work highlights the potential of electrically responsive hydrogels for precise, localized drug delivery applications.