Multifunctional PNIPAM Hydrogels Based on Supercritical CO₂-Assisted PEDOT:PSS/SWCNT Hybrid Structure

We report herein the typical conductive polymer poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) to be successfully modified onto single-walled carbon nanotubes (SWCNTs) using a supercritical carbon dioxide (SC CO₂) antisolvent-induced polymer epitaxy method, and the role of the experimental temperature of SC CO₂ on the modification process was systematically investigated. PEDOT:PSS/SWCNTs composites with optimal modification prepared at 80 °C and 15 MPa were used as functional fillers, and functional temperature-sensitive composite hydrogels of PEDOT:PSS/SWCNTs/poly-N-isopropylacrylamide (PNIPAM) were successfully prepared. With the help of Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction, transmission electron microscopy (TEM), scanning electron microscopy (SEM), and other characterization means, the chemical composition and microscopic morphology of the composite hydrogel were systematically analyzed. The composite hydrogel exhibits reversible temperature-sensitive responsiveness, transitioning from a transparent swollen state at room temperature to an opaque collapsed state at 32 °C, and demonstrates strong adhesion to various substrates, including glass, plastic, metal, and skin. Meanwhile, the near-infrared (NIR) photothermal conversion properties of this hydrogel were evaluated, showing a significant and uniform temperature increase upon NIR irradiation. The drug release behavior was assessed in vitro after loading the hydrophilic anticancer drug 5-fluorouracil (5-FU) with the stimulation of NIR light, achieving an accelerated and on-demand release. Our experimental results indicate that the pore size increases with the increase of the addition of PEDOT:PSS/SWCNTs, enabling the precise controlled release of 5-FU. This work provides new insights and experimental support for the design of intelligent drug delivery systems.