D. Naranjo et al. Conductive nanocomposites as molecular modulators of hydration in thermoresponsive PNiPAAm-derivative hydrogels. Materials Today Physics

D. Naranjo, S. Lanzalaco, A.H.M. Mohammed-Sadhakathullah, N. Borras, J. García-Torres, J. Torras. Conductive nanocomposites as molecular modulators of hydration in thermoresponsive PNiPAAm-derivative hydrogels. Materials Today Physics 60 (2026) 101998. OPEN ACESS

doi: doi.org/10.1016/j.mtphys.2025.101998

Abstract

Thermoresponsive hydrogels based on poly(N-isopropylacrylamide) (PNiPAAm) and its derivatives are promising for advanced applications, including solar-driven water purification, due to their tunable volume phase transition (VPT) behavior. In this study, we investigate the effect of poly(3,4-ethylenedioxythiophene) (PEDOT) nanoparticles (NPs) on the VPT of three PNiPAAm derivatives: poly(N-n-propylacrylamide) (PNnPAAm), PNiPAAm, and poly(N-isopropylmethacrylamide) (PNiPMAAm), with distinct hydrophobic side chains. Macrohydrogels were synthesized with and without PEDOT, and their thermal responsiveness was characterized using temperature-dependent Raman spectroscopy, which enabled differentiation between intermediate and free water. Incorporation of PEDOT systematically increased swelling ratios and pore sizes, with the most pronounced effects observed below the lower critical solution temperature, and promoted the formation of intermediate water strongly associated with the polymer network. Molecular dynamics simulations corroborated these observations, showing enhanced water–polymer interactions in the presence of PEDOT, while quantum mechanical calculations revealed stabilization of hydrogel–PEDOT complexes through weak polar interactions and increased electronic polarization, which reinforce hydrogen bonding and modulate the local electrostatic environment. These combined experimental and computational results provide a molecular-level understanding of how conductive polymers influence hydration structure and VPT thermodynamics, offering a framework for rationally designing smart hydrogels with tailored swelling, porosity, and water-binding properties for energy-efficient materials applications.