Laser-Defined States and Hydration-Driven Relaxation in PEDOT:PSS.

Conductive polymers such as PEDOT:PSS undergo complex structural and electronic changes under external stimuli, yet their state evolution under sequential thermal and hydration processes remains poorly understood. Here, we investigate laser-water interactions in PEDOT:PSS from the perspective of material state evolution and relaxation rather than simple modification and erasure. Using a mechanically interlocked PEDOT:PSS configuration that remains stable under repeated laser irradiation and hydration, we systematically examine how laser-defined material states evolve upon subsequent water exposure. Continuous-wave laser irradiation induces a distinct non-carbonized blue optical transition that is clearly distinguishable from irreversible carbonization. Upon water exposure, this laser-defined state exhibits reversible optical and morphological changes, while the extent of relaxation strongly depends on the prior laser irradiation conditions. Correlative analyses of surface and internal morphology, molecular structure, and electrical response reveal that hydration-driven relaxation does not necessarily restore the pristine state but instead proceeds along pathways determined by the laser-induced configuration. These findings demonstrate that water acts as an active mediator of state relaxation rather than a simple reset mechanism. This work provides a framework for understanding history-dependent state evolution in hydration-sensitive conductive polymers under sequential laser and environmental stimuli.