Nonadditive Charge Transport in Bacterial Cellulose/Titanate Nanotube Composites under Controlled Dehydration Probed by Rapid Temperature Cycling

Soft hydrated materials exhibit water-modulated electrical properties, typically studied using time-consuming humidity-controlled methods. Here, rapid temperature cycling is used to probe charge transport in bacterial cellulose (BC), titanate nanotubes (TNT), and their composite (BC/TNT, ∼10 wt % TNT) by impedance spectroscopy. A 35–75–35–75–35 °C cycle (80 min) reproducibly generates water-rich and water-poor states within a single specimen. Under water-rich conditions, the composite shows approximately additive conductivity. Upon dehydration, however, its conductivity decreases and becomes comparable to BC, exhibiting an apparent positive temperature coefficient of resistivity (PTCR) behavior driven by water loss. The relaxation time also increases markedly (∼5.2 to ∼31.8 μs). Consistently, grain resistance of the water-poor composite exceeds that of water-poor BC, further confirming nonadditive transport behavior. This suggests a transition from water-mediated to constrained transport pathways. Atomic force microscopy reveals spatially heterogeneous conduction, while variable-temperature X-ray diffraction confirms structural stability of the cellulose matrix. It is deduced that the observed changes in transport properties arise from hydration-dependent interactions rather than structural transformation. Thermogravimetric analysis further supports modified water–cellulose interactions as evidenced by a shift of the water-loss peak to higher temperature in BC/TNT. Impedance spectroscopy under rapid temperature cycling thus provides an efficient approach to probe hydration-controlled transport mechanisms in soft materials.