Tailoring pore structure in nanocellulose cryogels: Enhancing thermal and electromagnetic interference shielding properties

Engineering porosity levels in hierarchical cryogels presents an exciting opportunity for advancing electromagnetic interference (EMI) shielding materials. This study introduces a feasible approach to tailoring micro-scale morphology in cellulose nanofiber (CNF)-based cryogels by simply adjusting the freeze-templating temperature, resulting in tunable porosity and enhanced performance characteristics. By varying the freeze-templating temperature, we successfully controlled pore size (ranging from 31 to 178 μm), which influenced the mechanical strength (decreasing from 59 to 14 kPa). To explore the effect of micro-scale porosity on the EMI shielding performance, we rendered the CNF cryogels conductivity upon integrating poly(3,4-ethylenedioxythiophene) (PEDOT) with the cryogels framework via chemical vapor polymerization. Our results demonstrate that the larger pore sizes promoted an absorption-dominant EMI shielding mechanism, with an average absorbance (A) of 0.59 across the X-band frequency range. A specific EMI shielding effectiveness (SSE/t) of 4801.25 dB cm2 g-1 was achieved for samples with larger porosities, highlighting the decent performance of these engineered cryogels. Our findings reveal a straightforward yet effective strategy for optimizing porosity to achieve appreciable shielding effectiveness, contributing to the advancement of sustainable, high-performance EMI shielding solutions.