Preparation of carbon-containing, compressible, microporous, polymeric monoliths that regulate macroscopic conductivity†
Porous polymer monoliths are of great importance as a multi-scale material in the fields of materials science and chemical engineering. Herein, we create compressible, microporous, composite monoliths that are capable of regulating macroscopic conductivity in response to external compressive force. The materials have been synthesized via a bottom-up approach and behave as sponge materials. The monolithic polymer networks could be prepared using various monomeric building blocks and further incorporated with carbon additives during condensation polymerization. Accordingly, physical properties, such as morphology, mechanical strength, and miscibility, were investigated. Taking advantage of microporosity of these frameworks, the carbon-containing composites were found to be fairly lightweight yet substantial, and non-conductive despite the presence of 10 wt% conductive carbon additives. However, the intrinsic compressibility of the networks significantly altered the resistivity of materials (e.g., ρ < 102 Ω m) when the density of the materials increased following the application of an external force, which is comparable to doped silicon or other clays. As a proof of concept, we used the composite material as a switch for an electrical circuit. Therefore, we were able to repeatedly turn on and off a light-emitting diode in the circuit by hand.