EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Oxidative chemical vapor deposition (oCVD) is a solvent-free technique, enabling growth of network polymers with stoichiometric compositions in a single processing step. Deposition proceeds via vapor-phase eliminating limitations of insufficient monomer solubilities of conjugated polymers (CPs) faced by conventional methods. Further, unlike traditional methods, oCVD accommodates mild operation conditions providing additional advantages such as the ability to conformally coat sensitive substrates or 3D porous microstructures. In this work, we use oCVD to engineer hybrid conductive polymer hydrogels (CPHs). CPHs are excellent candidates for a plethora of biomedical applications that rely on electrical conductivity, including wearable and flexible resistive strain sensors for healthcare monitoring.

We have developed hybrid CPHs which combine strong mechanical and electrical properties. Ultrathin hydrogel films with gradient microstructure and tunable porosity have been synthesized using two different techniques: (1) salinity-triggered phase-separation of polyelectrolyte complexes, and, (2) electrospinning. Porous interconnected hydrogels serve as a molecular template, guiding in-situ vapor-phase polymerization of a CP backbone into the matrix by oCVD. The growth mechanism of oCVD CP network alongside physicochemical properties of CPHs have been investigated. CPHs are synthesized by oCVD of polypyrrole (PPy) on free-standing hydrogels. FTIR spectroscopy confirms formation of PPy and SEM imaging shows conformal coating of oCVD PPy on the pore-walls within the microstructure. Current work includes mapping dispersion of PPy network inside the hydrogel matrix. Effect of different parameters such as reactant flowrate, substrate temperature, and pressure on the growth rate will be presented. A good control over the deposition parameters enable tunable mechanical and electrical properties of the resulting material. Synergistic interpenetrating CP chains throughout the hydrogel matrix can be used to reversibly manipulate mechanical and electrical properties of the designed CPH.