(524h) Photocrosslinking to Obtain Graphitic Carbon-Based Nanowires from Ordered Polymer Networks

Polyethylene oxide (PEO) has been widely used for electrospun microfibers due to its viscoelastic properties. However, PEO is not a suitable candidate for the production of graphitic nanowires from pyrolysis. In contrast, aromatic epoxy oligomers yield carbon-based materials with a higher content of graphitic carbon after pyrolysis. Here, we analyze the Near Field Electrospinning (NFES) of a mixture of PEO and multi-functional epoxy crosslinkers as a candidate for the production of spatiotemporally fixed polymer fibers that can be converted into conductive carbon-based materials. The fabrication of photopolymerizable micro- and nanofibers from NFES has remained relatively unexplored. Here, we explore the influence of the crosslinking reaction on the properties of the fibers and of the final nanowires. We correlate fiber diameter before and after irradiation to the viscosity, conductivity, and surface tension of the solutions as a function of the PEO loading using dimensional analysis. The cationic photopolymerization kinetics were analyzed to determine curing times and the effect of post-curing treatment. An ideal crosslinker/PEO ratio is proposed, which allows electrospinning at low voltages while ensuring the smallest fiber diameter possible, sub-micrometer range. While the physicochemical properties of SU-8/PEO solutions vary only slightly, the fiber diameter is significantly affected by the SU-8/PEO ratio. The correlation of diameter to PEO-content is based on SEM analysis of the electrospun fibers before and after pyrolysis, and fits well with previous studies of electrospun PEO-based microfibers. We report the first study on the effect of crosslinker/PEO ratio on final diameter for photopolymerizable PEO-based microfibers at the low voltages and short distances used in Near Field Electrospinning (NFES) and Electromechanical Spinning (EMS). These fibers were pyrolyzed to produce graphitic carbon-based micro- and nanowires useful for biosensors.