Improvements in properties of polybenzoxazine-based laser-induced graphene (LIG) by alloying with polyimide and modeling of production process

Abstract

Laser-induced graphene (LIG) is conventionally produced from polyimide among thermosetting polymer substrates, but its flexible nature limits its tremendous potential in applications where flexibility of the substrate is not desired. Interestingly, polybenzoxazine has also been found to have potential as a substrate in LIG production. However, aside from being brittle, it has inferior char residue and thermal stability relative to polyimide, which could result in the production of LIG with inferior properties. Thus, exploring possible improvements in the properties of the polybenzoxazine-based substrate and LIG by alloying with polybenzoxazine and polyimide is the major motivation of this study. First, the improvement in the toughness, char residue and thermal stability of polybenzoxazine by alloying with polyimide was explored. Second, the properties of a LIG obtained from the polybenzoxazine/polyimide alloy were studied. The electrical sheet resistivity, Raman spectra indices, structural morphologies, and crystal size of the neat polybenzoxazine and polybenzoxazine/polyimide alloy substrates were compared. The results reveal significant improvements in the electrical resistivity, structural morphology, and crystal size of the LIG. In addition, the improved polybenzoxazine/polyimide alloy substrate was used to optimize the operational parameters of the laser machine for the production of the LIG. LIG with a minimum electrical sheet resistivity of 3.61 Ω sq⁻¹, multi-layer crystals as confirmed by Raman spectroscopic analysis, and a sponge-like highly porous structure was achieved with the optimum operational conditions in an ambient environment. Last, a quadratic model was found and validated to suitably define the production process. The study demonstrated an improvement in the property of a rigid polybenzoxazine-based LIG by alloying polybenzoxazine with polyimide for the first time.