ReaxFF Simulations of Laser-Induced Graphene (LIG) Formation for Multifunctional Polymer Nanocomposites

Abstract

Irradiation of polymer films by a CO 2 infrared laser under ambient conditions converts the polymer into porous graphene or laser-induced graphene (LIG). Here, we simulate the formation of LIG from five different commercially available polymers using reactive molecular dynamics. We determined that the molecular structure of the parent polymer has a significant effect on the final graphitic structure. CO is liberated during the initial part of the LIG formation process when the polymer is converted into an amorphous structure, while H 2 is evolved steadily as the amorphous structure is converted to an ordered graphitic structure. The LIG structure has out-of-plane undulations and bends due to a significant number of 5-and 7-member carbon rings present throughout the structure. We find that the simulated molecular structure compares well with recent experimental observations from the literature. We also demonstrate that the yield of LIG is higher in inert conditions, compared to environments with oxygen. Polybenzimidazole-derived LIG has the highest surface area and yield among the five polymers examined. These findings provide knowledge of LIG formation mechanisms that can be leveraged for bulk LIG applications such as sensors, electrocatalysts, microfluidics, and targeted heating for welding polymers.

Physical Sensors Based on Laser-Induced Graphene: A Review

“…During the initial 0.2 ns of lasing, an amorphous structure is formed that grows into an ordered graphene structure with 6membered carbon rings ( Fig. 2a) [41]. This is in agreement with the results presented by Lin et al [40], where TEM demonstrated the ordered ring structure of graphene formed on the PI (Fig.…”

“…Both studies have also reported unusual structures containing 5-and 7-member rings, which is a result of steric stresses, the rapid formation and cooling of the graphene and trapping it in a higher energy state ( Fig. 2c, d) [40,41]. LIG formation has been generally confirmed via Raman and X-Ray Diffraction (XRD) analyses.…”

“…The general reaction observed during the LIG creation is summarized in Fig. 1b [41]. Typically, the base polymer is heated through a laser, producing LIG and predominantly CO and H2 gases along with hydrocarbon (CxHyNz) species.…”

“…Considering the most commonly used combination of a CO2 laser and PI, carbonization is reported to commence at 673K, while graphitization occurs upon further heating of the PI to at least 773 K [77]. The gases produced from LIG formation are removed from the system after the course of 1.25 ns [41]. During the initial 0.2 ns of lasing, an amorphous structure is formed that grows into an ordered graphene structure with 6membered carbon rings ( Fig.…”

“…This method combines large-area graphene preparation and patterning with a single fabrication step without the need for expensive cleanroom equipment, wet chemical steps, reducing agents, solvents, subsequent treatments, or other supporting processes. This laser-induced graphene (LIG) has stimulated research in many areas, ranging from fundamental to applied sciences, investigating the laser graphitization process [41][42][43], effects of various lasers [44][45][46], environments [47,48], and lasing parameters [49][50][51], to the development of a large variety of flexible physical and chemical sensors. The latter utilizes LIG as an electrochemical transducer while incorporating additional chemical recognition systems and surface functionalization to interact with analytic molecules [52][53][54], such as glucose [55], tyrosine [56], dopamine [57], bisphenol [53], thrombin [58], ascorbic and uric acid [56].…”