(200i) A Reactive Molecular Dynamics Simulation of the Thermal Decomposition in Graphene-Reinforced Polyethylene Oxide

In this work, we have used the Reactive Force Field (ReaxFF) to investigate the thermal decomposition of the virgin and graphene-reinforced polyethylene oxide (PEO). Our objective has been to elucidate the effects of the type and concentration of graphene platelets in the host polymer matrix, as well as the confinement effect of the PEO molecules in the galleries of the graphene platelets, on the kinetics and thermodynamics of the polymer thermal decomposition. We generated six different systems composed of 1) virgin PEO, 2) PEO/graphene with two graphene platelets, 3) PEO/graphene with four graphene platelets, 4) and 5) PEO/graphene oxide (GO) with two and four graphene platelets, respectively, and 6) PEO confined between two graphene platelets. Our first set of NVT simulations were comprised of cook-off simulations from 298 K up to 3,400 K for a total simulation time of 200 ps (a temperature increase rate of 16 K/ps). We used a time step of 0.05 fs for all simulations and controlled the temperature by the Nosé-Hoover thermostat with a damping parameter of 100 fs. We also performed ten independent 20-ps NVT simulations of the virgin PEO and high-concentration PEO/graphene and PEO/GO systems between 2,500-3,400 K with an interval of 100 K. We have quantified and experimentally validated the rate of polymer decomposition as a function of temperature. We have also determined the weight distribution and types of the species formed during the decomposition process. Our initial results show that the onset of PEO decomposition is shifted towards lower temperatures with increasing graphene and GO concentrations. Moreover, in the confined region between the two graphene platelets, the polymer chains decompose into larger species than those formed in the virgin PEO and low-concentration PEO/graphene and PEO/GO systems. For the first time, this study sheds new light on the effect of graphene nanoparticles on the kinetics and thermodynamics of polymer thermal decomposition using a reactive molecular dynamics simulation. Such molecular insight will enable the design of hybrid systems for use in extreme environments.