Reactive molecular dynamics simulations of the surface interactions between atomic oxygen and poly(2,5)benzimidazole carbon nanotube composite

Abstract

The low Earth orbit (LEO) environment is home to many species, of which atomic oxygen (AO )is the most abundant. AO is formed via the photo-disassociation of molecular oxygen by solar radiation. In the LEO environment, AO collides with space craft material and causes the degradation of the material. Organic materials such as polymers used in space applications are most susceptible to the degradation caused by AO. In this investigation, computational modelling in the form of reactive molecular dynamics (MD) is employed to simulate the interaction between AO and polymer materials and their composite variations. There active MD simulations were performed using the reactive force field ReaxFF, which can perform MD simulations of sufficiently large systems within the realm of MD while including the chemistry of the reactions at a somewhat low computational runtime. Using these simulations, the polymer poly(2,5)-benzimidazole (ABPBI) and carbon nanotube (CNT) loaded variations were exposed to AO bombardment to test both the efficacy of pristine ABPBI and the effects of adding CNT against degradation caused by AO bombardment. The simulations in this study indicate that ABPBI and CNT composite variations show high stability against AO bombardment. A second study considered the effects of low temperature in combination with AO bombardment. The outcome of this study shows a decrease in degradation caused by AO bombardment when combined with a decreased simulation temperature for the pristine ABPBI system. The conclusions of this work have given insight into the extent of degradation to ABPBI because of AO bombardment. The favourable results of adding CNTs to the polymer matrix indicate that its addition can further enhance the materials' properties and shows promise for space applications.