Theoretical evaluation to improve the performance of composite wax powder: cooperativity effects involving the strong Na+•••π/σ and weak hydrogen-bonding interactions in the complex of graphene oxide with Na+ and CH4

To provide a reasonable design scheme to improve the performance of composite wax powder, the ternary complex Na+center dot center dot center dot graphene oxide (GO)center dot center dot center dot CH4 was selected as a model system to evaluate the cooperativity effect between the Na+center dot center dot center dot sigma/pi and H-bonding interactions in the composite wax powder doped with GO at the M06-2X/6-311++G(2d,p) and MP2/6-311++G(2d,p) levels. The cooperativities in GO center dot center dot center dot(CH4)(n) (n = 1 similar to 10) and thermodynamic cooperativity effects in Na+center dot center dot center dot GO center dot center dot center dot CH4 were also investigated. Although the changes of the absolute values of H-bonding interactions were slight, from those of relative values, the influence of the Na+center dot center dot center dot pi or Na+center dot center dot center dot O interaction on the C-H center dot center dot center dot pi, O-H center dot center dot center dot C or C-H center dot center dot center dot O interaction was notable upon the formation of ternary systems. The anti-cooperativity effect was found in the cyclic structure, while the cooperativity effect appeared in the linear conformation. The Na+center dot center dot center dot sigma/pi and H-bonding interactions as well as cooperativities in Na+center dot center dot center dot GO center dot center dot center dot CH4 were stronger than those in Na+center dot center dot center dot coronene center dot center dot center dot CH4. The formation of Na+center dot center dot center dot GO center dot center dot center dot CH4 is a thermodynamic cooperativity process driven by the enthalpy change. Therefore, it could be inferred that, when graphite powder or carbon black was replaced by GO, the compatibilities could be strengthened among various components, and thus the performance of casting moulds could be improved. Atoms-in-molecules (AIM) and reduced density gradient (RDG) analyses confirmed the cooperativity effect and revealed the nature of the improved performance of composite wax powder with GO. The GO center dot center dot center dot(CH4)(n) (n = 1 similar to 3) are positively cooperative, while the negative cooperativity is shown when n = 4 similar to 10. [GRAPHICS] .