Quantum-chemical simulation of interaction of polycaproamide with a lithium chloride solution in dimethylacetamide

Quantum-chemical calculations of interaction between lithium chloride and dimethylacetamide (DMAc) and between the polycaproamide model fragment CH₃NHCO(CH₂)₅NHCOCH₃ and a lithium chloride solution in DMAc were performed. The software package GAMESS with the MINI basis set was used in the calculations. Models of the solution included 2 LiCl molecules and 8–16 DMAc molecules. All of these models suggest three potential energy minimums corresponding to three stable structures that differ in the relative arrangement of lithium and chloride ions. A decrease in the amount of solvent in the system leads to transition from Li⁺(DMAc)₄Cl^- to Li⁺...Cl^-(DMAc)₃ and then to the (LiCl)₂(DMAc)₂ species, which crystallizes to form the 1: 1 crystal solvate. The mechanism of dissolution of polycaproamide in DMAc containing lithium chloride was refined.