Investigation of structure and properties of polymerizable deep eutectic solvent based on choline chloride and acrylic acid

Deep eutectic solvents (DESs) are multi-component solvents appearing in a broad range of applications. The next necessary step for the development of new DESs is understanding the molecular mechanisms of DES formation and the interactions that determine its structure and properties. In this work, we use multiscale simulations supported by experiments to investigate the detailed structure and properties of polymerizable DESs based on choline chloride and acrylic acid as a basis for creating inks for 3D printing. Thermodynamic and structural analyses show the physical mechanisms of DES formation in these materials: due to the significant size difference between the acrylic acid and choline ions, and favorable interactions between acrylic acid and the Cl- ions, the acrylic acid molecules are able to incorporate into the free spaces of the first coordination shells of the Cl- ions. As a consequence, the mixture has less volume than its individual components and this excess volume determines the negative value of the enthalpy of mixing. Structurally, the mixture is a network with the Cl- ions as nodes connecting the other DES components. This was confirmed by both the FTIR experiments and the atomistic MD simulations. The calculations show the necessity of correct accounting of excess enthalpy and entropy for determining DESs structures and other properties.