liquidassisted

Liquid-assisted refers to processes in which a small amount of liquid is introduced to a system to facilitate a chemical or physical transformation, without forming a homogeneous solution with the reactants. The approach is contrasted with neat (dry) methods and with fully solvated, liquid-phase reactions. The term is commonly used in solid-state chemistry and materials science, where limited solvent access can markedly influence outcomes.

In practice, a liquid is added in minimal quantities to solid reactants or precursors. The liquid can act as a lubricant to improve particle contact, as a medium that enhances diffusion at interfaces, or as a localized solvent that stabilizes reactive species and transition states. The outcome depends on solvent identity, volume, and the physical properties of the system, such as polarity and viscosity. Because only traces of liquid are used, the method often preserves characteristics of solid-state reactions while enabling pathways that would be inaccessible under strictly dry conditions.

Liquid-assisted methods are widely applied in areas such as mechanochemistry, where liquid-assisted grinding (LAG) enables synthesis and crystallization of otherwise difficult solids; crystal engineering and pharmaceutical cocrystallization; and materials synthesis for batteries and catalysis. They are valued for reducing overall solvent use and enabling new polymorphs, phases, or product selectivities. Challenges include selecting appropriate liquids to avoid unwanted contamination or phase changes, and ensuring reproducibility and scalability for larger-scale applications.

See also: mechanochemistry, solvent-assisted grinding, solid-state synthesis, crystal engineering.