So-called deep eutectic solvents polyethylene glycol-acetamide are not deep and not eutectic but just solvents via phase diagram

Polyethylene glycol:acetamide (PEG:acetamide) are deemed as one of typical deep eutectic solvents (DESs) with low cost, high biodegradability and easy-synthesizing procedure in previous reports. However, there is no clear evidence validating that PEG:acetamide are DESs. The reliable evidence of DESs is phase-diagram. Here, contrary to the previous reports, we found that PEG:acetamide are not deep and not eutectic but just solvents according to the phase diagram. Acetamide owns melting point while there is no melting point for PEG. It gives us a hint that the widely-used so-called DESs (e.g., polyethylene glycol-acetamide) might not be really deep and eutectic; sometimes, they might be just common solvents.