The development of green and sustainable approaches for producing polymeric materials with targeted properties and functions, as well as for depolymerizing synthetic polymers, is highly desired. In this context, N-isopropylmethacrylamide (NIPMA)-based natural deep eutectic monomer (NADEM) systems, which correspond to NADEM solutions and monomeric deep eutectics, have been developed as promising functional motifs owing to the versatility of their chemical structures and feed ratios of solid NIPMA and solid natural compounds (e.g., oxalic acid, thymol, and menthol) that interact with each other. This versatility enables the manipulation of the properties of NADEM solutions and the resulting polymers. The choice of natural compounds was found to affect the feasibility of forming liquid NADEM solutions with varying viscosities via a strong eutectic effect, as well as subsequent polymerization, by tuning the reactivity of the vinyl group in NIPMA through specific interactions with these compounds. NIPMA-based NADEM solutions are versatile for green free-radical and RAFT polymerizations, producing high-molecular-weight (Mw > 1,000,000) and well-defined (Mn = 3600–12,900, Mw/Mn = 1.14–1.31) PNIPMAs under thermally induced condition. Photo-RAFT polymerization of NIPMA-based NADEM solutions proceeded in a reasonably controlled manner, depending on the nature of the natural compounds. A natural deep eutectic solvent (NADES) was also demonstrated to be effective in the depolymerization of RAFT-synthesized PNIPMA. The discovery of an efficient synthesis of semi-natural polymers from NADEM solutions and the validity of NADES for depolymerization can contribute to the development of comprehensive green radical polymerization/depolymerization systems assisted by natural deep eutectics (NADEM/NADES), leading to the sustainable growth of the chemical industry in the future.
Yoshimura et al. (Wed,) studied this question.