The properties and some key applications of solvents such as (1) supercritical fluids (SCFs), (2) gas-expanded liquids (GXLs) and organic-aqueous tunable solvents (OATS), (3) water at elevated temperature (WET), and (4) switchable solvents like reversible ionic liquids (RevILs) are discussed in this review. Each system offers a unique set of properties to enable alternative strategies for varied applications. These applications range from chemical transformations, product separation, catalyst recycling, nanomaterial processing, and CO₂ capture. For each application, however, the common thrust is to enable greener and sustainable solutions for chemical processes.

Dispersions of multiwalled carbon nanotubes (MWNT) in unsaturated polyester resin (UPR) were studied by rheology and optical microscopy. The experimentally determined percolation threshold of 0.097 vol % was very close to the theoretical value of 0.085 vol % expected for individually dispersed MWNT with an average aspect ratio of 590. Rheological analysis showed that the dispersions formed an open network with a fractal dimension of 1.28. The results were compared with single-walled carbon nanotubes (SWNT) and polystyrene (PS)-modified MWNT (MWNT-PS). The SWNT formed stronger networks than MWNT, but the MWNT-PS networks were weaker than unmodified MWNT.