RAFT Reagents

About 15 years ago, a team from the Australian Commonwealth Scientific and Research Organization (CSIRO) discovered the RAFT (Reversible Addition-Fragmentation chain Transfer) polymerization method, which was published in Macromolecules 31(16):5559-5562. This elegant process follows radical-initiated growing polymer chains to degenerative transfer reactivity from one to another using functional groups such as Di thioesters, Tri thiocarbonates, Xanthates and Dithiocarbonates.

RAFT agents minimize uncontrolled growth of propagation and prevent undesirable chain transfer termination events from occurring, effectively controlling the polymer architecture and properties such as molecular weight and polydispersity of end products. The control of microstructure of polymer, such as tacticity, by this process can not be tailored to the best of our literature survey(I don’t understand its meaning). Most RAFT reagents are commercially available, and their viability increases day by day. A key feature of RAFT polymerization is the absence of cytotoxic heavy metal components, unlike Atom Transfer Radical Polymerization (ATRP) process.

Uniqueness OF RAFT

• Compatible with a wide range of functional groups, solvents, and monomers, including aqueous or no solvent environments.

• Simplified purification requirements for solvents or monomers (typically 97-98% purity is acceptable), especially compared to living anionic or cationic polymerizations.

• The ability to tailor RAFT moiety with specific functional group enables the production of polymers with mono- or telechelic quantitative functionality, facilitating further processing.

• RAFT polymerization can often be conducted in standard laboratory equipment, such as round-bottom flask, using common free radical initiators like V70 and AIBN at moderate temperatures (40oC to 90oC).

Drawbacks of RAFT

A. Strong odor of RAFT agents (in the presence of thiol) during using

B. Occasional formation of side products that can be challenging to remove at ppb scale as required by industries such as electronic and pharmaceuticals.

Classification of RAFT

A. RAFT Xanthates Group: Z typically represents an alkyl (e.g., ethyl) moiety.

B. RAFT Dithioesters Group: Z typically represents a phenyl moiety.

C. RAFT Trithiocarbonates Group : Z typically represents a longer alkyl chain(e.g., C12H25).

D. RAFT Dithiocarbamates GROUP: Z1 is typically methyl and Z2 represents alkyl moiety.