The discovery of reversible-deactivation radical polymerization (RDRP) has provided an avenue for the synthesis of a vast array of polymers with a rich variety of functionality and architecture. The preparation of block copolymers has received significant focus in this burgeoning research field, due to their diverse properties and potential in a wide range of research environments. This tutorial review will address the important concepts behind the design and synthesis of block copolymers using reversible addition-fragmentation chain transfer (RAFT) polymerization. RAFT polymerization is arguably the most versatile of the RDRP methods due to its compatibility with a wide range of functional monomers and reaction media along with its relative ease of use. With an ever increasing array of researchers that possess a variety of backgrounds now turning to RDRP, and RAFT in particular, to prepare their required polymeric materials, it is pertinent to discuss the important points which enable the preparation of high purity functional block copolymers with targeted molar mass and narrow molar mass distribution using RAFT polymerization. The key principles of appropriate RAFT agent selection, the order of monomer addition in block synthesis and potential issues with maintaining high end-group fidelity are addressed. Additionally, techniques which allow block copolymers to be accessed using a combination of RAFT polymerization and complementary techniques are touched upon.

Chain polymerizations are defined as chain reactions where the propagation steps occur by reaction between monomer(s) and active site(s) on the polymer chains with regeneration of the active site(s) at each step. Many forms of chain polymerization can be distinguished according to the mechanism of the propagation step (e.g., cyclopolymerization – when rings are formed, condensative chain polymerization – when propagation is a condensation reaction, group-transfer polymerization, polyinsertion, ring-opening polymerization – when rings are opened), whether they involve a termination step or not (e.g., living polymerization – when termination is absent, reversible-deactivation polymerization), whether a transfer step is involved (e.g., degenerative-transfer polymerization), and the type of chain carrier or active site (e.g., radical, ion, electrophile, nucleophile, coordination complex). The objective of this document is to provide a language for describing chain polymerizations that is both readily understandable and self-consistent, and which covers recent developments in this rapidly evolving field.

The scope for synthesis of new macro-RAFT agents (Z–C(S)S–(M)–R) by sequential insertion of monomers (M) ‘one at a time’ into an initial RAFT agent (Z–C(S)S–R) has been explored. The process is illustrated with the preparation of a styrene-N-isopropylacrylamide (NIPAM) co-dimer macro-RAFT agent [(CH₃)₃C(CN)–CH₂CH(Ph)–CH₂CH(CONHiPr)–SC(S)–S-alkyl] by successive single unit monomer insertions into a cyanoisopropyl trithiocarbonate. Critical factors for success are a high transfer constant for the RAFT agent and a high rate of addition of the radical (R·) to monomer relative to further propagation. With these conditions satisfied, the rate of reaction is largely determined by the rate of R· adding to monomer. Initiator-derived by-products (Z–C(S)S–(M)–I) become an issue when R· is different from the initiator-derived radical (I·).