Complex Macromolecular Architectures by Reversible Addition Fragmentation Chain Transfer Chemistry: Theory and Practice

Abstract

Reversible addition–fragmentation chain transfer (RAFT) chemistry can be effectively employed to construct macromolecular architectures of varying topologies. The present article explores the principle design routes to star, block, and comb polymers in the context of theoretical design criteria for the so‐called Z‐ and R‐group approaches. The specific advantages and disadvantages of each approach are underpinned by selected examples generated in the CAMD laboratories. In particular, we demonstrate how the modeling of full molecular weight distributions can be employed to guide the synthetic effort. We further explore the theory and practice of generating amphiphilic block copolymer structures and their self‐assembly. In addition, the article foreshadows how modern synthetic techniques that combine RAFT chemistry with highly orthogonal click chemistry can be employed as a powerful tool that furthers the enhancement of macromolecular design possibilities to generate block (star) copolymers of monomers with extremely disparate reactivities. Finally, the ability of RAFT chemistry to modify the surface of well‐defined nano‐ and microspheres as devices in biomedical application is detailed.magnified image

Living Radical Polymerization by the RAFT Process - A Second Update

“…The past 2 years has seen the publication of further general reviews detailing the RAFT process which include works by Moad, Rizzardo, and Thang, [9][10][11][12] a Handbook of RAFT Polymerization, [13] and a highlight article by Barner-Kowollik and Perrier [14] on the future of RAFT. Reviews on specific areas include the kinetics and mechanism of RAFT polymerization, [15][16][17][18] the use of RAFT to probe the kinetics of radical polymerization, [19,20] the use of RAFT in organic synthesis, [21] amphiphilic block copolymer synthesis, [22,23] the synthesis of end functional polymers, [24] the synthesis of star polymers and other complex architectures, [25,26] the use of trithiocarbonate RAFT agents, [27] the use of xanthate RAFT agents (MADIX), [28] polymerization in heterogeneous media, [29][30][31][32] RAFT polymerization initiated with ionizing radiation, [33] polymer synthesis in aqueous solution, [34][35][36][37] surface and particle modification, [38,39] synthesis of self assembling and/or stimuli responsive polymers, [36,40] RAFT-synthesized polymers in drug delivery, [22,41] and other applications of RAFTsynthesized polymers. [30,42,43] The process is also given substantial coverage in most recent reviews that, in part, relate to polymer synthesis, living or controlled polymerization, or novel architectures.…”

Temperature-responsive self-assembly of star block copolymers with poly(ionic liquid) segments

“…Nevertheless, the results of our investigation are in good agreement with the theoretical guidelines, suggesting that well-defined star polymers can be obtained from monomers with high propagation rate coefficients when the R-group approach is used. 38,41 In fact, the R-group approach has been successfully used for the synthesis of welldefined star polymers of vinyl acetate, 37,49 N-vinyl pyrrolidone 50 and N-vinylcarbazole 42 which form relatively unstable (reactive) propagating radical species and have relatively large propagation rate coefficients.…”

“…[36][37][38][39][40][41] Previously, we synthesized poly(Nvinylcarbazole) stars and star block copolymers using the R-group approach in which the leaving groups are linked to the core, and the core is transformed into a radical by fragmentation. 42 In the present study, two R-designed tetrafunctional CTAs, including a xanthatetype tetrafunctional CTA (CTA 1) and a dithiocarbamate-type tetrafunctional CTA (CTA 2), were used for the synthesis of thermoresponsive-ionic star block copolymers, as shown in Scheme 1.…”

RAFT dispersion polymerization in non-polar solvents: facile production of block copolymer spheres, worms and vesicles in n-alkanes

“…[4][5][6][7][8] This approach has enormous potential for the design of bespoke - 30 any further processing steps. For example, RAFT aqueous dispersion polymerization has been utilized to grow a waterinsoluble core-forming block from a water-soluble stabilizer block in order to prepare a range of sterically-stabilized diblock copolymer nanoparticles.…”