Advances in Switchable RAFT Polymerization

Abstract

Summary: This paper reviews recent developments in RAFT Polymerization with proton switchable RAFT agents. We report on the successful use of N-methyl-N-(4-pyridinyl) dithiocarbamates RAFT agents for controlling the polymerization of N, N-dimethylacrylamide (DMAm) in aqueous media, the dependence of the RAFT agent activity on acid type and acid strength (for best results a stoichiometric amount of a strong acid should be used), and the synthesis of block copolymers such as poly(DMAm)-block-poly(N-vinylpyrrolidone). We describe a new class of switchable RAFT agents, the N-aryl-N-(4-pyridinyl) dithiocarbamates. These RAFT agents are more active with more activated monomers (MAMs) in protonated (switched) form and more active with less activated monomers (LAMS) in non-protonated (unswitched) form. Finally we examine the dependence of RAFT polymerization of N-vinylcarbazole (NVC) on the type of RAFT agent used (dithiobenzoate, trithiocarbonate, xanthate, switchable dithiocarbamate). Contrary to popular belief, NVC does not behave as a typical LAM, its polymerization is best controlled with a trithiocarbonate RAFT agent, and NVC should be described as an intermediate activity monomer (IAM).

Poly(styrene/pentafluorostyrene)‐block‐poly(vinyl alcohol/vinylpyrrolidone) amphiphilic block copolymers for kinetic gas hydrate inhibitors: Synthesis, micellization behavior, and methane hydrate kinetic inhibition

“…This initiator to RAFT agent concentration ratio has been proposed as a method to obtain narrower molecular weight distributions. A larger than usual ratio has shown to decrease Ð down to 1.1–1.3 . Initiator to RAFT agent ratio of 1:20 and 1:15 were first used; however, those polymers obtained had higher dispersities.…”

RAFT Polymerization – Then and Now

“…Developments in this area have now been reviewed (69). In more recent work, we demonstrated the effectiveness of switchable RAFT in aqueous media (53), and explored the use of N-aryl-N-(4-pyridinyl)dithiocarbamates (52).…”

“…General reviews include those by Moad, Rizzardo and Thang (14,15,(62)(63)(64)(65) Destarac (66), and Barner-Kowollik et al (67). Reviews devoted to RAFT or RAFT polymerization in specific areas include those on the origins of RAFT polymerization (3), the design and synthesis of RAFT agents (48), advances in Switchable RAFT agents (68,69), dithiobenzoate-mediated RAFT polymerization (70), RAFT chemistry using xanthates (4,71), RAFT polymerization of vinyl esters (72), RAFT crosslinking polymerization (73), RAFT polymerization in microemulsion (74), RAFT polymerization induced self-assembly (75,76), the synthesis of block copolymers (77), the synthesis of star polymers and other complex architectures (78)(79)(80)(81), block copolymers based on amino acid-derived monomers (82), end group removal and transformation (83)(84)(85)(86), the synergistic use of RAFT polymerization and ATRP (87), microwave-assisted RAFT polymerization (88,89), silica nanoparticles (90), polymer nanocomposites (91,92), the use of RAFT-synthesized polymers in gene-delivery (93), drug delivery and bioapplications (79,(94)(95)(96)(97)…”

Polymer Synthesis with More Than One Form of Living Polymerization Method

“…Further efforts should be focused on the simplification of transformation reactions and the screening of the hetero‐functional initiators. For example, Thang and coworkers had described the use of pH “switchable” RAFT agents in a convenient synthesis of poly(MAMs)‐ block ‐poly(LAMs) with narrow molecular weight distributions . It allows a wide combinations of monomers to polymerize according to one universal mechanism, leading to a broad spectrum of novel block copolymers.…”