RAFT without an “R-Group”: From Asymmetric Homo-telechelics to Multiblock Step-Growth and Cyclic Block Copolymers

Abstract

The amalgamation of photoredox catalysis and reversible-deactivation radical polymerization (RDRP) has offered new avenues of controlling polymer synthesis in recent years. Additionally, the incorporation of bismuth oxide catalysts offers advantages to overcome the limitations of current endogenous catalysis. In this study, we used bismuth oxide to employ dithiocarbonyl disulfides as chain transfer agents (CTAs) in reversible addition−fragmentation chain transfer (RAFT) polymerizations. Despite using CTA precursors with a symmetric molecular structure, we show that the corresponding homotelechelic (co)polymers propagate with asymmetric growth in one direction only. We employed this methodology to produce homotelechelic AB diblock copolymers and ABC triblock terpolymers, which after aminolysis can undergo reversible oxidative step-growth polymerization or ring-closure to form either unusual multiblock copolymers or cyclic block copolymers.

Photoiniferter-RAFT polymerization mediated by bis(trithiocarbonate) disulfides

“…However, the polymerization only proceeded in the presence of the photoredox catalyst – bismuth oxide. 44 Bis(thiocarbonyl) disulfides were also used as chain transfer agents in organo-catalysed photocontrolled radical polymerization with sulfonyl chlorides as initiators. 45 The potential of disulfides as agents capable of both initiating and reversibly deactivating polymer chain growth has been recognised as early as the late 1950s by Otsu and co-workers both in photo- and thermal-iniferter systems.…”

Light-Driven Organocatalyzed Controlled Radical Polymerization from Sulfonyl Chloride Initiators Promoted by Bis(thiocarbonyl) Disulfides

“…Beyond CRPs from ArSO 2 Cl, disulfides were seminally employed by Otsu as photo-iniferters since 1982, , which have gained considerable interest afterward. , Recently, the adoption of bis­(trithiocarbonate) disulfides has promoted investigations toward photo-CRP based on C–H bond functionalization, piezoelectrically mediated RAFT polymerization, regulation of polymer sequence and topology, as well as convergence of ATRP and RAFT polymerization under thermal or photo conditions. , Motivated by the well-demonstrated RAFT equilibrium with bis­(trithiocarbonate) disulfides, we envisioned that the incorporation of such disulfides as chain transfer agents (CTAs) could promote chain growth control for the photoredox-mediated polymerization from ArSO 2 Cl initiators.…”

Cascade synthesis of architecture-transformable thermo-labile multisite multiblock copolymers

“…In general, MMBPs and their derivatives can be synthesized by some strategies such as chain polymerization [44][45][46][47][48][49][50] and stepwise polymerization/linking reaction. [51][52][53][54][55][56][57][58][59][60][61][62][63][64] Chain polymerization via "living"/controlled procedures allows to synthesize well-defined MMBPs with controlled block order and relatively low dispersity, while other methods using presynthesized telechelic polymers or reactive precursors usually afford MMBPs with predetermined block order and relatively high dispersity. MMBPs can be potentially synthesized by either multi-step or one-pot 24,31,33,[59][60][61][62][63][64] route.…”

“…40–43 As reactive linkers and side groups are incorporated into multiblock copolymers, the resultant multisite multiblock copolymers (MMBPs) may exhibit more flexible topological transformations among linear, cyclic, branched and single-chain folding architectures. 44–64 In general, MMBPs and their derivatives can be synthesized by some strategies such as chain polymerization 44–50 and stepwise polymerization/linking reaction. 51–64 Chain polymerization via “living”/controlled procedures allows to synthesize well-defined MMBPs with controlled block order and relatively low dispersity, while other methods using presynthesized telechelic polymers or reactive precursors usually afford MMBPs with predetermined block order and relatively high dispersity.…”