One‐Pot Synthesis of Block Copolymers by a Combination of Living Cationic and Controlled Radical Polymerization

Abstract

The reversible addition-fragmentation chain-transfer (RAFT) process represents a sophisticated polymerization technique for the preparation of tailored and well-defined polymers from acrylates, acrylamides, and (meth)acrylates. The direct switching from other methods, such as cationic polymerizations, without the need for tedious functionalization and purification steps remains challenging. Within this study, it is demonstrated that poly(2-oxazoline) (P(Ox)) macro chain-transfer agents (macro-CTAs) can be prepared through the quenching of the cationic ring-opening polymerization with a carbonotrithioate salt. The end-functionalization of the P(Ox)s is observed to be almost quantitative and the macro-CTAs could be directly used for RAFT polymerization without further purification. This one-pot procedure could be extended to a variety of (multi)block copolymers consisting of different 2-oxazolines and acrylates with good-to-excellent control. Kinetic studies revealed the controlled polymerization of block copolymers, which are further accessible for α- and ω-end-functionalization. The simplicity and versatility of the approach promise a straightforward access to block copolymers from cationic and controlled radical polymerizations.

Straightforward access to biocompatible poly(2-oxazoline)-coated nanomaterials by polymerization-induced self-assembly

“…30 PEtOx was synthesized by CROP using methyl tosylate as an initiator. As shown in Scheme 1, the CTA end group could be incorporated either by direct capping with a deprotonated carboxylic acid-functionalized CTA (Route A) 31,32 or by a two-step sequence consisting of a nucleophilic substitution with sodium azide and a subsequent copper-catalyzed azide-alkyne cycloaddition (CuAAC) (Route B). Both routes showed similar kinetic features and fulfilled elementary criteria for a controlled/living polymerization, i.e., linear increase of pseudo-first order plot, linear increase of number-average molar mass with conversion, and a clear shift of size-exclusion chromatography (SEC) traces ( Fig.…”

Orthogonal synthesis and modification of polymer materials

“…Schubert and coworkers, in their seminal work, accomplished three objectives at once: performed one‐pot orthogonal ROP and RAFT polymerizations for block copolymerizations, synthesized well‐defined polymers from a variety of functional monomers, and extended this approach to make a complex multiblock copolymer with narrow molecular weight dispersity 85 . Essentially, poly(2‐oxazoline) (POx) macro‐CTAs were synthesized through the quenching of the cationic ring‐opening polymerization (ROP) of oxazoline monomers with an anionic carbonotrithioate salt forming the POx macro‐CTA in situ, as confirmed by MALDI‐TOF MS and DOSY NMR.…”

Enabling Reversible Addition-Fragmentation Chain-Transfer Polymerization for Brush Copolymers with a Poly(2-oxazoline) Backbone

“…The clear synthetic advantages of both RAFT and CROP as well as the numerous POx-based applications mentioned show the need and motivation for combining the two polymerization methods together. The combination of CROP and RAFT has been reported previously for the synthesis of both diblock copolymers − and brush copolymers. − For brush copolymers, the recent literature includes that of Concilio et al where poly­(2-alkyl-2-oxazoline)­s were terminated on a RAFT polymerized methacrylic acid backbone to form brush copolymers exhibiting thermoresponsive behavior in oil . Similarly, Floyd et al synthesized cationic bottlebrush copolymers by grafting through vinyl groups present in poly­(2-ethyl-2-oxazoline)-based macromonomers via RAFT .…”