Model Studies of Alkyl Halide Activation and Comproportionation Relevant to RDRP in the Presence of Cu0

Catalytic Halogen Exchange in Miniemulsion ARGET ATRP: A Pathway to Well-Controlled Block Copolymers

Halogen exchange in atom transfer radical polymerization (ATRP) is an efficient way to chain-extend from a less active macroinitiator (MI) to a more active monomer. This has been previously achieved by using CuCl/L in the equimolar amount to P_n -Br MI in the chain extension step. However, this approach cannot be effectively applied in systems based on regeneration of activators (ARGET ATRP), since they operate with ppm amounts of catalysts. Herein, a catalytic halogen exchange procedure is reported using a catalytic amount of Cu in miniemulsion ARGET ATRP to chain-extend from a less active poly(n-butyl acrylate) (PBA) MI to a more active methyl methacrylate (MMA) monomer. Influence of different reagents on the initiation efficiency and dispersity is studied. Addition of 0.1 m NaCl or tetraethylammonium chloride to ATRP of MMA initiated by methyl 2-bromopropionate leads to high initiation efficiency and polymers with low dispersity. The optimized conditions are then employed in chain extension of PBA MI with MMA to prepare diblock and triblock copolymers.

Translating Surface-Initiated Atom Transfer Radical Polymerization into Technology: The Mechanism of Cu0-Mediated SI-ATRP under Environmental Conditions

The exceptional features of Cu⁰-mediated surface-initiated atom transfer radical polymerization (Cu⁰ SI-ATRP), and its potential for implementation in technologically relevant surface functionalizations are demonstrated thanks to a comprehensive understanding of its mechanism. Cu⁰ SI-ATRP enables the synthesis of multifunctional polymer brushes with a remarkable degree of control, over extremely large areas and without the need for inert atmosphere or deoxygenation of monomer solutions. When a polymerization mixture is placed between a flat copper plate and an ATRP-initiator-functionalized substrate, the vertical distance between these two overlaying surfaces determines the tolerance of the grafting process toward the oxygen, while the composition of the polymerization solution emerges as the critical parameter regulating polymer-grafting kinetics. At very small distances between the copper plate and the initiating surfaces, the oxygen dissolved in the solution is rapidly consumed via oxidation of the metallic substrate. In the presence of ligand, copper species diffuse to the surface-immobilized initiators and trigger a rapid growth of polymer brushes. Concurrently, the presence and concentration of added Cu^II regulates the generation of Cu^I-based activators through comproportionation with Cu⁰. Hence, under oxygen-tolerant conditions, the extent of comproportionation, together with the solvent-dependent rate constant of activation (k_act) of ATRP are the main determinants of the growth rate of polymer brushes.

Light-Controlled Radical Polymerization: Mechanisms, Methods, and Applications

The use of light to mediate controlled radical polymerization has emerged as a powerful strategy for rational polymer synthesis and advanced materials fabrication. This review provides a comprehensive survey of photocontrolled, living radical polymerizations (photo-CRPs). From the perspective of mechanism, all known photo-CRPs are divided into either (1) intramolecular photochemical processes or (2) photoredox processes. Within these mechanistic regimes, a large number of methods are summarized and further classified into subcategories based on the specific reagents, catalysts, etc., involved. To provide a clear understanding of each subcategory, reaction mechanisms are discussed. In addition, applications of photo-CRP reported so far, which include surface fabrication, particle preparation, photoresponsive gel design, and continuous flow technology, are summarized. We hope this review will not only provide informative knowledge to researchers in this field but also stimulate new ideas and applications to further advance photocontrolled reactions.

Ultrafast SET-LRP of hydrophobic acrylates in multiphase alcohol–water mixtures

A multiphase SET-LRP system using thein situgenerated Cu(0) by reduction of Cu(ii)Br₂with NaBH₄in various alcohols containing water was developed and used for SET-LRP of hydrophobic acrylates. From left to right: a solution of methanol/water containing Cu(ii)Br₂, the same solution after addition of BA and its SET-LRP.