A UV‐Cleavable Bottlebrush Polymer with o‐Nitrobenzyl‐Linked Side Chains

Abstract

An ultraviolet (UV)-cleavable bottlebrush polymer is synthesized using the "grafting-onto" strategy by combining living radical polymerization and copper-catalyzed azide-alkyne cycloaddition (CuAAC). In this approach, reversible addition-fragmentation chain transfer polymerization is used to prepare a poly(methylacrylate) backbone with azide side groups, while atom transfer radical polymerization is employed to prepare polystyrene (PS) side chains end-functionalized with o-nitrobenzyl (UV-cleavable) propargyl groups. CuAAC is then used to graft PS side chains onto the polymer backbone, producing the corresponding bottlebrush polymers with UV-cleavable PS side chains. The formation of the bottlebrush polymer is characterized by H nuclear magnetic resonance spectroscopy, gel permeation chromatography (GPC), and Fourier transform infrared spectroscopy. The cleavage behavior of the bottlebrush polymer is monitored in tetrahydrofuran solution under UV irradiation by GPC and viscosity measurements.

Clip Chemistry: Diverse (Bio)(macro)molecular and Material Function through Breaking Covalent Bonds

“…206,290,291 Similar types of cleavage reactions have been leveraged to disassemble dendrimers 292 and bottlebrush polymers. 293 The side chains and ends of polymers can also be modified with o-nitrobenzyl groups, which can be used to modify polymer hydrophobicity or charge, translating to observable macroscopic property differences. 294,295 Clip reactions in this context yield responses such as full decomposition of the material to small fragments/individual monomers, changes in self-assembly, or generation of optical responses that can be readily visualized.…”

“…In such systems, external stimuli such as UV light can induce clip reactions throughout polymer backbones, branch points, side chains, or chain ends . For example, and as noted above in Figure , the introduction of UV-labile o -nitrobenzyl groups at the junction of block copolymers can be used for the light-mediated cleavage of different blocks. ,, Similar types of cleavage reactions have been leveraged to disassemble dendrimers and bottlebrush polymers . The side chains and ends of polymers can also be modified with o -nitrobenzyl groups, which can be used to modify polymer hydrophobicity or charge, translating to observable macroscopic property differences. , Clip reactions in this context yield responses such as full decomposition of the material to small fragments/individual monomers, changes in self-assembly, or generation of optical responses that can be readily visualized.…”

Molecular polymer bottlebrushes in nanomedicine: therapeutic and diagnostic applications

“…Similarly, designing the carriers not only to release cargo on demand, but also to allow them to disintegrate or degrade, may further minimise the side effects of unwanted long-term organ deposition. In that regard, several concepts have already been proposed to allow for sidechain detachment [177][178][179] or backbone degradation 66,68,70 and should be studied and refined further in vivo (or improved to suit bio applications). Similarly, assembled nanoparticles can be disassembled via reversible crosslinking chemistries.…”

Design, Synthesis, and Self‐Assembly of Janus Bottlebrush Polymers

“…[5][6][7] The initial synthesis of bottlebrush polymers was reported in the 1980s. [8,9] Until now, grafting-from (backbone-first), [10,11] grafting-to (backbone-first), [12,13] and grafting-through (side-chain-first) [14,15] approaches have been developed to prepare a series of bottlebrush polymers ( Figure 1A). According to the architecture, bottlebrush polymers are basically classified into homo-, [16,17] block-, [18,19] random-, core-shell-, [20,21] and Janus-types [22,23] ( Figure 1B).…”