Molecular Polymer Brushes Made via Ring‐Opening Metathesis Polymerization from Cleavable RAFT Macromonomers

Abstract

The use of labile covalent bonds such as oximes and acetals for their application in the synthesis, and controlled triggered deconstruction, of molecular polymer brushes (MPBs) is reported. Macromonomers (MMs) are produced via reversible addition‐fragmentation chain transfer (RAFT) polymerization using chain transfer agents (CTAs) featuring customized labile moieties. Ring‐opening metathesis polymerization (ROMP) of the MMs using the grafting‐through approach produced MPBs in which the cleavable CTA is incorporated along the backbone, between the brush mainchain and its side chains. Degradation (i.e., the detachment of side chains) of the brush is possible through exposure to an acid stimulus. Especially, ketoxime, solketal, and ethoxyethyl (EE) acetal‐based motifs demonstrate excellent orthogonality to the polymerization protocols. This study highlights how polymer architectures can be built from, and reverted to, single polymer chains by using well‐designed CTAs in a straight‐forward approach.

Preparation of α,ω‐heterobifunctionalized poly(N‐vinylpyrrolidone) via a bis‐clickable RAFT reagent

“…From the 1 H NMR spectrum (Figure 1A), the characteristic signals at chemical shifts of 7.65-7.97 ppm were attributed to protons on the phenyl group, the typical peak of 4.52 ppm was attributed to protons of the methylene next to the benzene ring, and the three typical peaks of 3.43, 2.71, and 1.98 ppm were assigned to protons of the three adjacent methylene groups. In addition, the typical peaks at chemical shifts of 147.73, 130.40, and 128.71 ppm in 13 C NMR are attributed to carbon atoms on the benzene ring, and the characteristic signals of 49.73, 35.74, 31.76, and 28.78 ppm were attributed to the four methylene carbon atoms (Figure 1B). Furthermore, the characteristic peak with a chemical shift at 64.25 ppm in the 19 F NMR spectrum was attributed to the fluorine atom in the benzenesulfonyl fluoride fragment (Figure S3).…”

“…Fourier transform infrared spectroscopy (FTIR, resolution: 4 cm À1 ) was performed using a Nicolette 6700 FTIR spectrometer (Thermal Fisher Scientific, USA). 1 H, 13 C, and 19 F nuclear magnetic resonance (NMR) spectra were obtained by an Agilent Nuclear magnetic resonance spectrometer (Varian, USA). Mass spectrometry (MS) spectra were obtained using a micrOTOF-Q III instrument (Bruker, Germany).…”

“…As shown in Scheme 1, the new RAFT agent Az-FSBCT was synthesized by a one-pot method of 3-azido-1-propyl mercaptan, carbon disulfide, and 4-(bromomethyl) benzenesulfonyl fluoride. The molecular structure of the reagent was confirmed by 1 H NMR, 13 C NMR, 19 F NMR, MS, and FTIR spectra. From the 1 H NMR spectrum (Figure 1A), the characteristic signals at chemical shifts of 7.65-7.97 ppm were attributed to protons on the phenyl group, the typical peak of 4.52 ppm was attributed to protons of the methylene next to the benzene ring, and the three typical peaks of 3.43, 2.71, and 1.98 ppm were assigned to protons of the three adjacent methylene groups.…”

“…9,10 Among these polymerization techniques, the RAFT process is particularly suitable for the preparation of terminal functional polymers due to its compatibility with a broader range of monomers and reaction media. For example, terminal functional polymers with linear, 11 star, 12 brush, 13 ring, 14 and other molecular architectures have been synthesized through the design of RAFT reagent structures. 2,3 Since the concept of click chemistry was first proposed by Sharpless et al in 2001, 15 it has been widely developed due to its characteristics of high efficiency and robust, rapid, and specific reactions.…”

“…Among these polymerization techniques, the RAFT process is particularly suitable for the preparation of terminal functional polymers due to its compatibility with a broader range of monomers and reaction media. For example, terminal functional polymers with linear, 11 star, 12 brush, 13 ring, 14 and other molecular architectures have been synthesized through the design of RAFT reagent structures 2,3 …”