1. Wavelength-Selective Photo-Cycloadditions of Styryl-Anthracene
Jing Bai, Zixing Shi, Xiaodong Ma, Jie Yin, Xuesong Jiang Macromol Rapid Commun. 2022 May;43(9):e2200055.doi: 10.1002/marc.202200055.Epub 2022 Apr 7.
Light-tunable covalent chemistry is highly urgent in the fields of chemistry, biology, and materials science, especially for the smart materials and surface, due to the spatiotemporal control and feasible operation. Here, a new type of wavelength-selective photo-cycloaddition of styryl-anthracene carboxylic acid (SACA) is reported. Upon the irradiation of 450 nm visible light or 365 nm UV light, SACA can undergo [2+2] or [2+4] photocycloaddition, respectively. Furthermore, the [2+2] photocycloaddition induced by vis-light of 450 nm is reversible and can be disrupted by 365 nm UV light to form dimer-24 which cannot be photo-cleavable. Owing to the feasibility and spatiotemporal characteristics of UV-vis light-controlled photocycloaddition, the SACA possesses potential applications in various areas such as self-assembly, dynamic wrinkles, and fluorescence patterns, which are also explored and exhibited in this work.
2. A UV-Cleavable Bottlebrush Polymer with o-Nitrobenzyl-Linked Side Chains
Wen Zhu, Liangcai Zhang, Yongming Chen, Ke Zhang Macromol Rapid Commun. 2017 Jun;38(11).doi: 10.1002/marc.201700007.Epub 2017 Mar 21.
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 1 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.
3. Red and Near-Infrared Light-Cleavable Polymers
Xiaolong Zeng, Xuechang Zhou, Si Wu Macromol Rapid Commun. 2018 Jul;39(14):e1800034.doi: 10.1002/marc.201800034.Epub 2018 Jul 20.
Photocleavable polymers have attracted much attention in drug delivery, photopatterning, and controlling cell behavior. Photolysis is usually induced by UV light. However, UV light cannot penetrate deeply into biological tissue and may damage biological components. Therefore, conventional UV-light-cleavable polymers are problematic for deep-tissue biomedical applications. In this feature article, red and near-infrared light-cleavable polymers are reviewed, and their potential applications are highlighted. The remaining challenges in the field of photocleavable polymers are discussed.
