Efficient preparation of chemically crosslinked recyclable photodeformable azobenzene polymer fibers with high processability and reconstruction ability via a facile post-crosslinking method

• Published in: European polymer journal 2020-10, Vol.139, p.109998, Article 109998
• Main Authors: Guo, Chen, Gao, Jianfeng, Ma, Shengkui, Zhang, Huiqi
• Format: Article
• Language: English
• Subjects: Actuators; Ambient temperature; Azo compounds; Azo polymers; Chemical synthesis; Chemically crosslinked; Crosslinking; Crosslinking polymerization; Cystamine; Diamines; Fibers; Heating; Mechanical properties; Melt spinning; N-hydroxysuccinimide carboxylate; Photodeformable azobenzene polymers; Polymers; Post-crosslinking; Reconstruction; Recyclable; Recycling; Reducing agents; Solvents; Stability; Substitutes; Surface layers; Thin films
• ISSN: 0014-3057; 1873-1945
• DOI: 10.1016/j.eurpolymj.2020.109998

Efficient preparation of chemically crosslinked recyclable photodeformable azobenzene polymer fibers with high processability and reconstruction ability via a facile post-crosslinking method. [Display omitted] •Chemically crosslinked recyclable photodeformable azo polymer fibers are prepared.•The recyclable photomobile fibers have high processability and reconstruction ability.•A facile new post-crosslinking method is applied to prepare these photomobile fibers.•Highly processable side-chain azo polymers with NHS carboxylate groups are used here.•The use of cystamine as the post-crosslinker affords recyclable photomobile fibers. Chemically crosslinked recyclable photodeformable azobenzene (azo) polymer actuators with good stability (toward organic solvents and higher temperatures) and high processability and reconstruction ability hold great promise in many applications, but their development remains a challenging task. Herein, we report on for the first time a facile and highly efficient post-crosslinking method for addressing this issue. It involves first the synthesis of side-chain polymers bearing N-hydroxysuccinimide (NHS) carboxylate-substituted azo mesogens, fabrication of uniaxially oriented fibers from these azo polymers by the simple melt spinning method, and their subsequent post-crosslinking with cystamine (a diamine containing a disulfide bond) under mild conditions. The resulting chemically crosslinked fibers not only showed rapid and reversible photoinduced bending and unbending at ambient temperature as well as high mechanical strength and good solvent/heating stability, but also could be easily recycled into processable azo polymers in the presence of a reducing agent that can cleave the disulfide bond into thiol groups (i.e., tributylphosphine). In particular, the occurrence of the post-crosslinking reaction only on the thin surface layers of the azo polymer fibers afforded recycled polymers with large amounts of NHS carboxylate-substituted azo mesogens (together with a small amount of oxygen/heating-sensitive thiol-substituted ones) in the first several (at least 5) recycling processes, thus allowing highly efficient reconstruction of photodeformable fibers with excellent photomobile properties by applying melt spinning and post-crosslinking (by using cystamine) methods. The strategy presented here opens the new possibility to the facile and efficient development of various advanced chemically crosslinked recyclable photodriven actuators