Scalable preparation and direct visualization of cyclic polymers via self-folding cyclization technique

• Published in: Science China. Chemistry 2022-12, Vol.65 (12), p.2558-2566
• Main Authors: Zhang, Hualong, Zha, Hao, Liu, Chao, Hong, Chunyan
• Format: Article
• Language: English
• Subjects: Anthracene; Chemical synthesis; Chemistry; Chemistry and Materials Science; Chemistry/Food Science; Copolymers; Ethylene glycol; Folding; Macromolecules; Microscopy; Polymers
• ISSN: 1674-7291; 1869-1870
• DOI: 10.1007/s11426-022-1344-3

Cyclic polymers exhibit distinct properties compared with their linear counterparts due to the lack of chain ends. However, the scalable synthesis of cyclic polymers remains a major challenge, especially for ring-closure method. Herein, we report a novel strategy for large-scale preparation of cyclic polymers, which relies on the prior self-folding of anthracene-telechelic amphiphilic random copolymers (poly((oligo(ethylene glycol) acrylate)- co -(dodecyl acrylate)), P(OEGA- co -DDA)) into single-chain polymeric nanoparticles (SCPNs) in water. Subsequent ultraviolet (UV)-induced cyclization occurs in the hydrophobic nano-domain. The formation of SCPNs leads to a shortened distance between the end groups of the linear precursors and spatially separated cyclization loci, and significantly enhances the efficiency of UV-induced cyclization. This self-folding technique permits access to the synthesis of cyclic polymers not only with high molecular weights ( M n > 10 5 g/mol), but also in a decent scale (40 g/L), breaking through the limitations of ring-closure method. Furthermore, the dense pendants of the copolymers can magnify the macromolecules by increasing the mass density along the backbones, thus making the polymers more readily detectable by the microscopy. The transmission electron microscopy (TEM) and atomic force microscopy (AFM) images allow us to observe the topological structures directly and provide crucial evidence to confirm the cyclization.