Efficient Synthesis of Cyclic Poly(ethylene glycol)s under High Concentration Conditions by the Assistance of Pseudopolyrotaxane with Cyclodextrin Derivatives

Chun-Lin Xiao; Yuichiro Kobayashi; Yoshihiro Tsuji; Akira Harada; Hiroyasu Yamaguchi

doi:10.1021/acsmacrolett.3c00527

Efficient Synthesis of Cyclic Poly(ethylene glycol)s under High Concentration Conditions by the Assistance of Pseudopolyrotaxane with Cyclodextrin Derivatives

ACS Macro Lett. 2023 Nov 21;12(11):1498-1502. doi: 10.1021/acsmacrolett.3c00527. Epub 2023 Oct 24.

Authors

Chun-Lin Xiao¹, Yuichiro Kobayashi^{1

2

3}, Yoshihiro Tsuji¹, Akira Harada⁴, Hiroyasu Yamaguchi^{1

2

3}

Affiliations

¹ Department of Macromolecular Science, Graduate School of Science Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan.
² Innovative Catalysis Science Division, Institute for Open and Transdisciplinary Research Initiatives (ICS-OTRI) Osaka University, 2-1 Yamada-oka, Suita, Osaka 565-0871, Japan.
³ Project Research Center for Fundamental Sciences, Graduate School of Science Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan.
⁴ The Institute of Scientific and Industrial Research Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan.

PMID: 37874266
DOI: 10.1021/acsmacrolett.3c00527

Abstract

An efficient synthesis of cyclic polymers (CPs) is in high demand due to their unique properties. However, polymer cyclization generally occurs at low concentrations (0.1 g/L), and the synthesis of CPs at high concentrations remains a challenge. Herein an efficient cyclization of poly(ethylene glycol) (M_n = 2000 g/mol, 4000 g/mol) (PEG-2k, PEG-4k) in high concentration (80 g/L) is realized by the assistance of pseudopolyrotaxane (pPRx). Water-soluble pPRx with a U-like-shape inclusion motif is prepared by mixing the 2-hydroxypropyl-γ-cyclodextrin (HPγCD) and PEG with (E)-3,4,5-trimethoxycinnamate (TCA-PEG-2k, TCA-PEG-4k). Subsequent irradiation of the pPRx solution (10-80 g/L) by UV light gives cyclic polymers through the intramolecular [2 + 2] photocycloaddition of the cinnamoyl moieties. The photoreaction of TCA-PEG-2k in the pPRx system gives cyclic monomers (C-1mer) as major products with a yield of 66% at 80 g/L. Additionally, the cyclization of TCA-PEG-4k also gives C-1mer as major products with a yield of 45% at a concentration of 80 g/L.