期刊
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
卷 144, 期 13, 页码 6080-6090出版社
AMER CHEMICAL SOC
DOI: 10.1021/jacs.2c01337
关键词
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资金
- JSPS KAKENHI [19K05582]
- Iketani Science and Technology
- Ogasawara Foundation for the Promotion of Science and Engineering
- Sumitomo Foundation
- Kyoto Technoscience Center
- Ube Industries Foundation
- Noguchi Institute
- Analytical Instrument Facility, Graduate School of Science, Osaka University
- Grants-in-Aid for Scientific Research [19K05582] Funding Source: KAKEN
By packing the substituents in the empty spaces between the side chains, the thermal stability of pi-stacked helical poly(quinolylene-2,3-methylene) is significantly improved. The amino acid substituents stabilize the pi-stacked structure and also affect the polymerization behavior.
Molecular design involving the incorporation of an alpha-amino acid residue into the side chain or main chain of apolymer is often used to stabilize artificial molecular architecturesthrough intramolecular hydrogen bonding. However, this molec-ular design strategy rarely considers the importance of interactionsbetween substituents at the alpha-position of amino acid moieties, asfound in nature. Herein, we report the synthesis of a novel series of pi-stacked helical poly(quinolylene-2,3-methylene) with amino acidderivatives bearing different substituents at the alpha-position. Wefound that the thermal stability of pi-stacked helical poly-(quinolylene-2,3-methylene) is significantly improved by packingthe substituents in the empty spaces between the side chains. Inparticular, when a bulky cyclohexyl alanine derivative was used asthe side chain, the pi-stacked helical structure maintained its stability even in dimethylsulfoxide, a hydrogen bond competitor. Thestabilization of the pi-stacked structure by the amino acid substituents resulted in a unique polymerization behavior involvingnucleation-elongation steps. In the case of derivatives with leucine and cyclohexyl alanine, which form stable pi-stacked helicalstructures, metastable structures with entangled main chains were formed in the initial polymerization stage. These structuressubsequently underwent an irreversible structural change to achieve a thermodynamically stable helical pi-stacked conformation as anucleus for subsequent polymerization. Thereafter, the polymerization reaction proceeded with the elongation of the pi-stackedhelical structure. Differences in the stability of these systems indicated that the amino acid substituents on the side chains determinethe most thermodynamically stable pi-stacked helical structure.
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