Hydrogen-Bond-Assisted Stereocontrol in the Radical Polymerization of N-Isopropylacrylamide with Secondary Alkyl Phosphate : Effect of Bulkiness of Ester Group
Hirano, Tomohiro Tokushima University Tokushima University Educator and Researcher Directory KAKEN Search Researchers
Kitajima, Hiroko Tokushima University
Ishii, Satoshi Tokushima University
Seno, Makiko Tokushima University
Sato, Tsuneyuki Tokushima University Tokushima University Educator and Researcher Directory
Radical polymerization of N-isopropylacrylamide (NIPAAm) in toluene at low temperatures was investigated in the presence of triisopropyl phosphate (TiPP). The addition of TiPP induced a syndiotactic-specificity that was enhanced by lowering polymerization temperature, whereas atactic polymers were obtained in the absence of TiPP regardless of temperature. Syndiotactic-rich poly(NIPAAm) with racemo diad = 65% was obtained at –60°C with a fourfold amount of TiPP, but almost atactic poly(NIPAAm)s were obtained by lowering temperature to –80°C. This result contrasted with the result in the presence of primary alkyl phosphates, such as tri-n-propyl phosphate, that stereospecificity varied from syndiotactic to isotactic by lowering polymerization temperature. NMR analysis at –80°C revealed that TiPP predominantly formed 1:1 complex with NIPAAm, although primary alkyl phosphates preferentially formed 1:2 complex with NIPAAm. Thus, it was concluded that a slight increase in bulkiness of the added phosphates influenced the stoichiometry of the NIPAAm-phosphate complex at lower temperatures and consequently a drastic change in the effect on stereospecificity of NIPAAm polymerization was observed.
Journal of Polymer Science Part A : Polymer Chemistry
This is the peer reviewed version of the following article: Hirano, T., Kitajima, H., Ishii, S., Seno, M. and Sato, T. (2005), Hydrogen‐bond‐assisted stereocontrol in the radical polymerization of N‐isopropylacrylamide with secondary alkyl phosphate: The effect of the bulkiness of the ester group. J. Polym. Sci. A Polym. Chem., 43: 3899-3908., which has been published in final form at https://doi.org/10.1002/pola.20883. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions.
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