Hydrogen-Bond-Assisted Stereocontrol in Radical Polymerization of N-Isopropylacrylamide by Using Primary Alkyl Phosphate : Effect of Chain Length of Straight Ester Group
Stereocontrol in NIPAAm polymerization
Hirano, Tomohiro Tokushima University Tokushima University Educator and Researcher Directory KAKEN Search Researchers
Ishii, Satoshi Tokushima University
Kitajima, Hiroko Tokushima University
Seno, Makiko Tokushima University
Sato, Tsuneyuki Tokushima University Tokushima University Educator and Researcher Directory
Radical polymerizations of N-isopropylacrylamide (NIPAAm) were carried out in toluene at low temperatures in the presence of phosphoric acid esters such as trimethyl, triethyl (TEP), tri-n-propyl, and tri-n-butyl phosphates (TBP). Syndiotactic-rich poly(NIPAAm)s were obtained at the temperature range from –60°C to 0°C, and particularly TEP provided the highest syndiotacticity (racemo diad = 65%) at –40°C. On the other hand, lowering temperature reversed the stereoselectivity of the propagation reaction so that isotactic-rich poly(NIPAAm)s were obtained at –80°C. In particular, TBP exhibited the most isotactic-specificity (meso diad = 57%). Job's plots for NIPAAm-TBP mixtures revealed that NIPAAm and TBP formed 1:1 complex at 0°C and predominantly 1:2 complex at –80°C through a hydrogen-bonding interaction. Therefore, it is considered that the stereospecificity of NIPAAm polymerization should depend on the stoichiometry of the hydrogen-bond-assisted complex. Thus, the mechanism for the present polymerization system was discussed.
Journal of Polymer Science Part A : Polymer Chemistry
This is the peer reviewed version of the following article: Hirano, T., Ishii, S., Kitajima, H., Seno, M. and Sato, T. (2005), Hydrogen‐bond‐assisted stereocontrol in the radical polymerization of N‐isopropylacrylamide with primary alkyl phosphate: The effect of the chain length of the straight ester group. J. Polym. Sci. A Polym. Chem., 43: 50-62., which has been published in final form at https://doi.org/10.1002/pola.20475. 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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