Abstract
Polymerization of methacrylates with t-butyllithium/bis(2,6-di-t-butylphenoxy)methylaluminum in toluene at low temperature gives heterotactic polymers which comprise an alternating sequence of meso (m) and racemo (r) diads. In this paper, the effect of addition of non-polymerizable esters on the stereoselectivity in heterotactic polymerization was examined. In the polymerization of methyl methacrylate, the addition of either bulky or less bulky esters scarcely affects the stereoselectivity of propagating anions. In contrast, the addition of bulky esters such as ethyl pivalate in the polymerization of ethyl methacrylate (EMA) increased heterotactic-selectivity of m-ended anions slightly without sacrificing high heterotactic-selectivity of r-ended anions, while the addition of less bulky esters such as ethyl isobutyrate decreased heterotactic-selectivity of r-ended anions drastically with a slight increase in heterotactic-selectivity of m-ended anions. The use of ethyl pivalate as a component of mixed solvent with toluene at −95°C improved stereoselectivity of both m-ended and r-ended anions, giving heterotactic poly(EMA) with mr=94%.
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Hirano, T., Kitayama, T. & Hatada, K. Effect of Ester Compounds on Stereospecificity in Methacrylate Polymerization with t-Butyllithium/Bis(2,6-di-t-butylphenoxy)methylaluminum. Polym J 30, 736–742 (1998). https://doi.org/10.1295/polymj.30.736
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DOI: https://doi.org/10.1295/polymj.30.736