EFFECT OF ESTER COMPOUNDS ON STEREOSPECIFICITY IN METHACRYLATE POLYMERIZATION WITH T-BUTYLLITHIUM BIS(2,6-DI-T-BUTYLPHENOXY)METHYLALUMINUM/

Polymerization of methacrylates with yllithium/bis(2,6-di-t-butylpheno xy)methylaluminum in toluene at law temperature gives heterotactic pol ymers which comprise an alternating sequence of meso (m) and racemo (r ) diads. In this paper, the effect of addition of non-polymerizable es ters on the stereoselectivity in heterotactic polymerization was exami ned. In the polymerization of methyl methacrylate, the addition of eit her 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) in creased heterotactic-selectivity of m-ended anions slightly without sa crificing high heterotactic-selectivity of r-ended anions, while the a ddition of less bulky esters such as ethyl isobutyrate decreased heter otactic-selectivity of r-ended anions drastically with a slight increa se in heterotactic-selectivity of m-ended anions. The use of ethyl piv alate as a component of mixed solvent with toluene at -95 degrees C im proved stereoselectivity of both m-ended and r-ended anions, giving he terotactic poly(EMA) with mr = 94%.