Copolymerization of Butadiene and Styrene with n-Butyllithium-Polar Organic Compound Mixture and n-Butyllithium-Alkaline Metal Complex

Abstract

Copolymerizations of butadiene and styrene were investigated with n-buthllithium (BuLi)polar organic compound mixture and BuLi-alkaline metal complexes which were used as catalyst at 40°C or 50°C in n-hexane. The weight ratio of butadiene to styrene was 75: 25 and that of the monomer to solvent was 1: 4 in all cases.The polar organic compounds used were classified as follows: i) ether compounds, ii) acetallike compounds, iii) tertiary amine compouns, iv) thioether compounds and v) hetero ring compounds. When the styrene content of copolymers obtained by initiating with BuLi and polar organic compounds of group i), ii) or iii) and by terminating at 20∼60% conversion, was correlated with 1, 2-addition content of butadiene units, a fairly good linear relationship was observed among 24 compounds. While, an addition of any compound similar to thioether or hetero ring compounds to BuLi exhibited little or no effect on both the polymerization rate and the course of copolymerization.It was found that the complexes obtained by the reaction of BuLi with alkaline metals(except Na) in aromatic solvent gave random copolymers of butadiene and styrene. Copolymerizations were carried out by using the following combined catalysts with various mole ratio to BuLi: (a) BuLi-K complex, (b) BuLi-tetrahydrofuran (or diethylether) and (c) BuLi-o-dimethoxybenzene. A good linear relationship was also observed between 1, 2-addition content and styrene content of copolymers obtained, whose slopes were in the order: (a)>>(b) (cf. Fig.2).The styrene sequence distribution for a random copolymer obtained by (a) was discussed on the basis of NMR and far-infrared spectroscopic measurements. The molecular weight distribution of this copolymer was measured by gel-permeation chromatography.