A new method to separate the homopolymer from butadiene-styrene copolymerization product, a "two -layer extraction method," has been developed .Many new catalyst systems and copolymerization techniques (random, block or graft etc.) have previously been employed in the preparation of the butadiene-styrene copolymer.It is important to characterize these products and identify the copolymer in the light of the evaluation of catalyst systems, copolymerization methods, and the physical properties of the products. Several solvent-extraction methods and fractional extraction methods have been employed in order to verify the existence of the copolymer and to separate a homopolymer from the copolymerization product. By these methods, however, a quantitative treatment was difficult. Moreover, the selection of a solvent and a nonsolvent was troublesome.We have now succeeded in making a quantitative separation of the homopolymer from copolymerization products by a "two-layer extraction method," using n-hexane and N, N-dimethylformamide (DMF); the separation is accompanied by a dioxane extraction.The butadiene-styrene copolymerization product (1.0g) was dissolved or suspended in n-hexane (200ml) under stirring for ca. 50hr; then the solution or the suspension was placed in a 500ml separating funnel and 100ml of DMF was added. The funnel was shaken for ca. 15min and then left standing for 1hr, after which two layers, (the n-hexane layer(upper) and the DMF layer (lower)), were separated. The polymer (A) dissolved in the DMF layer and the polymer (B) dissolved or suspended in the n-hexane layer were isolated and dried under a vacuum. The polymer (B) was then further extracted with dioxane to

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