The microstructure of diene polymers. III. Polyisoprenes and polybutadienes prepared with cationic catalysts

A number of polyisoprenes and polybutadienes have been prepared at temperatures between 30° and −78°C. using Friedel‐Crafts catalysts. Quantitative analyses for the various types of addition occurring in these polymers have been made from their infrared spectra. It has been found that the linear structures corresponding to 1,4; 1,2 and 3,4 addition are present in about the same ratios as in free radical type polymers. However, in the case of the polyisoprenes (and apparently also the polybutadienes) these structures account for only about 50 to 75% of the material present.