Basf Corporation

Patricia J Nelson

Binnur Z Gunesin

An anionic dispersion polymerization process is described for preparing linear block copolymers containing an odd number of blocks including blocks of polymerized styrenic compound, e.g., styrene, (A blocks) which are the end or terminal blocks of the polymer and which alternate along the polymer chain with elastomeric blocks of polymerized conjugated diene units (B blocks). The process includes initially contacting the total amount of styrenic compound to be utilized in forming the block copolymer under polymerization conditions with an anionic initiator and dispersant in an inert dispersion medium in which the polymer is insoluble and carrying out the process in stages wherein less than the total amount of styrenic compound is allowed to polymerize, alternating with stages wherein amounts of diene are added and allowed to polymerize completely. The addition of diene interrupts the polymerization of styrenic compound due to the greater tendency of diene to polymerize.

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Franklin Township, NY, United States of America

Patricia J Nelson