Anionic Syntheses of Elastomers: Milestones and Recent Advances

The science and technology of the modern anionic solution polymerization of dienes and styrene to form elastomers can be traced back to the pioneering patents for the anionic polymerization of isoprene with sodium metal by Mathews and Strange in England (1910) and by Harries (1913) in Germany.  Another milestone was the report by Stavely and coworkers (1956) at Firestone describing the unique ability of lithium metal to generate high cis-polyisoprene.  That same year, Professor Michael Szwarc and coworkers clearly enunciated the living nature of the anionic polymerizations of styrene and dienes.   Although Szwarc and coworkers showed the ability to prepare block copolymers by sequential monomer addition, it was the Milkovich and Holden at Shell Development Company who first synthesized styrene-diene-styrene block copolymers and discovered their amazing properties (1966).  Dale Meier (1969), also at Shell, developed the first theory of microphase separation to explain the properties of these unique materials.  With these pioneering methodologies, it is possible to synthesize elastomers with control of the major variables affecting polymer properties.  In addition to providing insight into this background, recent advances in elastomer synthesis by anionic polymerization will be highlighted, especially new methods for the preparation and properties of functionalized elastomers.