Isoprene → Isoprene butadiene

Participants

Reaction Steps

A 3-arm star isoprene/butadiene block copolymer was synthesized using standard high vacuum techniques, M. Morton et al., J. Rubber Chem. and Technol., 48, 359 (1975). A brief summary of the polymerization procedure is as follows: Ampules containing sec-butyl lithium solution (in benzene) and benzene were released into a 250 ml all-glass high-vacuum apparatus, magnetic stirring was commenced, and sufficient isoprene was added from an ampule to form oligomeric chains five (5) units long. After stirring for 40 hours at 25° C., the mixture was frozen, and an amount of butadiene was distilled into the reaction mixture to add a block of 95 units to the living isoprene oligomers. The reaction mass was then thawed and stirred for 60 hours at room temperature. During this time, a slight increase in viscosity was noted, but the mixture remained clear and water-white. At this point, the living chains were linked with a stoichiometric amount of trichloromethyl silane, followed by precipitation into methanol. Work-up was completed by redissolution of the polymer into hexanes, washing the solution three times with water, drying the solution over MgSO4, and finally removal of the solvent using a Rotovap.

Provenance & Evidence