Styrene → Benzene, ethenyl-, polymer with 1,3-butadiene

Participants

Reaction Steps

A one gallon stirred reactor was charged with 1,800 g. of purified cyclohexane and heated to 70° C. A trace of diphenylethylene (0.2 g) was added to the cyclohexane by means of a hypodermic needle. A solution of secbutyllithium in cyclohexane was added to the reactor portionwise until a permanent orange-yellow color was obtained. The solution was then backtitrated with cyclohexane until the color just disappeared. The solvent and reactor were now ready for the polymerization of monomer. Into the closed reactor was charged 13.7 m moles of secbutyllithium and 308 g of styrene and the reactor held at 60° C. for 20 minutes. Analysis of the solution by U.V. analysis showed that less than 0.01% by weight of the styrene monomer remained. Number average molecular weights (Mn) of the polystyrene blocks were determined by Gel Permeation Chromatography to be 28,000. At this point, 361 g of butadiene was added to the reactor and the whole mixture held for 60 minutes to complete the polymerization of the butadiene. The diblock arms thus formed were analyzed by refractive index and found to be 46% by weight styrene and 54% butadiene. There was then added 15.7 ml of divinylbenzene of 55% purity and the whole was held for 75 minutes at 70° C. to complete the linking reaction. The system was terminated by the addition of 1 g of methanol. The polymer solution was transferred to a 5 gallon polyethylene liner, diluted further with acetone and the polymer was precipitated by adding isopropanol under high speed stirring. The polymer was then treated with 0.5 part Polygard HR, a commercial antioxidant, and 0.5 part 2,6, ditert-butyl-4-methylphenol per 100 parts by weight of polymer. The wet polymer was dried at 50° C. in an oven under vacuum at less than 100 microns of mercury.

Provenance & Evidence