Anionic living polymerization of 2,3-diphenyl-1,3-butadiene

The anionic polymerization of 2,3-diphenyl-1,3-butadiene (1) was investigated in THF at -78 degrees C as well as in benzene at 40 degrees C. Compound 1 was found to undergo anionic Living polymerization in THF with cumylpotassium or s-BuLi to afford quantitatively the polymers of well-controlled molecular weights and narrow molecular weight distributions (M-w/M-n < 1.1). Each of the microstructures of the polymers was observed to be only the 1,4-addition product of poly(2,3-diphenyl-1,3-butadiene). Furthermore, the polymer consisted of 90% cis and 10% trans 1,4-structures, although the assignment of these configurations was tentative. It was observed by DSC that the polymer showed a glass transition temperature of 98 degrees C and a melting point of 170 degrees C. Surprisingly, on standing for a few hours the polymer precipitated completely from the polymer solution in THF. The polymer thus precipitated became insoluble in most organic solvents except for hot toluene and o-dichlorobenzene. This may therefore be due to the crystallization of the polymer, but not cross-linking as previously reported.