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

The anionic polymerization of 2,3-diphenyl-1,3-butadiene (1) was investigat ed 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 cumylpotas sium or s-BuLi to afford quantitatively the polymers of well-controlled mol ecular weights and narrow molecular weight distributions (M-w/M-n < 1.1). E ach 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 poly mer consisted of 90% cis and 10% trans 1,4-structures, although the assignm ent 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 poly mer precipitated completely from the polymer solution in THF. The polymer t hus precipitated became insoluble in most organic solvents except for hot t oluene and o-dichlorobenzene. This may therefore be due to the crystallizat ion of the polymer, but not cross-linking as previously reported.