Polymerization of 1,3-dienes containing functional groups: 8. Free-radical polymerization of 2-triethoxysilyl-1,3-butadiene

The presence of a bulky substituent at the 2-position of 1,3-butadiene derivatives is known to affect the polymerization behavior and microstructure of the resulting polymers. Free-radical polymerization of 2-triethoxysilyl-1,3-butadiene (1) was carried out under various conditions, and its polymerization behavior was compared with that of 2-triethoxymethyl- and other silyl-substituted butadienes. A sticky polymer of high 1,4-structure (E : Z approximate to 8 : 2) was obtained in moderate yield by 2,2'-azobisisobutyronitrile (AIBN)-initiated polymerization. A smaller amount of Diels-Alder dimer was formed compared with the case of other silyl-substituted butadienes. The rate of polymerization (R-p) was found to be R-p = k[AIBN](0.5)[1](1.2), and the overall activation energy for polymerization was determined to be 117 kJ mol(-1). The monomer reactivity ratios in copolymerization with styrene were r(1) = 2.65 and r(st) = 0.26. The glass transition temperature of the polymer of 1 was found to be -78 degrees C. Free-radical polymerization of 1 proceeded smoothly to give the corresponding 1,4-polydiene. The 1,4-E content of the polymer was less compared with that of poly(2-triethoxymethyl-1,3-butadiene) and poly(2-triisopropoxysilyl-1,3-butadiene) prepared under similar conditions. (C) 2010 Society of Chemical Industry