Monomers containing large alkyl groups. IV. Polymerization and properties of the polymers of 2‐alkyl‐1,3‐butadienes

The polymerization and properties of the polymers of 2‐isopropyl, 2‐ n ‐heptyl, 2‐ n ‐decyl, and 2‐ tert ‐butyl‐1,3‐butadienes are described. Second‐order transition temperatures were obtained for the 2‐alkyl‐1,3‐butadiene polymers. Poly‐2‐ n ‐heptyl‐1,3‐butadiene has a transition temperature of −83°, near that of polybutadiene. Polymers of isopropyl, tert ‐butyl, and n ‐decylbutadiene have higher transition temperatures than polyisoprene. Branched side‐chains raise the second‐order transition temperatures markedly. This is especially true of the tert ‐butylbutadiene polymer ( T m = +20°). Poly‐2‐ n ‐decylbutadiene has a transition temperature at −53° and is birefringent below −40°. From these results and those of previous workers it is apparent that sidechain branching raises the transition temperatures of poly‐2‐alkyl‐1,3‐butadienes and that low temperature flexibility cannot be materially improved over that exhibited by polybutadiene by the use of butadiene monomers containing 2‐substituted alkyl groups.