CATIONIC POLYMERIZATION OF OLEFINS AND THE STRUCTURE OF THE PRODUCT POLYMERS .2. POLY-1-BUTENE

Cationic oligomers of 1-butene (PB1) obtained under different conditions showed complicated structure by 13C-NMR investigations. Nine structural units were identified, four of which were previously unknown. At least two other new structural groups may be expected on the basis of the reaction mechanisms involved. A semiquantitative evaluation of the units constituting PB1 was developed from 13C-NMR spectra. Classical 1, 2-hydride and methide shifts, hydride transfer, and proton elimination, occurring both during the oligomer synthesis or after its formation, accounted for the structural features observed. The polymerization temperature influenced markedly PB1 composition between -20 and 120 °C; the content of branched alkyl groups increased with the reaction temperature. The features of the cationic oligomerization of 1-butene are discussed with reference to some open problems (tail-to-head or α, ω monomer addition; 1, 3-methide shift) concerning the synthesis of cationic polyolefins. © 1979, American Chemical Society. All rights reserved.