The polymerization of isobutylene (IB) to yield highly reactive polyisobutylene (HR PIB) with high exo olefin content using GaCl3 or FeCl3�dialkyl ether complexes has been previously reported. In an effort to further improve polymerization rates and exo olefin content, we have studied ethyl aluminum dichloride (EADC) complexes with diisopropyl ether, 2-chloroethyl ethyl ether (CEEE) and bis-(2-chloroethyl) ether (CEE) as catalysts in conjunction with t-butyl chloride as initiator in hexanes at different temperatures. All three complexes were readily soluble in hexanes. Polymerization, however, was only observed with CEE. At 0 �C polymerization was complete in 5 min at [t-BuCl] = [EADC�CEE] = 10 mM, and resulted in PIB olefins with ~70 % exo olefin content. Studies on complexation using ATR FTIR and 1H NMR spectroscopy revealed that at 1:1 stoichiometry, a small amount of EADC remains uncomplexed. By employing an excess of CEE, exo olefin contents increased up to 90 %, while polymerization rates decreased only slightly. With decreasing temperature, polymerization rates decreased while molecular weights as well as exo olefin contents increased, suggesting that isomerization has a higher activation energy than �-proton abstraction. Density functional theory (DFT) studies on the Lewis acid�ether binding energies indicated a trend consistent with the polymerization results. The polymerization mechanism proposed previously for Lewis acid�ether complexes adequately explains all the findings. 

Highly reactive polyisobutylene by catalytic chain transfer

248th National Meeting (2014)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.