Cationic polymerizations of isobutylene (IB) with H2O/FeCl3/isopropanol (iPrOH) initiating system were conducted in nonpolar hydrocarbon media, such as n-hexane or mixed C-4 fractions at -40 to 20 degrees C. This cationic polymerization is a chain-transfer dominated process via highly selective -proton elimination from CH3 in the growing chain ends, leading to formation of highly reactive polyisobutylenes (HRPIBs) with large contents (> 90 mol %) of exo-olefin end groups (structure A). The content of structure A remained nearly constant at about 97 mol % during polymerization and isomerization via carbenium ion rearrangement could be suppressed in nonpolar media. First-order kinetics with respect to monomer concentration was measured for selective cationic polymerization of IB in the mixed C-4 fraction feed at -30 degrees C and the apparent rate constant for propagation was 0.028 min(-1). High polymerization temperature (T-p) or [FeCl3] accelerate -proton elimination or isomerizations and simultaneously decrease selectivity of -proton abstraction from CH3. Molecular weight decreased and molecular weight distribution (MWD) became narrow with increasing T-p or [FeCl3]. To the best of our knowledge, this is the first example to achieve high quality HRPIBs with near 100% of exo-olefin terminals and relatively narrow MWD (M-w/M-n = 1.8) by a single-step process in nonpolar hydrocarbon media. (c) 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4200-4212

A simple but effective FeCl3-based initiating system has been developed to achieve living cationic polymerization of isobutylene (IB) using di(2-chloro-2-propyl) benzene (DCC) or 1-chlorine-2,4,4-trimethylpentane (TMPCl) as initiators in the presence of isopropanol (iPrOH) at -80 degrees C for the first time. The polymerization with near 100% of initiation efficiency proceeded rapidly and completed quantitatively within 10 min. Polyisobutylenes (PIBs) with designed number-average molecular weights (Mn) from 3500 to 21,000 g mol-1, narrow molecular weight distributions (MWD, Mw/Mn = 1.2) and near 100% of tert-Cl terminal groups could be obtained at appropriate concentrations of iPrOH. Livingness of cationic polymerization of IB was further confirmed by all monomer in technique and incremental monomer addition technique. The kinetic investigation on living cationic polymerization was conducted by real-time attenuated total reflectance Fourier transform infrared spectroscopy. The apparent constant of rate for propagation (kpA) increased with increasing polymerization temperature and the apparent activation energy (?Ea) for propagation was determined to be 14.4 kJ mol-1. Furthermore, the triblock copolymers of PS-b-PIB-b-PS with different chain length of polystyrene (PS) segments could be successfully synthesized via living cationic polymerization with DCC/FeCl3/iPrOH initiating system by sequential monomer addition of IB and styrene at -80 degrees C. (c) 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

The cationic polymerizations of isobutylene (IB) with H2O/FeCI3/dialkyl ether initiating system were conducted in dichloromethane (CH2Cl2) at temperatures from -20 to +20 degrees C, in which the dialkyl ether includes diethyl ether (Et2O), dibutyl ether (Bu2O) or diisopropyl ether (iPr(2)O). The highly reactive polyisobutylenes (HRPI I3s) with high content of exo-olefin end groups (-CH2 -C(CH3)=CH2) 82-91 mol (parts per thousand) and acceptable monornoclal molecular weight distribution (M-w/M-i = 1.7-2.3) could be successfully synthesized at low concentration of FeCI3 at 0.005 mol L-1 at 0 or even 10 degrees C. These results are comparable to those of commercial HR.PIBs produced industrially at far below 0 degrees C. The directly rapid beta-proton elimination from CH3 of the growing chain ends and chain transfer reaction to monomer were dependent on concentration of iPr(2)O.FeC13 complex (1:1), concentration of free iPr(2)O ([free iPr(2)O] = [iPr(2)O] [FeCI3]) if (iPr(2)O. FeCI3> 1) and polymerization time. The much higher concentration of PIB chains formed in the polymerization system (C-pib) than that of components in initiating system indicates a chain-transfer dominated caionic polymerization process. To the best of our knowledge, this is the first example to achieve HRPIBs with such high exo-olefin end groups by FeC13-based initiating system.

The initiating system consisting of AlCl3 with dialkyl ether such as di-n-butyl ether or diisopropyl ether has been successfully developed for providing a cost-effective process of synthesis of highly reactive polyisobutylenes (HRPIBs) with large proportion of exo-olefin end groups up to 93 mol% at temperatures ranging from -20 to +20 degrees C. The above dialkyl ethers played very important roles in promoting the directly rapid beta-proton elimination from -CH3 of the growing chain ends to create exo-olefin end groups and decreasing or even suppressing the carbenium ion rearrangements to form the double bond isomers. Very importantly, the highly reactive PIBs with 80-92 mol% of exo-olefin end groups, having low M(n)s of 1300-2300 g mol(-1) and monomodal molecular weight distribution (M-w/M-n = 1.7-2.0) could be achieved at 0-20 degrees C. These results are comparable to those of commercial HRPIBs produced industrially by the best BF3-based initiating system at far below 0 degrees C. (C) 2010 Published by Elsevier Ltd.