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Cationic polymerizations of isobutylene (IB) with H 2 O/FeCl 3 /isopropanol (iPrOH) initiating system were conducted in nonpolar hydrocarbon media, such as n-hexane or mixed C 4 fractions at 240 to 20C. This cationic polymerization is a chain-transfer dominated process via highly selective bproton elimination from ACH 3 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 230 C and the apparent rate constant for propagation was 0.028 min 21 .High polymerization temperature (T p ) or [FeCl 3 ] accelerate b-proton elimination or isomerizations and simultaneously decrease selectivity of b-proton abstraction from ACH 3 . Molecular weight decreased and molecular weight distribution (MWD) became narrow with increasing T p or [FeCl 3 ]. 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 5 1.8) by a single-step process in nonpolar hydrocarbon media. PIBs with >70 mol % of exo-olefin end groups (ACH 2 AC(CH 3 )@CH 2 , structure A), preferably more than 80 mol %, are normally referred to as highly reactive polyisobutylenes (HRPIBs). HRPIBs, differing from those conventional PIBs with <10% of exo-olefin end groups, have found applications as intermediates in the preparation of additives for fuels and lubricants or other further functional modification since only terminal exo-olefin in PIB chain has a sufficiently high reactivity.3,4 HRPIBs can efficiently react with maleic anhydride by direct addition reaction to synthesize PIB/maleic anhydride adducts. The high content of exo-olefin end groups and relatively narrow molecular weight distributions (MWDs) are the most important quality criteria for HRPIBs.

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 °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 (ΔEa) 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 °C. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

The synthesis of well-defined graft copolymers of poly(γ-benzyl-L-glutamate)-g-polytetrahydrofuran, PBLG-g-PTHF, has been achieved via controlled termination of living PTHF branch chains with −NH− functional groups along PBLG macromolecular backbone. The PBLG backbone with different molecular weights (M n = 2000−45000 g·mol −1 ) were prepared by anionic ring-opening polymerization of γ-benzyl-L-glutamate N-carboxyanhydrade (BLG-NCA). Living PTHF chains with predictable chain length (M n = 720−7000 g·mol −1 ) were prepared by living cationic ring-opening polymerization of THF with methyl triflate (MeOTf) as an initiator. The grafting efficiency (G E ) of living PTHF chains onto PBLG backbone via controlled termination reached to near 100%. The grafting density (G D ) along PBLG backbone and average number of PTHF branches (N b,PTHF ) in PBLG-g-PTHF graft copolymers could be mediated by changing the molar ratio of living PTHF chains to −NH− functional groups. Circular dichroism (CD) and FTIR spectra show that some of the graft copolymers maintain α-helical structure from PBLG, and the strength of CD signals for α-helical structure of the graft copolymers also decreased with increasing G D . The crystallization degree and spherulitic growth rate of the PBLG-g-PTHF graft copolymers decreased with increasing G D . The obvious phase separation and reticular state of aggregation morphology in PBLG-g-PTHF graft copolymers could be observed. PBLG-g-PTHF graft copolymers have no cytotoxicity and even conducive for cell survival. These graft copolymers had extremely low bibulous rate, and all the water absorption ratios were kept around 1.02 to maintain the shape and dimensional stability.

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