Living Coupling Reaction in Living Cationic Polymerization. 1. Coupling Reaction of Living Polyisobutylene

Abstract

The living coupling reaction of living polyisobutylene (PIB), prepared by the 2,4,4-trimethyl-2-chloropentane/TiCl4/hexane:methyl chloride (60:40, v:v)/-80 °C system, has been studied using 1,3bis(1-phenylethenyl)benzene (MDDPE), 2,2-bis[4-(1-phenylethenyl)phenyl]propane (BDPEP), and 2,2bis[4-(1-tolylethenyl)phenyl]propane (BDTEP) as coupling agents. The reaction of living PIB with MDDPE yielded the monoadduct, possibly due to delocalization of positive charge over the meta-substituted benzene ring upon monoaddition and thereby decreased reactivity of the second double bond. Using BDPEP and BDTEP which have two diphenylethylene (DPE) moieties separated by an electron-donating spacer group, rapid and quantitative coupling was achieved independently of the chain length of the original PIB. The coupled product exhibited doubled molecular weight and narrowed molecular weight distribution. Direct evidence of the quantitative coupling reaction was also obtained by comparison of the 1 H NMR spectra of the samples before and after the coupling reaction. Kinetic studies by 1 H NMR spectroscopy indicated the coupling reaction of living PIB by BDPEP is a consecutive reaction where the second addition is faster than the first one. By kinetic treatment of the experimental results, it was found that the second addition is about 5 times faster than the first one. As a result, high coupling efficiency was also observed when excess BDPEP was used.

Synthesis of miktoarm star (?-star) polymers

“…Faust and coworkers 58 HIGHLIGHT with MDDPE leads to the monoadduct, possibly due to delocalization of a positive charge over the meta-substituted benzene. With BDPED and BDTEP, which have two DPE moieties separated by an electron-donating spacer, a rapid and quantitative coupling reaction was achieved independently of the molecular weight of the precursor PIB.…”

Synthesis of Polyisobutylene-Based Block Copolymers with Precisely Controlled Architecture by Living Cationic Polymerization

“…Several coupling agents for living poly(vinyl ethers) and PaMeSt have been reported in cationic polymerization [65][66][67], but quantitative coupling was limited to the living polymers with low molecular weight (DPn~10). We have recently extended the concept of capping reaction to coupling reaction of living PIB using bis-DPE and bis-furanyl compounds [68,69].…”

“…Synthetic utilization of non-(homo)polymerizable diolefins has been first shown for the coupling reaction of living PIB [69,70]. Using 2,2-bis[4-(1-phenylethenyl)phenyl]propane (BDPEP) or 2,2-bis[4-(1-tolylethenyl)phenyl]propane (BDTEP) as a coupling agent (Scheme 6), a rapid and quantitative coupling reaction of living PIB (Scheme 7) was achieved, independently of the molecular weight of PIB.…”

“…The coupling reaction of living PIB using bis-DPE compounds such as BDPEP or BDTEP as coupling agents has been presented above [69]. It was also conceived that bis-DPE compounds could be useful as "living" coupling agents for living PIB.…”

Synthesis of well-defined functionalized polymers and star branched polymers by means of living anionic polymerization using specially designed 1,1-diphenylethylene derivatives

“…In fact, Faust et al have synthesized A 2 B 2 heteroarm star polymers by linking two equivalents of the cationic living polymer of isobutylene with 2,2-bis[4-(1-tolylethenyl)phenyl]propane (26), followed by initiating the living cationic polymerization of methyl vinyl ether. [46] Typical results for these heteroarm star polymers are summarized in Tab. 9.…”