Cationic polymerization of isobutylene at room temperature

Abstract

This review highlights recent approaches toward polyisobutylene (PIB) by an energy efficient room temperature cationic polymerization. Special focus is laid on our own work using modified Lewis acids and nitrile-ligated metal complexes associated with weakly coordinating anions. In both cases, suitable conditions have been found for efficient production of PIB characterized by medium to low molar masses and a high content of exo double bonds as end groups-the typical features of highly reactive PIB, an important commercial intermediate toward oil and gasoline additives. These and other approaches demonstrate that the cationic polymerization of isobutylene is still not fully explored, and new innovative catalyst systems can lead to surprising results of high commercial interest.

A New Insight into the Mechanism of 1,3‐Dienes Cationic Polymerization I: Polymerization of 1,3‐Pentadiene with tBuCl/TiCl4 Initiating System: Kinetic and Mechanistic Study

“…The discrepancy between the branching mechanisms proposed in this work (consecutive “grafting onto” and “grafting from”) and in a recent publication by Peruch and co‐workers for the cationic polymerization of isoprene using the 2‐cyclohexylidene ethanol/B(C 6 F 5 ) 3 initiating system (only “grafting from”) could be explained by the quite low initiation efficiency of 2‐cyclohexylidene ethanol, as well as by the relatively slow polymerization. Under these conditions, the protonation of the mid‐chain double bond (such kinds of processes were recently observed for the exo ‐olefin‐terminated polyisobutylenes), followed by the “grafting from” reaction is highly probably. In addition, it was shown also that the use of a high excess of initiator toward Lewis acid ([ t BuCl]/[TiCl 4 ] > 10) influenced the number‐average molecular weight slightly but led to significant decrease of values and, most important, polydispersity (especially at low temperatures) due to the chain transfer to t BuCl (reaction III, in Scheme ).…”

“…The discrepancy between the branching mechanisms proposed in this work (consecutive "grafting onto" and "grafting from") and in a recent publication by Peruch and co-workers [ 9 ] for the cationic polymerization of isoprene using the 2-cyclohexylidene ethanol/B(C 6 F 5 ) 3 initiating system (only "grafting from") could be explained by the quite low initiation effi ciency of 2-cyclohexylidene ethanol, as well as by the relatively slow polymerization. Under these conditions, the protonation of the mid-chain double bond (such kinds of processes were recently observed for the exo -olefi n-terminated polyisobutylenes [ 50 ] ), followed by the "grafting from" reaction is highly probably.…”

Taming the Cationic Beast: Novel Developments in the Synthesis and Application of Weakly Coordinating Anions

“…[136] Thed evelopment of the asymmetric hydrogenation of unfunctionalized olefins has seen significant development of chiral Crabtree-type catalysts, which often are cationic and feature aWCA as the supporting counterion;this area has been reviewed recently. [415] Theuse of WCA precursors to effect the formation of cationic transition-metal silylenes through abstraction of halides,p seudohalides,o ra lkyl substituents permitted the [405] 2011 Inorganic/organometalliccatalysts and initiators involving weakly coordinating anions for isobutene polymerisation [406] 2013 Cationic Polymerization of IsobutyleneatR oom Temperature [407] 2014 DevelopmentofCatalysts and Ligands for Enantioselective Gold Catalysis [408] Angewandte Chemie Reviews discovery of an alternative mechanism of hydrosilylation (Scheme 20). [415] Theuse of WCA precursors to effect the formation of cationic transition-metal silylenes through abstraction of halides,p seudohalides,o ra lkyl substituents permitted the [405] 2011 Inorganic/organometalliccatalysts and initiators involving weakly coordinating anions for isobutene polymerisation [406] 2013 Cationic Polymerization of IsobutyleneatR oom Temperature [407] 2014 DevelopmentofCatalysts and Ligands for Enantioselective Gold Catalysis [408] Angewandte Chemie Reviews discovery of an alternative mechanism of hydrosilylation (Scheme 20).…”

Cationic half‐sandwich scandium complex for the synthesis of polyisobutylene with high molecular weight under mild conditions

“…Polyisobutylene and isobutylene–isoprene copolymer (IB‐IP copolymer) attracted a lot of attention in scientific research and industrial application in recent decades, because of their excellent thermal and oxidative stability, chemical resistance, biocompatibility, high hysteresis, and low permeability to gases . To obtain polyisobutylene with high molecular weight ( M n ), the cationic polymerization process of polyisobutylene‐based elastomers is always subjected to energy and environmental issues, such as the use of low temperature (–100 °C) and noxious chlorinated solvents, so the relatively high temperature procedures as well as environmental friendly systems are pursued and have been proposed elsewhere as a desirable option of great scientific interests …”