Carbocationic polymerization, synthesis polymerizations

G-5 Aliphatic Petroleum Resins. Carbocationic polymerization of C-5 feedstreams has been accomptished with various Friedel-Crafts catalyst systems. Table 3 compares the efficiencies of selected Lewis acids ia the polymerization of a typical C-5 stream containing 43 wt % C-5—C-6 diolefias and 47 wt % C-5—C-6 olefins (20). Based on weight percent yield of resia at equimolar coaceatratioas of catalyst (5.62 mmol/100 g), efficieacy follows AICI3 AlBr3 > BF3etherate-H20 > TiCfy > SnCl. The most commonly used catalyst in petroleum resin synthesis is AlCl. ... 

Synthesis of PIB prepolymers. fm-Chlorine-telechelic PIB (Mn=4,000 MVf/Mn 1.09) (7), and an allyl-telechelic PIB (Mn=9,500 Mw/Mn 1.14) (7,8) were prepared by living carbocationic polymerizations. The tert-chlorine ended PIB was quantitatively dehydrochlorinated (9) to -C(CH3)=CH2 terminated polymer. Both olefin-telechelic PIBs were then hydroborated and oxidized (10) to prepare the primary hydroxyl termini. The hydroxyl-telechelic polymers were esterified with methacryloyl chloride to methacrylate-telechelic PIBs, MA-PIB-MA (11). 

Quasi-living Carbocationic Polymerization of Alkyl Vinyl Ethers and Block Copolymer Synthesis... 

Matyjaszewski, K. and M. Sawamoto, Controlled/Living Carbocationic Polymerization, Chap. 4 in Cationic Polymerizations Mechanisms, Synthesis, and Applications, K. Matyjaszerski, ed., Marcel Dekker, New York, 1996. 

This review concerns the synthesis and characterization of octa-arm polyisobutylene (PIB) stars, allyl-terminated octa-arm PIB stars, and octa-arm star blocks by using a novel octafunctional caHx[8]arene-based initiator 1. Scheme 1 shows the structure of 1 and the target architectures. The syntheses were carried out under living carbocationic polymerization conditions. 

A detailed description of the sequential copolymer synthesis by carbocationic polymerization is presented in a recent book (3). 

A new method for the synthesis of polyisobutylene-based block copolymers, involving living carbocationic polymerization of isobutylene and subsequent living anionic polymerization of methacrylic monomers has been demonstrated. Di- and triblock copolymers nearly free of PIB precursor and with narrow and unimodal MWD were synthesized under well-controlled conditions. 

A new synthetic route for the synthesis poly(IB-i)-tBMA) developed by combining Hving carbocationic and anionic polymerizations involves metalation of 2-polyisobutylenyl-thiophene with n-butyUithium in THE at —40°C. The resulting stable macrocarbanion (PIB-T-, Li+) was successfully used to initiate living anionic polymerization of tBMA yielding poly(IB-i)-tBMA) block copolymers [235]. 

The existence of a dynamic equilibrium between dormant (covalent) and active (ionic) species in controlled carbocationic polymerizations had been debated for years. It has been argued that under certain conditions, polarized covalent species can directly react with monomer examples are the pseudocationic mechanism proposed for the polymerization of styrene initiated by perchloric acid (123,124) (Fig. 5) or the two-component group transfer polymerization proposed for the polymerization of isobutylene initiated by the dicumylacetate/BCls system (125) (Fig. 6). Recent results and theoretical considerations support the now generally accepted view that the true active species are ions, and the dormant species serve as a reservoir from which the propagating ion pairs are formed (126-131). The existence of a dynamic equilibrium between dormant and active species and the ability to suppress the formation of free ions made possible the synthesis of pol5miers with controlled molecular architecture via carbocationic polymerization. 

The preparation of telechelics by carbocationic polymerization (qv) of vinyl monomers (196,197) has received little attention because of the high reactivity and low selectivity of growing species. The synthesis of useful telechelics requires the control of molecular weight and end groups this was not possible imtil the discovery of living cationic poljunerization. 

Quenching of living carbocationic polymerization also leads to tert-chlorine-telechelic polyisobutylenes (222). Synthesis of mono- (223-226), di- (227-235), tri- (236), and tetrafianctional (237) polyisobutylenes carrying Cl termini was reported. 

Ivan, B. and Kennedy, J.P. (1990) Living carbocationic polymerization. XXX. One-pot synthesis of allyl-terminated linear and tri-arm star polyisobutylenes, and epoxy- and hydro xy-telechelics thereftom. Journal of Polymer Science Part A Polymer Chemistry, 28,89-104. 

In general reviews on telechelics, carbocationic polymerization of vinyl monomers has received little attention due to the high reactivity and low selectivity of the growing species. Therefore, until recently it was widely accepted that the molar mass and end group control necessary for the synthesis of usehil telechelics would not be accessible by carbocationic polymerization. This situation has changed in recent years. 

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