Controlled Catalytic Chain Transfer Polymerization of Isobutylene in the Presence of tert-Butanol as Exo-Enhancer

Abstract

Catalytic chain transfer polymerization (CCTP) of isobutylene in the presence of alcohol as an exo-enhancer with tert-butyl chloride/ethylaluminum dichloride (EADC)·bis­(2-chloroethyl) ether (CEE) has been investigated in hexanes at 0 °C. Increasing exo-olefin content was observed with increasing steric bulkiness of the alkyl group of the alcohol, i.e., tert-butyl > isopropyl > methyl. Here, we report that tert-butanol (t-BuOH) is an excellent exo-enhancer compared to other tert-alcohols such as tert-amyl alcohol (AmOH), 2-methyl-2-pentanol (MPOH), and 3-ethyl-3-pentanol (EPOH). The aromatic tert-alcohol cumyl alcohol was not an exo-enhancer but acted as an initiator. In the reaction of EADC.CEE and t-BuOH, t-butoxy­aluminum dichloride (t-BuOAlCl2) was formed, which is the real exo-enhancer and is not stable at room temperature. Molecular weights were virtually unchanged in the presence t-BuOAlCl2 with [t-BuOAlCl2]:[EADC.CEE] < 0.5, and exo-olefin content increased ∼15% relative to polymerization in the absence of t-BuOAlCl2. This is presumably due to stabilization of the cation by t-BuOAlCl2 which slows isomerization of the PIB+. Stabilization of the cation was confirmed by 1H NMR and UV–vis spectroscopy at 0 °C by adding t-BuOAlCl2 to the diphenylmethyl cation, a representative stable cation. The rate constant of chain transfer (k tr) was determined to be 2 × 108 L mol–1 s–1 at 0 °C, which is not affected by t-BuOAlCl2. Addition of an exo-enhancer is especially important for polymerization at CSTR conditions at low steady state monomer concentrations. This is the first report identifying the role of alcohols in CCTP and opens new vistas in the synthesis of highly reactive polyisobutylene.

Characteristics and Mechanism of Vinyl Ether Cationic Polymerization in Aqueous Media Initiated by Alcohol/B(C6F5)3/Et2O

“…When the reaction temperature was reduced, the reaction exotherms decreased, and the preparation times increased in all suspension processes. Meanwhile, a trend contrary to traditional cationic polymerizations [1,2,3,46] was observed. The yields and M n obtained in the aqueous suspension processes decreased when the reaction temperature was lowered.…”

“…CumOH/B(C 6 F 5 ) 3 /Et 2 O induced polymerization in a reproducible manner in the suspension and emulsion. The second feature was about the decrease in monomer conversion and M n when the reaction temperature was reduced using B(C 6 F 5 ) 3 as a co-initiator; this process was contrary to traditional cationic polymerizations [1,2,3,46]. The third feature was that low yields and M n were obtained in n -hexane/H 2 O, toluene/H 2 O, NaCl solution, and emulsion in comparison with high-purity water; this process was opposite to the aqueous cationic polymerizations using other co-initiators [26,27,28,37].…”

“…Conventional cationic polymerizations of vinyl monomers, such as isobutylene (IB), vinyl ethers, and styrene, are usually achieved by using initiator/co-initiator systems primarily in chlorinated solvents under low-temperature and strict water-free conditions [1,2,3,4,5,6,7,8]. Chlorinated solvents seriously damage the environment, and their applications should be limited [9,10].…”

Synthesis of comb‐like dispersants and a study on the effect of dispersant architecture and carbon black dispersion

“…The current method for the synthesis of PIBSI dispersants starts with the preparation of PIB with olefinic end groups through the acid‐catalyzed (AlCl 3 , BF 3 , and BF 3 complexes) polymerization of isobutylene (IB) . Development of new catalysts and catalyst complexes and more cost‐effective processes for the production of highly reactive (HR) PIB are currently active areas of research . Formation of PIB succinic anhydride (PIBSA) is accomplished by reaction of olefin‐terminated PIB with maleic anhydride (MAH), which occurs by either a chlorine‐mediated Diels–Alder reaction (traditional PIB derived from AlCl 3 catalyst) or a thermal ene reaction at temperatures greater than 200 °C (HR PIB derived from BF 3 catalyst) .…”

“…[11][12][13] Development of new catalysts and catalyst complexes and more cost-effective processes for the production of highly reactive (HR) PIB are currently active areas of research. [14][15][16][17][18][19][20] Formation of PIB succinic anhydride (PIBSA) is accomplished by reaction of olefin-terminated PIB with maleic anhydride (MAH), which occurs by either a chlorine-mediated Diels-Alder reaction (traditional PIB derived from AlCl 3 catalyst) or a thermal ene reaction at temperatures greater than 200 C (HR PIB derived from BF 3 catalyst). 9,10 Imidization of PIBSA with heavy polyamines, such as triethylene tetramine and tetraethylenepentamine (TEPA), is then carried out to form the PIBSI dispersant.…”