Aqueous cationic olefin polymerization using tris(pentafluorophenyl)gallium and aluminum

Abstract

Tris(pentafluorophenyl)gallium (3) and aluminum (7) are active coinitiators for the production of medium‐high molecular weight (MW) polymers of styrene and isobutene (IB) under aqueous reaction conditions. Strong Brønsted acids formed in situ by reaction of these coinitiators with background moisture present in the monomer droplet (5 and 8, respectively) are believed to be responsible for inducing cationic polymerization of these monomers. Of the two, 7 is the most active for IB polymerization in both aqueous media and anhydrous aliphatic solvents. These results are in contradistinction to tris(pentafluorophenyl)boron (2), which is incapable of polymerizing IB in aqueous or aliphatic media. The MWs of the polyisobutenes (PIBs) produced under aqueous conditions by either coinitiator greatly exceed those formed under similar reaction conditions by the strongly acidic chelating diborane (1,2‐C6F4[B(C6F5)2]2, 1) or diborole (1,2‐C6F4[9‐BC12F8]2, 6). Both 3 and 7 are readily synthesized from the corresponding Group 13 halide compounds in conjunction with bis(pentafluorophenyl)zinc (4). Aqueous polymerization of IB dissolved in aliphatic solvents with 3 or 7 can yield PIBs with relatively narrow polydispersities. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

Indefinitely active aqueous cationic polymerizations, part I: Low cost, recyclable initiator systems

“…It is important to emphasize that the MW of the polymer does not appear to depend strongly on conversion (i.e., polymerization is non‐living). These results agree with earlier aqueous polymerization systems invented by our group that are also not living . They also ramify results obtained during the emulsion polymerization of PMOS using surfactants bearing BA groups [e.g., dodecylbenzene sulfonic acid (DBSA)] and those initiated by HCl or HCl + Yb(OTf) 3 .…”

“…This was soon followed by systems based on B(C 6 F 5 ) 3 and BF 3 O·Et 2 ; however, they typically only generate low MW polymers . Our research group then used highly acidic monodentate PFLAs [i.e., Al(C 6 F 5 ) 3 and Ga(C 6 F 5 ) 3 ] with even better results . Recently, we discovered that polymerization of low reactivity olefins can be effected in an aqueous solution of a Brønsted acid [e.g., HCl(aq)] in the presence of small amounts of compounds that furnish a weakly coordinating anion [e.g., lithium bis(trifluorosulfonimide), CsCHB 11 Cl 11 , etc.]…”

A Catalyst Platform for Unique Cationic (Co)Polymerization in Aqueous Emulsion

“…Unfortunately,t hese catalysts required the use of highly concentrated electrolyte aqueous solutions as reaction media, allowing polymerizations exclusively at very low temperatures (below À40 8 8C). [13][14][15] These conditions are clearly not those of the conventional emulsion technique,aspresented here.…”

Characteristics and Mechanism of Styrene Cationic Polymerization in Aqueous Media Initiated by Cumyl Alcohol/B(C6F5)3

“…Water not only could coordinate to B(C 6 F 5 ) 3 to initiate polymerization but also could participate in chain‐transfer reactions. In such solutions with high concentration of Cl ion, hydrogen bonds between water molecules are broken, and free water molecules exist in the form of disordered network composed of ions, ion pairs, and water molecules . The presence of salt in the system enhanced the chain‐transfer to water while hampering chain propagation.…”