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

Abstract

This article describes the first example of an aqueous cationic polymerization that utilizes a low cost, safe, and highly recyclable initiator system (phosphotungstic acid) that retains its activity indefinitely. Quantitative yields of low to medium molecular weight polymers of p‐methoxystyrene and N‐vinylcarbazole are obtained within minutes to hours. Polymerization is first order in both monomer and phosphotungstic acid. Negatively charged surfactants suppress polymerization; whereas, nonionic soaps increase the reaction rate and reduce both polymer molecular weight and polydispersity index. Herein, the discovery of a new form of aqueous cationic polymerization involving the condensation of the alcoholic derivative of p‐methoxystyrene, 1‐(4‐methoxyphenyl)ethanol, is also disclosed.

Highly exo‐olefinic polyisobutene synthesized using a recyclable acid

“…The reader should note that such a statement is in contradiction to our view on how aqueous polymerizations that we have invented operate. [21][22][23][24][25][149][150][151] In those systems it is clear that the acid is soluble in the olefin and that it transits from the aqueous phase into the monomer droplet. Here the Brønsted acid formed from water and scandium triflate is insoluble in isobutene and thus initiation at the aqueous/organic interface as proposed by other researchers on aqueous cationic polymerizations seems more likely to occur in this instance.…”

“…31 In the current paper, we describe one example of several systems that we have developed over the past 10 years that consist of acids that retain their acidity indefinitely. 24,25,27,31 Not only are the acids described herein safe to handle, function in the absence of polar solvents, and produce relatively high MW polymers at ambient T, one is demonstrated to be easily recyclable. Furthermore, we discovered that both are capable of producing PIB with high degrees of exo-olefinic functionality, although due to time and budgetary constraints, we could not conduct a detailed study on their use for the expressed production of low MW grades of polymer that meet the proper definition of an HRPIB.…”

“…12,17,18 The corresponding author has focused on green cationic polymerizations for more than 20 years with emphasis on both isobutene and terpenes. [19][20][21] This includes aqueous polymerizations [22][23][24][25] as well as soluble 26,27 and heterogeneous [28][29][30][31] initiator systems that operate in nonpolar solvents at high T. Recently, the main goal of our group has been to develop initiator systems comprised of safer acids that function as true catalysts 25,27,31 and operate at ambient T in nonpolar media or in the absence of solvent. Although many researchers have claimed their polymerizations to be catalytic [32][33][34][35][36][37][38][39][40][41][42] only three examples of catalytic cationic polymerizations have actually been disclosed in the peer reviewed literature to date.…”

“…Although many researchers have claimed their polymerizations to be catalytic 32–42 only three examples of catalytic cationic polymerizations have actually been disclosed in the peer reviewed literature to date. These include work by: the Sawamoto group 43 on vinyl ethers using ytterbium(III) trifluoromethanesulfonate {ytterbium triflate, Yb(OTf) 3 }, Chung and coworkers on isobutene polymerization using supported BF 3 or EtAlCl 2 , 44–47 and that done in our laboratory using aqueous phosphotungstic acid for p ‐methoxystyrene (PMOS) and N ‐vinyl carbazole 25 . Although such researches represent crucial steps towards truly green cationic polymerization none provide a practical or commercially relevant means for producing polymers from isobutene, terpenes, or other olefins of lower reactivity.…”

Characterization and mechanism study of aqueous cationic polymerization of p-methylstyrene

“…Waterresistant initiators include INIURF 2,3 (acts as an initiator and surfactant), lanthanum triuoraldehyde, 1,4-10 Lewis acid surfactant combined catalyst, 7,11,12 BF 3 $OEt 2 , [13][14][15][16] aromatic borane-based co-initiators, [17][18][19][20][21][22][23][24] tris(pentauorophenyl)gallium [Ga(C 6 F 5 ) 3 ] and tris(pentauorophenyl)aluminum [Al(C 6 F 5 ) 3 ] systems, 25 and heteropoly acid and its salts. 26,27 Except the rst and seventh systems, these initiators are all co-initiators. Owing to the development of these water-resistant initiating systems, progress has been achieved in cationic polymerization, including the development of systems with high water contents and aqueous dispersion.…”