Ionic Oligomerization and Polymerization of 2-Alkenyl-2-oxazolines

Abstract

ABSTRACT:Ionic RfOpagation of 2-alkenyl-2-oxazolines has been examined in the presence of both cationic and anionic initiators. In order to provide a basis for understanding the cationic (Bmnsted acid) propagation modes, model systems involving 2-alkenyl-2-oxazolinium salts and nucleophiles were studied. Spectroscopic analysis of these salts ( 13 C and 1 H NMR) predicted electrophilic activity at the 2-and 5-position of the heterocyclic ring as well as the terminal olefin carbon. Nucleophilic attack was observed at each of these positions with specificity as a function of the nucleophile type. Ketene aminal species were demonstrated to be key intermediates in the cationic propagation processes as by deuterium trapping experiments. Three new cationic propagation modes leading to dimeric or oligomeric products were identified and occurred as a function of the (a) acid strength, (b) proton multiplicity of the acid, and (c) nucleophilicity of the polymerization medium. Proposed propagation mechanisms ate discussed. Anionic polymerization of 2-isopropenyl-2-oxazoline with butyllithium was shown to give low-molecular-weight polymers which are identical to those obtained by use of radical initiators. Finally, this study demonstrates that whereas radical and anionic polymerization of 2-alkenyl-2-oxazolines involve IXcarbon propagating species, the cationic modes proceed via {3-carbon-type species.

Reactivity of Cyclic Imino Ether Salts Having Vinyl Group V. Spontaneous and Base-Catalyzed Polymerization of N-Protio Salts of 2-Alkenyl-2-oxazolines and 2-Alkenyl-5,6-dihydro-4H-1,3-oxazines

“…The polymer of Sb, on the other hand, was considered to consist exclusively of proton-transferred unit, i.e., poly[(2-oxazolinium-2,3-diylene )(ethylene)], because NH proton was not detected in the vicinity of b 8-12 in its 1 H NMR spectrum. In addition, the signals due to the ring-preserved unit were very similar to those of the oligomeric product of the ring-preserved polymerization reported by Tomalia et al 4 These polymers as well as the products of the "spontaneous" polymerization were not stable which were gelled at room temperature even under anhydrous conditions. They are soluble in DMF and DMSO, but insoluble in acetonitrile and other less-polar solvents.…”

“…On the other hand, Tomalia et al reported the interesting ring-preserved polymerization using N-protio-2-isopropenyl-2-oxazolinium * 2 To .whom inquires about the paper should be addressed. salt {Sb) (eq2), 4 which has a close similarity to the N-methyl salt. However, the N-protonated salts of other 2-alkenyl cyclic imino ethers have not been reported and, therefore, their general reactivities have not been known.…”

Synthesis of Pyridine- and 2-Oxazoline-Functionalized Vinyl Polymers by Alane-Based Frustrated Lewis Pairs

“…More drastically, replacing Al(C 6 F 5 ) 3 with B(C 6 F 5 ) 3 or AlEt 3 led to a completely inactive polymerization system (runs 8 and 9). Polymerizations employing the preformed monomer-LA adduct, (2-VP)·Al(C 6 F 5 ) 3 , afforded the results similar to those by the toluene adduct, (toluene) 0.5 ·Al(C 6 F 5 ) 3 (runs 10-13 vs. runs [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. Also noteworthy is that, when carried out in CH 2 Cl 2 or DMF, the above polymerizations were much less effective or completely shut down, attributable to rapid deactivation of Al(C 6 F 5 ) 3 in CH 2 Cl 2 15 or impeding of the monomer activation by virtue of strong coordination of DMF to Al(C 6 F 5 ) 3 .…”

Design and Preliminary Studies of Environmentally Enhanced Water-Castable, Water-Developable Positive Tone Resists: Model and Feasibility Studies

“…As a result we chose to test the water-soluble linear polymer that is obtained by free-radical polymerization of 2-isopropenyl-2-oxazoline, 1. Monomer 1 can be polymerized through a variety of techniques, as shown in Scheme 1 (6,7). Both radical or anionic polymerization conditions lead to a polymer containing pendant oxazoline rings, while a more complex structure is obtained under cationic conditions as both the vinyl and the oxazoline moieties are reactive.…”