Synthesis and chiral recognition ability of optically active poly{N‐[(R)‐α‐methoxycarbonylbenzyl]methacrylamide} with various tacticities by radical polymerization using Lewis acids

Abstract

The radical polymerization of an optically active methacrylamide, N‐[(R)‐α‐methoxycarbonylbenzyl]methacrylamide, was carried out in the absence and presence of Lewis acids such as yittribium trifluoromethanesulfonate [Yb(OTf)3] and scandium trifluoromethanesulfonate [Sc(OTf)3]. Catalytic amounts of the Lewis acids significantly affected the stereoregularity of the obtained polymers. The polymerization with Yb(OTf)3 in tetrahydrofuran afforded isotactic polymers (up to mm = 87%), whereas the conventional radical method without the Lewis acid produced polymers rich in syndiotacticity (up to rr = 88%). The radical polymerization in the presence of MgBr2 proceeded in a heterotactic‐selective manner (mr = 63%). Thus, the isotactic, syndiotactic, and heterotactic poly(methacrylamide)s were synthesized by the radical processes. The chiral recognition abilities of the obtained optically active poly(methacrylamide)s were affected by the stereoregularity. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3354–3360, 2003

Novel Initiating System for the Stereocontrolled Radical Polymerization of Acrylamides: Alkyl Bromide/Rare Earth Metal Triflate System

“…The increase in the isotacticity of the polymer is ascribed to the effective complexation of Y(OTf) 3 with the last two pendant amide groups of the propagating radical and the incoming monomer unit which in turn favors the meso-type addition of the Lewis acid-complexed NIPAM monomer. Similar observations have been reported for the polymerization of acrylamides, 15,16,18,19,22 methacrylamides, [16][17][18][19][20][21] and methacrylates 24 in the presence of bulky lanthanide triflate Lewis acids. The increase in the EBIB concentration from 10 mM to 30 mM (entries 3, 5 and 6) while keeping other conditions the same increases the polymer yield, decreases the molecular weight of the polymer, and increases the polydispersities.…”

“…[15][16][17][18][19][20][21][22] The Lewis acids further affected the stereochemistry of the polymers. Especially, for the acrylamides, highly isotactic polymers were obtained with rare-earth metal triflates.…”

Synthesis, Chiroptical Properties, and Chiral Recognition Ability of Optically Active Polymethacrylamides Having Various Tacticities

“…On the other hand, Lewis acids interact with the monomers and the propagating chain-end to change the stereochemistry of the polymerization to isotactic-selective manner. 1 In our previous study, 5 the polymerization of N-[(R)--methoxycarbonylbenzyl]methacrylamide ((R)-1) in the presence of Yb(OTf) 3 produced an isotactic-rich polymer, whereas a syndiotactic polymer was obtained during the conventional radical polymerization without the Lewis acid. The tacticity of polymers often influences their physical properties and functions.…”

“…11 We also demonstrated that the chiral recognition ability of poly[(R) -1] was affected by the stereoregularity. 5 In this study, the radical polymerizations of four methacrylamides bearing optically -5), in the presence and absence of Lewis acids were carried out to synthesize the polymethacrylamides having different tacticities, and the relationship between the stereoregularity and the chiroptical properties of the polymers was discussed.…”

“…1,4,5 The conventional radical polymerizations of methacrylates 6 and methacrylamides, 4,5,7 except for those having bulky side chains, 8,9 generally produce a syndiotactic-rich polymer due to the steric repulsion between the side chains. On the other hand, Lewis acids interact with the monomers and the propagating chain-end to change the stereochemistry of the polymerization to isotactic-selective manner.…”