Characterization of polymer-brush-type polysaccharide β-ketoesters

Polyvinyl alcohol (PVA) and four glucans, cellulose, curdlan, amylase, and pullulan, were dissolved in 8% lithium chloride/1,3-dimethyl-2-imidazolodinone, and reacted with ketene dimers with long alkyl or alkenyl chains under homogeneous conditions. The corresponding polysaccharide beta-ketoesters with degrees of substitution (DS) of 2.1-2.9 and the PVA beta-ketoester with DS 0.9 were prepared in the yields of 80-90%. Solution-state H-1- and C-13-NMR spectra of the polysaccharide and PVA beta-ketoesters revealed that the polymer chains behaved like solid even in solutions. However, size-exclusion chromatographic analysis showed that the polysaccharide and PVA beta-ketoesters prepared had random-coil conformations in tetrahydrofuran, which could not explain the anomalous NMR patterns. The specific chemical structures of the substituents having long and branched alkyl or alkenyl chains may have brought about such specific solution-state NMR patterns, irrespective of the chemical structures of the polymer backbones. (C) 2008 Wiley Periodicals, Inc.