β-Cyclodextrin-derived alternating poly(glyco-triazole)s behave as amylose mimics

Abstract

Carbohydrate-derived polymers combine attractive features like abundant renewable resources, large stereochemical diversity and defined functionalization of the carbohydrates. Starting from β-cyclodextrin, a diazido heptasaccharide was regioselectively obtained in a few steps. It was used as a prepolymer for the A₂B₂ synthesis of alternating poly(glyco-triazole)s by copper assisted azido alkyne cycloaddition (CuAAC) with two dialkynes of different length and polarity, namely, 1,7-octadiyne and bispropargyl-polyetileneglycol-5. The resulting polymers were completely characterized by FTIR, NMR, MALDI-TOF-MS, SEC MALS, thermal analysis (TG and DSC), and SEM. The alternating insertion of the heptasaccharide and dialkyne in linear polymeric structures was confirmed by NMR and MALDI-TOF experiments. The water-soluble poly(glyco-triazole) containing PEG units had M_n 20,640 and M_w 39,650. The thermal properties (T_g = 27–42 °C) were close to those of amylose but were influenced by the linker. Therefore, these new poly(glyco-triazole)s could be considered as polysaccharide mimics and alternatives to modified native polysaccharides or brush polymers.