Preparation and thermoresponsive properties of UCST-type glycopolypeptide bearing mannose pendants and 3-methyl-1,2,3-triazolium linkages in ethanol or ethanol/water solvent mixtures

Abstract

A series of glycopolypeptides with constant main-chain lengths and bearing various mannose pendants and 3-methyl-1,2,3-triazolium linkages were synthesized by N-alkylation, ion-exchange reaction, and subsequent deprotection. 1H NMR and FTIR analysis verified their molecular structures. Their solubility and thermoresponsive properties were collectively affected by polymer structure, polymer concentration, and the nature of solvent. Glycopolypeptides bearing tetra-O-acetyl-d-(+)-mannopyranoside and 3-methyl-1,2,3-triazolium chloride linkages showed a reversible upper critical solution temperature (UCST)-type phase behavior in ethanol (EtOH) with a solution phase transition temperature (T pt) in the range of 39.7–47.4 °C depending on polymer concentration. Glycopolypeptides bearing tetra-O-acetyl-d-(+)-mannopyranoside and 3-methyl-1,2,3-triazolium iodide or 3-methyl-1,2,3-triazolium tetrafluoroborate linkages showed a reversible UCST-type phase behavior in EtOH/H2O solvent mixtures. The T pt can be adjusted in the range of about 10–50 °C by polymer concentration or the weight percentage of ethanol (f w). It increased as the polymer concentration or f w increased.