Preparation and UCST-type phase behavior of glycopolypeptides in alcoholic solvents

Abstract

Glycopolypeptides with different contents of tetra-O-acetyl-D-(+)-mannopyranoside and tetra-O-hydroxyl-D-(+)-mannopyranoside pendants were prepared via copper-mediated [2 + 3] alkyne-azide 1,3-dipolar cycloaddition. Glycopolypeptides with high contents of tetra-O-acetyl-D-(+)-mannopyranoside (x ≥ 44%) exhibited a reversible UCST-type phase behavior in both methanol and ethanol. FTIR analysis revealed that the mechanism of the UCST-type phase behavior originated from the hydrophobic interaction and H-bonding between the polymers and the H-bonding between the polymer and solvent. Variable-temperature UV-vis analysis revealed that the UCST-type transition temperatures (T_pts) of the resulting glycopolypeptides increased as the polymer concentration or main-chain length increased. Incorporation of proton donating groups (i.e., tetra-O-hydroxyl-D-(+)-mannopyranoside) or increasing the number of carbons of aliphatic alcohols led a decrease of maximal concentration and increase of T_pt.