Thermo-responsive behaviors and bioactivities of hydroxybutyl chitosans prepared in alkali/urea aqueous solutions

A series of hydroxybutyl chitosans (HBCSs) with a degree of substitution (DS) ranging from 0.38 to 1.54 were homogeneously synthesized in KOH/LiOH/urea aqueous solutions under ambient conditions. The structure and solution properties of HBCSs were characterized by FT-IR, NMR, SEC-LLS, UV–vis, rheological and DLS measurements. The amino groups at C2 and hydroxyl groups at C3 and C6 participated in the reaction, although substitution mainly...