Effects of molecular weight, degree of acetylation and ionic strength on surface tension of chitosan in dilute solution

The effects of molecular weight, degree of acetylation and ionic strength on surface tension of chitosan in dilute aqueous solution were studied systematically using the maximum bubble pressure (MBP) technique. The results show that the surface tension decreases slightly with increasing chitosan concentration in the high dilution (<0.01010−2 kg l−1), above the critical aggregation concentration (0.01×10−2 kg l−1), the surface tension increases apparently for the high molecular weight chitosans or in the lower ionic strength solutions; whereas the degree of acetylation has little effect on the surface tension of chitosans especially in hydrochloric acid solution. It is considered that the changes of surface tension are attributed to the molecules conformation transition in dilute solution, resulting in a variation of intra/inter molecular interactions, i.e. hydrogen bonding, hydrophobic interaction and electrostatic interaction.