title: Aggregation behavior of N-carboxyethylchitosan in aqueous solution: effects of pH, polymer concentration, and presence of a gemini surfactant.
abstract: A kind of biocompatible derivative of chitosan, N-carboxyethylchitosan (CECh) with a degree of substitution of 0.21 (DS 0.21) was synthesized by a Michael addition reaction. The aggregation behavior of CECh in aqueous solution under the effects of pH, polymer concentration, as well as a gemini surfactant, was investigated by turbidity, zeta potential, fluorescence spectroscopy, viscosity, and surface tension measurements. In the pH range of 3-11, the macroscopic phase separation of CECh from water occurs near the isoelectric point (IEP) due to the intense electrostatic attraction, and the intermolecular interaction at pH 4 is stronger than that at pH 10 over the whole CECh concentration region. The critical aggregation concentration (CAC) of CECh/12-n-12 (n=3, 6) in basic media is determined to be between 0.0010 and 0.0015 mmol/L, and the length of the surfactant spacer is found to play an important role in the interaction of 12-n-12 with CECh.
authors.affiliation: Key Laboratory for Advanced Materials and Department of Chemistry, East China University of Science and Technology, Shanghai 200237, China.
authors.forename: Baoliang
authors.initials: B
authors.lastname: Peng
authors.forename: Yongliang
authors.initials: Y
authors.lastname: Hao
authors.forename: Hongmei
authors.initials: H
authors.lastname: Kang
authors.forename: Xia
authors.initials: X
authors.lastname: Han
authors.forename: Changjun
authors.initials: C
authors.lastname: Peng
authors.forename: Honglai
authors.initials: H
authors.lastname: Liu
mesh_terms: D002117:Calcitriol / Q000031:analogs & derivatives* / Q000737:chemistry; D048271:Chitosan / Q000031:analogs & derivatives* / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D009391:Nephelometry and Turbidimetry; D011108:Polymers / Q000737:chemistry*; D012996:Solutions; D013050:Spectrometry, Fluorescence; D013500:Surface Tension; D013501:Surface-Active Agents / Q000737:chemistry*; D014867:Water / Q000737:chemistry*
chemical_list: C411462:1,25-dihydroxy-21-(3-hydroxy-3-methylbutyl)vitamin D(3); C495631:N-(2-carboxyethyl)chitosan; D011108:Polymers; D012996:Solutions; D013501:Surface-Active Agents; D014867:Water; D048271:Chitosan; D002117:Calcitriol