title: Insights into the interactions among Surfactin, betaines, and PAM: surface tension, small-angle neutron scattering, and small-angle X-ray scattering study.
abstract: The interactions among neutral polymer polyacrylamide (PAM) and the biosurfactant Surfactin and four betaines, N-dodecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (SDDAB), N-tetradecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (STDAB), N-hexadecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (SHDAB), and N-dodecyl-N,N-dimethyl-2-ammonio-acetate (C12BE), in phosphate buffer solution (PBS) have been studied by surface tension measurements, small-angle neutron scattering (SANS), small-angle X-ray scattering (SAXS), and rheological experiments. It has been confirmed that the length of alkyl chain is a key parameter of interaction between betaines and PAM. Differences in scattering contrast between X-ray and neutrons for surfactants and PAM molecules provide the opportunity to separately follow the changes of structure of PAM and surfactant aggregates. At concentrations of betaines higher than CMC (critical micelle concentration) and C2 (CMC of surfactant with the presence of polymer), spherical micelles are formed in betaines and betaines/PAM solutions. Transition from spherical to rod-like aggregates (micelles) has been observed in solutions of Surfactin and Surfactin/SDDAB (αSurfactin = 0.67 (molar fraction)) with addition of 0.8 wt % of PAM. The conformation change of PAM molecules only can be observed for Surfactin/SDDAB/PAM system. Viscosity values follow the structural changes suggested from scattering measurements i.e., gradually increases for mixtures PAM → Surfactin/PAM → Surfactin/SDDAB/PAM in PBS.
authors.affiliation: Shanghai Key Laboratory of Functional Materials Chemistry and State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology , Shanghai 200237, People's Republic of China.
authors.forename: Jingwen
authors.initials: J
authors.lastname: Xiao
authors.forename: Fang
authors.initials: F
authors.lastname: Liu
authors.forename: Vasil M
authors.initials: VM
authors.lastname: Garamus
authors.forename: László
authors.initials: L
authors.lastname: Almásy
authors.forename: Ulrich A
authors.initials: UA
authors.lastname: Handge
authors.forename: Regine
authors.initials: R
authors.lastname: Willumeit
authors.forename: Bozhong
authors.initials: B
authors.lastname: Mu
authors.forename: Aihua
authors.initials: A
authors.lastname: Zou
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry*; D001622:Betaine / Q000737:chemistry*; D033363:Neutron Diffraction; D053838:Scattering, Small Angle; D013500:Surface Tension; D013501:Surface-Active Agents / Q000737:chemistry*; D014961:X-Ray Diffraction; D000099166:Polyacrylamides
chemical_list: D000180:Acrylic Resins; D001622:Betaine; D013501:Surface-Active Agents; D000099166:Polyacrylamides