title: pH dependent elasticity of polystyrene-block-poly(acrylic acid) vesicle shell membranes by atomic force microscopy.
abstract: We assess the elastic properties of PS-b-PAA vesicle membranes under different pH values by AFM force measurements. We find that based on the shell deformation theory, the values of the estimated apparent Young's modulus of the vesicle membranes decrease as the pH of the solution increases. The onset of the decrease of E coincides with the surface pK(a)  determined from ζ-potential measurements. This decrease of E at higher pH is attributed to electrostatic repulsion between the deprotonated PAA chains resulting in the thinning of the vesicle membrane.
authors: Department of Materials Science and Technology of Polymers, University of Twente, MESA+ Institute for Nanotechnology, P.O. Box 217, 7500 AE Enschede, The Netherlands.
authors: Qi
authors: Q
authors: Chen
authors: G Julius
authors: GJ
authors: Vancso
mesh_terms: D000179:Acrylates / Q000737:chemistry*; D004548:Elasticity; D006863:Hydrogen-Ion Concentration; D018625:Microscopy, Atomic Force; D011137:Polystyrenes / Q000737:chemistry*; D055672:Static Electricity; D013499:Surface Properties
chemical_list: D000179:Acrylates; D011137:Polystyrenes; C509855:poly(styrene-b-acrylic acid)