title: Impact of volume transition on the net charge of poly-N-isopropyl acrylamide microgels.
abstract: We explore the electrostatic properties of poly-N-isopropyl acrylamide microgels in dilute, quasi-de-ionized dispersions and show that the apparent net charge of these thermosensitive microgels is an increasing function of their size, the size being conveniently varied by temperature. Our experimental results obtained in a combination of light scattering, conductivity, and mobility experiments are consistent with those obtained in Poisson-Boltzmann cell model calculations, effectively indicating that upon shrinking the number of counterions entrapped within the microgels increases. Remarkably, this behavior shows that the electrostatic energy per particle remains constant upon swelling or deswelling the microgel, resulting in a square root dependence of the net charge on the particle radius.
authors.affiliation: Department of Physics, University of Fribourg, CH-1700 Fribourg, Switzerland.
authors.forename: M
authors.initials: M
authors.lastname: Braibanti
authors.affiliation: Departamento de Ciencias Básicas, Universidad Autónoma Metropolitana-Azcapotzalco, Avenida San Pablo 180, 02200 Ciudad de México, Mexico.
authors.forename: C
authors.initials: C
authors.lastname: Haro-Pérez
authors.affiliation: Departamento de Física, Universidad de Jaén, Escuela Politécnica Superior de Linares, 23700 Linares, Spain.
authors.forename: M
authors.initials: M
authors.lastname: Quesada-Pérez
authors.affiliation: Departamento de Física, CINVESTAV-IPN, Avenida Instituto Politécnico Nacional 2508, 07360 Ciudad de México, Mexico.
authors.forename: L F
authors.initials: LF
authors.lastname: Rojas-Ochoa
authors.affiliation: Department of Physics, University of Fribourg, CH-1700 Fribourg, Switzerland.
authors.forename: V
authors.initials: V
authors.lastname: Trappe