pH-Sensitive Adsorption Behavior of Polymer Particles at the Air–Water Interface

Abstract

pH-Sensitive adsorption of polymer particles bearing poly[2-(dimethylamino)ethyl methacrylate] hairs at the air-water interface was investigated using a surface tensiometer, a Langmuir-Blodgett trough, and an X-ray reflectometer. We clarified that the particles are adsorbed at the interface at basic pH; by contrast, at acidic pH, only a small number of particles are adsorbed, whereas the majority are dispersed in the water phase. X-ray reflectometry analysis revealed that a particle monolayer was formed at the air-water interface, which was packed densely under increasing surface pressure, as determined by the electron density profile change. The contact angles of the particles at the air-water interface were estimated to be 29° and 34° at pH 3 and 10, respectively, by direct visualization of the air-water interface position of the particles using a polycyanoacrylate trapping method.

Poly(dimethylaminoethyl methacrylate)‐b‐poly(hydroxypropyl methacrylate) copolymers: Synthesis and pH/thermo‐responsive behavior in aqueous solutions

“…The synthesized PDMAEMA ‐b‐ PHPMA copolymers consist of a hydrophilic PDMAEMA block and a weakly hydrophobic and water insoluble PHPMA block. At pH 3, PDMAEMA is fully protonated and molecularly soluble in aqueous media, thus it is expected to show no thermoresponsiveness . At pH 7 and pH 10, PDMAEMA is partially protonated and fully deprotonated respectively and thus presents a temperature transition in both cases .…”

“…At pH 3, PDMAEMA is fully protonated and molecularly soluble in aqueous media, thus it is expected to show no thermoresponsiveness . At pH 7 and pH 10, PDMAEMA is partially protonated and fully deprotonated respectively and thus presents a temperature transition in both cases . Also, at pH 10 the deprotonated PDMAEMA amine groups have reduced solubility in aqueous solution and thus there is the need of another soluble/hydrophilic block to stabilize the system, otherwise the block copolymers are precipitated .…”

“…The surface charge of the diblock copolymer aggregates was studied through electrophoretic light scattering (ELS) measurements and the results are shown in Table . The amine and quaternized amine functional copolymer aggregates show positive zeta potential ( ζ p) values, due to the partially protonated PDMAEMA blocks at pH 7 aqueous solutions …”

“…Poly(dimethylaminoethyl methacrylate) (PDMAEMA) is a hydrophilic, pH and temperature responsive polymer . When in aqueous solutions of pH < 7 it is fully charged (protonated) and thus it does not exhibit any temperature responsiveness.…”

“…When in aqueous solutions of pH < 7 it is fully charged (protonated) and thus it does not exhibit any temperature responsiveness. When at pH 7 or higher, it is partially charged (protonated) or uncharged and thus it exhibits a temperature response, which depends on its molecular weight . PDMAEMA exhibits biocompatibility and is used for biomedical applications, such as gene transfer and drug delivery .…”