Small Angle X-Ray Scattering studies in steric stabilized pH responsive polystyrene colloidal particles

PERUZZO, P.J.; ANBINDER, P.S.; PLIVELIC, T.S.; AMALVY, J.I.

Campinas

Congreso; 20ª Reunión Anual de Usuarios LNLS - RAU 2010; 2010

LNLS

Steric stabilized pH-responsive colloids particles are very useful in several applications like drug delivery. Small-angle X-ray scattering (SAXS) has been reported to be an excellent tool for the study of these composite latexes since the electron densities of the polymers commonly used for the synthesis of such particles di®er markedly. Since the excess electron density of polystyrene latex particles in water is very small, the scattering from adsorbed layer of stabilizer, dominates the measured intensity in this particular systems. In this work we report the study of core shell polystyrene colloidal particles sterically stabilized by a pH-sensitive copolymer formed by methyl methacrylate and N,N-diethyl ethylmethacrylate. Two different molecular weight of the stabilizer copolymer were used changing in that way the thickness of the shell. SAXS measurements on samples were performed at the SAXS2 beam line at the LNLS (Campinas, Brazil) using a monochromatic beam of wavelength 1.488 ºA an exposure time of 600 sec, and a sample detector distance of 1909.87 mm.The SAXS data allow determining the thickness of the layer by modeling the core-shell morphology. The thickness of the shell modi¯es after changing the medium pH by addition of acid. The change in shell thickness is also determined by SAXS data.