Dependency of Particle Sizes and Colloidal Stability of Polyelectrolyte Complex Dispersions
on Polyanion Structure and Preparation Mode Investigated by Dynamic Light Scattering
and Atomic Force Microscopy†
posted on 2007-07-26, 00:00authored byMarcela Mihai, Ecaterina Stela Dragan, Simona Schwarz, Andreas Janke
Polyelectrolyte complex (PEC) dispersions were prepared by controlled mixing of three random copolymers
of sodium 2-acrylamido-2-methylpropanesulfonate (AMPS) with either t-butyl acrylamide (TBA) [P(AMPS54-co-TBA46) and P(AMPS37-co-TBA63)] or methyl methacrylate (MM) [P(AMPS52-co-MM48)] with an ionene-type polycation, containing 95 mol % N,N-dimethyl-2-hydroxypropyleneammonium chloride repeat units
(PCA5), with their structural characteristics being deeply investigated by dynamic light scattering (DLS) and
atomic force microscopy (AFM). Shape, size, and polydispersity of the PEC dispersions were directly observed
by AFM as a function of polyanion structure, the ratio between charges, n-/n+, and the titrant addition rate
(TAR). The particle sizes increased and the colloidal stability decreased with the increase of the nonionic
comonomer content and with the decrease of TAR. It was demonstrated that the medium particle sizes of the
complex nanoparticles adsorbed on silicon wafers measured by AFM, in the dry state, were close but always
lower than those measured by DLS, both before and after the complex stoichiometry.