Effect of Interactions Between Anionic Vesicles and a Cationic Terpolymer in Concentrated Solution Regime: Morphology and Size Changes of the Vesicular Particles

Interactions between polyelectrolytes and oppositely charged vesicular particles have many possible applications in drug delivery or gene therapy. Formation of vesicular structures by 2-(propylcarbamoyl) terephthalic acid heptaisobutyl POSS (POSS DCA) in a solvent mixture comprising acetone, ethanol, and 1-propanol has been already proved by the same authors. Particle size and morphology of POSS DCA vesicular particles were investigated as a function of ultrasonication (sonicated vs. non-sonicated) and concentration (23 or 34 mM) and correlated to the interactions occurring between the vesicles and a cationic random terpolymer. Concentrated solutions (56% w/w) of the terpolymer i.e., poly(dimethylaminoethyl methacrylate-co-methyl methacrylate-co-butyl methacrylate) were prepared in the above solvent mixture containing POSS DCA particles. Morphological changes of the particles in the concentrated solutions were studied by atomic force microscopy (AFM) and conformity of the AFM findings with rheological results was investigated. Interactions between the terpolymer and spherical vesicular particles (mean diameter c.a. 4.5 μm in non-sonicated state; C=23 or 34 mM) led to disappearance of the particles and formation of smaller elliptical particles (mean diameter ranging 70 to 700 nm), respectively. At 34 mM POSS DCA concentration, the interactions between the terpolymer chains and sonicated vesicular particles (mean diameter c.a., 4.5 μm with approx. 8 μm length) led to formation of irregular, aggregated, lamellar structures. Some of these findings were confirmed by the rheological results. The results were interpreted considering self-assembly of the terpolymer chains, vesicle shell peeling by the polyelectrolyte chains, and diffusion of the chains into the shells.