Correlation of micellar aggregation - complexation regimes to discern stability of micellar structure and nano-encapsulation

Abstract

Hypothesis: The physico-chemical mechanisms associated reverse micelle based encapsulation processes deserve investigation owing to the direct correlation between stability of micellar structure and nano encapsulation. The presence of core nanoparticles is expected to influence the stability of micellar structure when the concentrations of surfactant and particle concentration are varied. Hence, it should be possible to define the micellar aggregation - complexation regimes and systematic measurements have robust implications for nano encapsulation.

Experiments: Reverse micelle systems stabilized by non-ionic surfactant are formulated with the presence of core nanoparticles. Micellar aggregation and complexation processes are analyzed in two different oil phase (n-hexane and n-butanol). The regimes are probed by measuring average hydrodynamic diameter of reverse micelle, optical transmittance and specific conductivity. Shell encapsulation experiments are performed in aggregation and complexation regimes.

Findings: When the concentration of surfactant increases, reverse micelle size increases (to dia ∼ 200 nm). This is a reversal of the otherwise reported trend wherein the core is absent. Breakdown of stable reverse micellar structure obstructs shell coating and this is a first attempt to analyze micellar aggregation - complexation regimes with the presence of core. Reverse micelle breakage or complexation is to be completely avoided to achieve core@shell nanoparticles.

Keywords: Aggregation – complexation; Core@shell; Nano encapsulation; Reverse micelle; Surfactant.