(533b) Polymer Nanoclusters Preparation through Aggregation and Breakage Processes

Polymer nanoclusters (NCs) obtained by aggregation of primary polymer nanoparticles (NPs) find application in different research and industrial fields ranging from food and cosmetic to pharmaceutical products. Even if they present large interest, in the literature understanding of the physical processes involved in their production is still lacking. NPs size and chemical composition together with NCs structure and size are fundamental aspects which affect the final product features and application. The aim of the present work is to investigate the production of NCs on the base of selected key parameters, such as NPs size, surface charge type, charge density, stabilizer nature and system fluid dynamics. Experimentally, primary NPs of PMMA, with different surface charge density, stabilized by SDS and with particle size ranging from 15 to 40 nm, were produced through starved emulsion polymerization process. To investigate different stabilizers, SDS removal by ion-exchange resins was applied as intermediate step during the NCs production. The NPs were then aggregated in DLCA regime producing large clusters of several microns in diameter by addiction of an electrolyte solution. Surfactant was then added to the cluster dispersion and controlled breakage was used to reduce size of clusters down to nanometer scale. To obtain well define conditions during breakage, characterized by CFD, suspension was pumped through contracting nozzle. Characterization of NCs size and structure was carried out by light scattering analysis and TEM. Different surfactants, such as Tween 80, PVA and pluronics, and different concentrations, ranging from 0.5 to 50 surfactant polymer ratio, were investigated. Results show a clear dependence of NCs size upon the selected operating conditions. In particular, the cluster size becomes independent upon surfactant/polymer ratio larger than 10 while it shows a strong dependency upon applied hydrodynamic stress. The experimental findings are used to construct a reliable tool for tailor made production of NCs for specific applications.