Aggregation kinetics of stimulus-responsive polymer-coated gold nanoparticles driven by Hofmeister effects

Stability of engineered nanomaterials within natural aquatic systems is generally difficult to predict due to multiple roles that background electrolytes may play in these suspensions. Here we utilize core shell nanoparticles based on random copolymers of di(ethylene glycol) methyl ether methacrylate (x = MEO(2)MA) and oligo(ethylene glycol) methyl ether methacrylate (y = OEGMA) to investigate specific ion effects on colloidal stability. Aggregation kinetics (k(11)) of ALRP(MEO(2)MA(x)-co-OEGMA(y)) NPs were measured for KG, NaCl, SrCl2, and MgCl2 at various concentrations by means of time-resolved dynamic light scattering (TR-DLS). It was found that the smallest concentration of K+ and the greatest concentration of Mg2+ were required to increase the aggregation rate Specifically, we demonstrate k(11) scales not only as a result of ionic strength, but also in some cases in a direction opposite to that expected by the Schultz-Hardy rule. For these systems, aggregation kinetics can be better predicted by ion characterization within the well-established Hofmeister series. (C) 2016 Elsevier B.V. All rights reserved.