Theoretical and Experimental Design of Heavy Metal-Mopping Magnetic Nanoparticles.

Elia Roma,Pietro Corsi,Nikolaus Simon Leitner,Barbara Capone,Max Willinger,Ronald Zirbs,Erik Reimhult,Tecla Gasperi

doi:10.1021/acsami.0c17759

Abstract

Herein, we show a comprehensive experimental, theoretical, and computational study aimed at designing macromolecules able to adsorb a cargo at the nanoscale. Specifically, we focus on the adsorption properties of star diblock copolymers, i.e., macromolecules made by a number f of H-T diblock copolymer arms tethered on a central core; the H monomeric heads, which are closer to the tethering point, are attractive toward a specific target, while the T monomeric tails are neutral to the cargo. Experimentally, we exploited the adaptability of poly(2-oxazoline)s (POxs) to realize block copolymer-coated nanoparticles with a proper functionalization able to interact with heavy metals and show or exhibit a thermoresponsive behavior in aqueous solution. We here present the synthesis and analysis of the properties of a high molecular mass block copolymer featured by (i) a polar side chain, capable of exploiting electrostatic and hydrophilic interaction with a predetermined cargo, and (ii) a thermoresponsive scaffold, able to change the interaction with the media by tuning the temperature. Afterward, the obtained polymers were grafted onto iron oxide nanoparticles and the thermoresponsive properties were investigated. Through isothermal titration calorimetry, we then analyzed the adsorption properties of the synthesized superparamagnetic nanoparticles for heavy metal ions in aqueous solution. Additionally, we use a combination of scaling theories and simulations to link equilibrium properties of the system to a prediction of the loading properties as a function of size ratio and effective interactions between the considered species. The comparison between experimental results on adsorption and theoretical prediction validates the whole design process.

Highlights

In recent years, synthesis and investigations of polymer properties have focused on the design of macromolecules, able to perform predetermined tasks and sensitive to external stimuli
We successfully synthesized a versatile block copolymer composed by (i) an outer thermal responsive tail-block in aqueous solution to control the colloidal stability and (ii) an inner head-block made of monomers with an ionizable side chain that could be used to chelate predetermined compounds in solution, similar to the ethylenediaminetetraacetic acid (EDTA) behavior
The thermoresponsivity of the outer shell of the superparamagnetic nanoparticles (SPMNPs) might allow for a thermal control of their average; this might lead to the possibility of a thermal tuning of the aggregation of the nanoparticles in solution

Summary

Introduction

Synthesis and investigations of polymer properties have focused on the design of macromolecules, able to perform predetermined tasks and sensitive to external stimuli. PiPrOx exhibits a lower critical solution temperature (LCST) in water around 38 °C, which is just above body temperature,[30] and higher than that of PNIPAAm (LCST = 32 °C) This makes PiPrOx a good candidate for the design of thermoresponsive polyoxazoline-based polymer that can undergo a phase transition in pure water, i.e., from a dispersible state at low temperature to a collapse state at different conditions.[31−34] This work focuses on the design, synthesis, and characterization of a new macromolecule that has been developed to perform a pre-determined action in aqueous solution. We compare theoretical predictions to experimental realizations and characterizations with the aim of highlighting the main features that render a spherical core− shell polymeric nanoparticle an efficient adsorbing system

Methods

Results

Conclusion