Thermoresponsive Gold Polymer Nanohybrids with a Tunable Cross-Linked MEO2MA Polymer Shell

• Published in: Particle & particle systems characterization Vol. 31; no. 11; pp. 1183 - 1191
• Main Authors: Lapresta-Fernández, Alejandro, García-García, José Manuel, París, Rodrigo, Huertas-Roa, Rafael, Salinas-Castillo, Alfonso, de la Llana, Sabrina Anderson, Huertas-Pérez, José Fernando, Guarrotxena, Nekane, Capitán-Vallvey, Luis Fermín, Quijada-Garrido, Isabel
• Format: Journal Article
• Language: English
• Published: Weinheim Blackwell Publishing Ltd 01.11.2014; Wiley Subscription Services, Inc
• Subjects: core-shell materials; gold nanoparticles; nanohybrid colloids; thermoresponsive materials
• ISSN: 0934-0866; 1521-4117
• DOI: 10.1002/ppsc.201400078

Gold nanoparticles (AuNPs) are functionalized with a thermoresponsive polymer shell of a cross‐linked poly(2‐(2‐methoxyethoxy)ethyl methacrylate) (P(MEO2MA)). To provide a covalent attachment of the polymer to the NP surface, AuNPs are first modified using butanoic acid to develop the encapsulation with the biocompatible thermoresponsive polymer formed by free‐radical precipitation polymerization. Both the MEO2MA concentration and the shell cross‐linking density can be varied and, in turn, the thickness and the shells' free volume can be fine‐tuned. By downscaling the size of the polymeric shell, the lower critical solution temperature (LCST) is decreased. The LCST in the nanohybrids changes from 19.1 to 25.6 °C when increasing the MEO2MA content; it reaches almost 26 °C for P(MEO2MA) (bulk). The maximum decrease in the volume of the nanohybrids is around 40%, resulting in a modification of the light scattering properties of the system and causing a change in the turbidity of the gel network. The sizes of the nanohybrids are characterized using both transmission electron microscopy and dynamic light scattering measurements. Optical properties of the colloidal systems are determined using the derived count rate measurements as an alternative to absorbance or transmittance measurements, confirming the colloidal stability of the nanohybrid systems. Multifunctional thermoresponsive hybrid nanosystems consisting of a gold nanoparticle core and a poly(2‐(2‐methoxyethoxy)ethyl methacrylate) (P(MEO2MA))‐based hydrogel shell are synthesized. Control over the shell thickness, size, and the swelling/shrinking capability of the shell can be fine‐tuned by changing MEO2MA/cross‐linker/gold nanoparticle ratio. This results in thermally modulated optical properties of the nanohybrid systems.