Enhanced swelling using photothermal responsive surface‐immobilized microgels

Abstract

Unprecedented quantitative assessment of the swelling behavior of surface‐immobilized photothermal responsive microgels (PTRM) is reported. The PTRM were prepared by incorporating plasmonic gold nanoparticles (AuNPs) in thermo‐responsive cationic microgels based on poly(N‐isopropylacrylamide) (BM). The stimuli‐responsive behavior of the microgels was investigated in aqueous suspensions using Dynamic Light Scattering (DLS) and on surfaces using a Quartz Crystal Microbalance with Dissipation (QCM‐D) as well as with the Surface Forces Apparatus (SFA). Both the BM and PTRM in aqueous suspensions underwent a similar temperature‐induced volume phase transition at around 35°C. The complexation of AuNPs with the BM led to a decrease in the surface charge allowing to increase the surface grafting density. This favored a unidirectional upward swelling of the surface immobilized PTRM. The study reports significant photo‐triggered swelling responses on surface with decreases in film thickness up to 82%.