Enhanced swelling using photothermal responsive surface‐immobilized microgels

• Published in: Journal of applied polymer science Vol. 138; no. 38
• Main Authors: Ou, Charly, Wang, Chang‐Sheng, Giasson, Suzanne
• Format: Journal Article
• Language: English
• Published: Hoboken, USA John Wiley & Sons, Inc 10.10.2021; Wiley Subscription Services, Inc
• Subjects: coatings; composites; Film thickness; gels; Gold; Materials science; Microbalances; Microgels; Nanoparticles; Phase transitions; Photon correlation spectroscopy; Polyisopropyl acrylamide; Polymers; Quartz crystals; stimuli‐responsive polymers; Surface charge; Swelling
• ISSN: 0021-8995; 1097-4628
• DOI: 10.1002/app.50973

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%. The swelling response of immobilized photothermal responsive microgels (PTRM) was quantitatively determined as a function of the temperature and under irradiation. The surface‐immobilized PTRM exhibited significant photothermal responsiveness. They showed a more important swelling compared to that in suspensions due to the high surface coverage.