Improving Colloidal Stability and Response Performances of Using Looped thermal-responsive Brush

Abstract

Looped polymer brushes lacking chain terminals exhibited unique topological structures and associated properties. The looped polymer brushes in solution had been extensively studied, although the topology and corresponding performances of the thermal-responsive polymer upon grafting onto nanoparticle surfaces were hardly reported. In this work, the gold nanoparticles (AuNPs) were modified using poly(N-isopropyl acrylamide) (PNIPAAm) terminated with one thiol and two thiol groups to prepare the linear and looped PNIPAAm brush-coated AuNPs, respectively. The effect of the topology of PNIPAAm brushes on thermal-responsive behavior, colloidal stability and release performances was evaluated in detail. Compared to the linear counterparts, the looped polymer exhibits relatively higher colloidal stability and rapid thermal-responsive behavior during heating-cooling temperature cycling. This resulted in a more pronounced release of dye molecules triggered by looped one by temperature change, even if the release is first saturated at 25 oC and then triggered twice by raising the temperature to 45 oC. In contrast, the linear polymer brushes did not show significant triggering behavior due to chain entanglement. This work demonstrated how the polymer brush topology affected thermal-responsive nanoparticles' stability and temperature-responsive behavior, which may provide new opportunities for surface modification of looped polymer brushes with temperature-sensitive properties.