posted on 2021-12-28, 18:04authored byXi Chen, Zhangyan Chen, Li Ma, Zhengran Yi
Multi-stimuli-responsive Janus composite
nanoparticles (JNPs) of
poly(N-isopropylacrylamide)–Fe3O4–poly(2-(dimethylamino)ethyl methacrylate)) (PNIPAM–Fe3O4–PDMEAMA) are synthesized by sequential
reversible addition–fragmentation chain-transfer grafting of
the polymer PNIPAM and atom-transfer radical polymerization grafting
of the polymer PDMEAMA from the corresponding sides of modified Fe3O4 nanoparticles of ∼10 nm size. The hydrophilic/amphiphilic/hydrophobic
reversible transition of the JNP can be triggered by pH and temperature
since the wettability of the two polymers on the opposite sides is
tunable accordingly. At a high pH value and a low surrounding temperature,
applying near-infrared irradiation will induce the amphiphilic/hydrophobic
transition owing to the photothermal effect of Fe3O4 NPs. The JNP can serve as a responsive solid emulsifier,
and the stability and microstructure of the emulsions can be easily
controlled by external stimuli such as the pH, temperature, and magnetic
field.