Synthesis of Photoresponsive Water-Dispersible Magnetite Nanoparticles using Arylazopyrazole Modified Polymers

In order to design new nanomaterials with improved functionalities, magnetite nanoparticles (MNP) modified with arylazopyrazole (AAP) molecular photoswitches are presented. Water-dispersibility is achieved by using poly(acrylic acid) (pAA) as a multidentate ligand, which is modified with AAP by amide coupling. The polymer ligand allows for the E-Z isomerization of the photoswitch, stabilizes the nanoparticles and provides pH responsiveness. Three different AAPs are synthesized and attached to pAA via amide coupling giving statistic co-polymers pAA-AAP. MNP are synthesized by co-precipitation and pAA-AAP is introduced as stabilizing agent in situ. Photoisomerization of pAA-AAP and pAA-AAP@MNP are investigated showing good photostationary states and cyclability. The nanoparticles can be assembled and dispersed reversibly in water by applying magnetic field and change in the pH value.