We report the synthesis and characterization of three novel azobenzene-containing miktoarm star polymers AB3 (Mn = 14 800, ĐM = 1.22, Mn = 17 400, ĐM = 1.10 and Mn = 26 200, ĐM = 1.12) as well as their self-assembly properties in water. The three polymers are composed of an azopolymer and three identical arms of poly(N,N-diethylacrylamide) (PDEAA), featuring thermo-responsive properties. By carefully selecting the polymerization degree of PDEAA, and consequently the hydrophobic/hydrophilic ratio, a specific miktoarm polymer has been identified that forms stable micelles in water as is clearly revealed by Transmission Electron Microscopy (TEM). In addition, the thermo- and photo-responsive properties of the polymeric micelles in water were investigated. Encapsulation of Nile Red was probed via fluorescence spectroscopy as well as its release from the loaded probes triggered by UV irradiation, which causes a trans-to-cis isomerisation of the azobenzene moieties.

The study was supported by the MINECO, Spain, under the project MAT2011-27978-C02-01, Fondo Europeo de Desarrollo Regional (FEDER), Gobierno de Aragon and Fondo Social Europeo. E. Blasco acknowledges the CSIC JAE-Pre contract funding her PhD. The authors acknowledge the Servicio de Microscopía Electrónica-Universidad de Zaragoza for the TEM experiments. The authors additionally acknowledge the use of the Servicio General de Apoyo a la Investigación-SAI, Universidad de Zaragoza. C.B.-K. acknowledges funding from the Karlsruhe Institute of Technology (KIT) in the context of the Helmholtz BioInterfaces and STN research programs, the German Research Council (DFG) as well as the ministry of science and arts of the state of Baden-Württemberg.

Peer reviewed