(734f) Asymmetric Functionalization of Shape-Anisotropic Polymer Nanoparticles

In the research in the field of nanoparticle in the last years, much attention has been devoted to the synthesis of anisotropic nanoparticles, also called Janus Nanoparticles. Anisotropicity may be provided in different ways, usually either in terms of non-homogeneous surface functionalization, or as compartmentalized internal structure. These special features render the nanoparticles much more interesting than their isotropic counterparts, especially regarding their self-assembling properties.

In this work, a two-step emulsion based polymerization has been applied to synthesize shape-anisotropic dumbbell nanoparticles, which size and morphology can be tuned by changing the process parameters. Narrowly distributed surfactant-free polystyrene nanoparticles are used as seeds. They are coated with a random copolymer of styrene and 3-trimethyloxyxilyl propyl acrylate (MPS), bringing silane groups on the surface of the seeds. The particles are then swollen with a monomer solution before a second polymerization. Due to the hydrophilic shell on the surface of the nanoparticles, the newly formed polymer is bulging out of the seeds, giving birth to dumbbell-like nanoparticles. The resulting nanoparticles are not only anisotropic in shape, but also in term of surface chemistry. The first bulb is bearing silane groups coming from the MPS, while the second is only made of polystyrene. This specific feature can be used for further asymmetric functionalize the dumbbells. Silane chemistry can be applied, which will result in the functionalization of the first hemisphere only. Superparamagnetic iron oxide nanoparticles (SPIONS) can be coated by surfactant having silane group, offering the possibility to attach SPIONS only to one bulge. The same approach has been used for platinum nanocrystals, leading to particles that can be used as Janus nanomotors in H2O2 solution.