Light responsive thin films of micelles of PS-b-PVP complexed with diazophenol chromophore

Abstract

We have incorporated push-pull azobenzene units into diblock-copolymer micelles by supramolecular assembly. Specifically, we encapsulated a phenol-functionalized chromophore, DO13, within PS-b-P4VP micelles in toluene by means of H-bond interactions developed between DO13molecules and pyridine groups of P4VP block. The solutions were spincoated onto glass substrates to result in multi- or mono-layered thin films of micelles with P4VP(DO13) core and PS corona. We showed that the use of DO13 as building block of micellar aggregates allow us to manipulate the developed nanostructures. Spherical to cylindrical micellar transition was found when we increased the degree of chromophore complexation. Besides, it was found that the polymer concentration in the solution plays an important role in determining the micellar nanostructures. The chain extension and change in composition of the P4VP core in the presence of the chromophore, may be responsible for the structural changes observed in the micelles. The optical properties of the thin films have been investigated focusing on the effect of the micellar morphology over the photo-induced birefringence. The optical anisotropy increased with respect to the analogous homogenous system P4VP(DO13) indicating that the protective micelle environment can enhance the optical properties of the embedded chromophores significantly. Besides, we showed very interesting new results in which we have related changes in optical properties with the film morphology (spheres to cylinders). This can be exploited for producing optical devices having improved optoelectronic properties and stability.