Synthesis and self-assembly of crystalline-b-coil hybrid block copolyphosphazenes

Our group has been recently studying the self-assembly of polyphosphazene block copolymers. Such versatile materials allowed us the synthesis of block copolymers having a chosen property located in the core-forming block and,... [ view full abstract ]

Our group has been recently studying the self-assembly of polyphosphazene block copolymers. Such versatile materials allowed us the synthesis of block copolymers having a chosen property located in the core-forming block and, therefore, assess the influence of this property over the self-assembly in solution and in thin films.

Thus, we prepared polyphosphazene-based block copolymers having chiral and functional blocks able to direct the self-assembly to pores, helix, or nanostructures functionalised with gold nanoparticles (AuNPs). In this communication we report the formation of two complex nanostructures; toroidal micelles and bicontinuous nanospheres, by the self-assembly of a single and structurally simple crystalline-b-coil diblock copolymer poly[bis(trifluoroethoxy)phosphazene]-b-poly(styrene), PTFEP-b-PS, in one solvent (THF) and without additives. The nature of these nanostructures in solution was confirmed by DLS and cryo-TEM experiments. The two morphologies are related by means of a new type of reversible morphological evolution, bicontinuous-to-toroidal, triggered by changes in the polymer concentration. WAXS experiments showed that the crystallinity degree of the PTFEP chains located at the core of the toroids was higher than that in the bicontinuous nanospheres, evidencing that the final morphology of the aggregates is mostly determined by the ordering of the PTFEP core-forming blocks.