Self-assembly of a novel organometallic-inorganic block copolymer in solution and the solid state:: Nonintrusive observation of novel wormlike poly(ferrocenyldimethylsilane)-b-poly(dimethylsiloxane) micelles

The novel organometallic-inorganic diblock copolymer, poly(ferrocenyldimethylsilane)-b-poly(dimethylsiloxane) (PFS-b-PDMS) (block ratio = 1.0:6.0) (M-n = 35 100 g/mol with a narrow molecular weight distribution M-w/M-n = 1.10 based upon gel permeation chromatography in THF using polystyrene standards) forms long rodlike micelles in hexane solution. After the solvent was evaporated, transmission electron microscopy (TEM) and atomic force microscopy (AFM) showed that individual cylindrical micellar structures form with the iron-rich, organometallic PFS core encased in a sheath (corona) of PDMS. The block copolymer forms hexagonally packed cylinders in the bulk, and exposure to warm hexane causes the cylinders to disperse in the solvent. Both static and dynamic light scattering (SLS and DLS) were used to establish that the micelles are flexible rods which are stable in hexane even at 80 degrees C. The as-prepared sample possessed an aggregation number of ca. 2000 polymer molecules. Ultrasonication (60 W) in hexane led to the generation of short cylinders with an aggregation number of ca. 700. Since PFS can be oxidized to a semiconductive state and PDMS is an insulator, these rodlike micellar structures have the potential to function as nanoscale self-insulated wires.