Effect of added homopolymer on structures of thin films of PS-b-PDMS/PS mixture under solvent vapor annealing

Self assembly of poly(styrene-b-dimethylsiloxane) (PS-b-PDMS) followed by reactive ion etching technique is a promising method for fabricating periodical silica nanopatterns and can be applicable for device fabrication on nanoscale. We demonstrated a technologically useful way to control the inorganic silica nanostructures in thin films by directly mixing asymmetric (PS-b-PDMS) diblock copolymer with homopolymers of majority component, polystyrene (PS) under solvent vapor annealing followed by UV/O3 treatment. The effects of molecular weight and volume fraction of added homopolymer (PS) on morphology and size of the nanostructure of blends have been carefully investigated by atomic force microscopy. Different morphology transitions observed on the ordering film surface by atomic force microscopy (AFM) are associated with kinetics of phase evolution with respect to homo-PS with different molecular weight. The periodic spacings and dimensions of the microdomains were readily tuned at the same time, just by adjusting the molecular weight and volume fraction of the blended homopolymer.

Research highlights▶ The long-ordering of inorganic silica result from self assembly of PS-b-PDMS/PS blends followed by UV/O3 treatment. ▶ Addition of homo-PS leads to phase transitions. ▶ Molecular weight and volumer fracture of blended homo-PS tune the spacing of inorganic silica.