Hye Jeong Kim

High aspect ratio cylindrical microdomains oriented vertically on the substrate using block copolymer micelles and temperature-programmed solvent vapor annealing

We report a novel, yet simple, method for the preparation of high aspect ratio cylindrical microdomains oriented vertically on a substrate by using block copolymer micelles and temperature-programmed solvent vapor annealing. Multilayered spherical micelles were first prepared by spin-coating of polystyrene-block-poly(4-vinylpyridine) copolymer (PS-b-P4VP) in toluene solution on a silicon wafer. When temperature-programmed solvent vapor annealing was performed, the spherical micelle cores consisting of P4VP chains were transformed into vertically oriented cylindrical microdomains spanning the entire film thickness up to 550 nm corresponding to the aspect ratio of 15.2. Since nitrogen in the P4VP block could be easily coordinated with many metal precursors, we also fabricated a high density array of gold nanoparticle/polymer nanocomposite nanorods oriented vertically on the substrate.

Hydrostatic pressure effect on the phase transitions of a closed-loop type block copolymer by using 2D FTIR correlation spectroscopy.

The effect of hydrostatic pressure (P) on the phase transitions of polystyrene-block-poly(n-pentyl methacrylate) copolymer [PS-b-PnPMA] was investigated with FTIR spectroscopy at various temperatures. The experiments were performed by using a specially designed pressure cell optimized for low-pressure regime (<100 bar) with a higher resolution ( approximately 1 bar). The size of the closed loop consisting of both the lower disorder-to-order transition (LDOT) and the upper order-to-disorder transition (UODT) measured by FTIR spectroscopy becomes smaller with increasing P, consistent with results obtained from birefringence measurement. At lower temperatures with increasing P, the PS main chains are found to move before the PnPMA main chains. This is because the mobility of the PnPMA main chains is restricted due to the cluster formation of the alkyl side chain. At higher temperatures, the PnPMA block chains are more mobile than the PS block chains due to their larger specific volumes. The results indicate that the LDOT is mainly affected by a favorable directional interaction between PS and PnPMA blocks due to the cluster formation of the alkyl side chain, whereas the UODT depends on the combinatorial entropy.