Self-assembly of a diblock copolymer on a patterned surface with low-energy electron beam.

A pattern was generated by 500 eV electron beam irradiation on benzaldimine monolayer through a grid and subsequent hydrolysis of nonirradiated regions. While we tried to assemble a block copolymer, polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP), on the pattern, we observed that the polarity difference between the two different regions was not right for discriminating the wetting behavior of two blocks of the polymer. Among various modifications of the retrieved amine, it was found that tribromoacetaldehyde was suitable for this end. Surprisingly, treatment of the aldehyde gave a surface preferring the polystyrene block to poly(4-vinylpyridine) block, while the irradiated section favored the latter block. As a result, island morphology was observed on the tribromoacetaldimine region and hole morphology on the irradiated region when the film thickness was 1.3Lo. Contact angle data were consistent with the observed symmetric wetting on the former region and the asymmetric one on the latter.

Modification of indium-tin oxide (ITO) glass with aziridine provides a surface of high amine density.

The surface of indium-tin oxide (ITO) substrates was successfully modified with aziridine. Modification of the surface was achieved through facile ring-opening, and hyperbranching polymerization of the ring-strained heterocycle initiated from the reactive group on the surface. Amine density of the aziridine-modified ITO measured with UV-vis spectrophotometry is 10 amines/nm2. Cyclic voltammetric analysis showed that the aziridine-modified electrode was less active for Ru(NH3)6(3+) in comparison with the pristine electrode, while no difference was observed for Fe(CN)6(4-). Electrochemical impedance spectroscopic experiments unveiled that the modified electrode was more efficient for electron transfer to the latter species than to the former.

Hyperbranching polymerization of aziridine on silica solid substrates leading to a surface of highly dense reactive amine groups.

Silica solid substrates such as fused silica, silicon wafers with a natural oxide layer, and glass were treated with aziridine to produce reactive primary amine groups on the top surface. We found that the hydroxyl group on the substrate was able to initiate the ring-opening polymerization of aziridine, resulting in highly branched poly(ethyleneimine) on the surface. In dichloromethane, the thickness of the organic film reached 25 A in 20 h and the absolute density of the primary amine group on the surface was 23 amines/nm(2). Atomic force microscopy shows an embossed morphology after the polymerization in dichloromethane, while use of toluene gives a rather smooth surface. The resulting organic layer shows high thermal and pH stability.