Monolayers of a predominantly hydrophobic poly(styrene)-b-poly(ethylene oxide) copolymer (7% PEO by mass) were transferred to a silicon substrate using the Langmuir-Blodgett method. The films were imaged using atomic force microscopy, and three types of features were observed in various proportions: dots (circular aggregates), spaghetti (rodlike aggregates), and continents (planar aggregates). The concentration of the spreading solution on the air-water interface had the most significant effect on the types of features observed. Variations in surface pressure and compression speed had little effect on the distribution and predominance of the different types of aggregates. Single-drop experiments show that feature formation depends on a competition between film spreading and polymer entanglement resulting from solvent evaporation. Aggregates thus formed upon spreading on the air-water interface are kinetically trapped and quite stable upon transfer to the solid substrate.

We combine a self-organizing diblock copolymer system with semiconductor processing to produce silicon capacitors with increased charge storage capacity over planar structures. Our process uses a diblock copolymer thin film as a mask for dry etching to roughen a silicon surface on a 30 nm length scale, which is well below photolithographic resolution limits. Electron microscopy correlates measured capacitance values with silicon etch depth, and the data agree well with a geometric estimate. This block copolymer nanotemplating process is compatible with standard semiconductor processing techniques and is scalable to large wafer dimensions.

External electric fields were used to amplify thermal fluctuations at the interface between two thin liquid films. Similar to the results shown previously for the enhancement of fluctuations at the polymer/air interface, interfacial fluctuations having a well-defined wavelength were enhanced with a characteristic growth rate. A simple theoretical framework to describe the experimental observations is presented. Both experiment and model calculation show a substantial reduction in feature size as a result of the change in surface/interfacial energy when going from the thin film to the bilayer case. Experimentally, features develop nearly 50 times faster for the bilayers in comparison to the polymer/air case. These results point to a simple route by which the nanoscopic feature can be easily and rapidly produced or replicated.

Nonlithographic techniques for patterning structures on the nanometer scale can provide methods for direct control of particle spacing at surfaces. By using diblock copolymers, the surface density of a film can be established by the properties and area of the anchoring block, and the feature sizes can be set through the choice of free block dimensions. By depositing poly(styrene)-poly(ethylene oxide) (PS-PEO) diblock copolymers of different fractional composition of PEO on a surface by a Langmuir-Blodgett technique at different pressures, we show that the surface density of poly(styrene) aggregates can be controlled. The separation of PS aggregates on the surface is ensured by selection of the PEO composition so that its projected area is greater than that of the PS for all pressures less than that of the transition from a 2-dimensional to 3-dimensional film. The areal density of these resultant PS surface micelles can be tuned for a particular polymer composition and is linearly dependent on the deposition pressure which defines the region chosen on the phase diagram.

The antimicrobial activity of chitosan and chitosan derivatives has been well established. However, although several mechanisms have been proposed, the exact mode of action is still unclear. Here we report on the investigation of antibacterial activity and the antibacterial mode of action of a novel water-soluble chitosan derivative, arginine-functionalized chitosan, on the gram-negative bacteria Pseudomonas fluorescens and Escherichia coli. Two different arginine-functionalized chitosans (6% arginine-substituted and 30% arginine-substituted) each strongly inhibited P. fluorescens and E. coli growth. Time-dependent killing efficacy experiments showed that 5000 mg L -1 of 6% substituted and 30% substituted chitosan-arginine killed 2.7 logs and 4.5 logs of P. fluorescens, and 4.8 logs and 4.6 logs of E. coli in 4 h, respectively. At low concentrations, the 6% substituted chitosan-arginine was more effective in inhibiting cell growth even though the 30% substituted chitosan-arginine appeared to be more effective in permeabilizing the cell membranes of both P. fluorescens and E. coli. Studies using fluorescent probes, 1-N-phenylnaphthylamine (NPN), nile red (NR) and propidium iodide (PI), and field emission scanning electron microscopy (FESEM) suggest that chitosan-arginine's antibacterial activity is, at least in part, due to its interaction with the cell membrane, in which it increases membrane permeability.