Three-dimensionally ordered array of air bubbles in a polymer film.

We report the formation of a three-dimensionally ordered array of air bubbles of monodisperse pore size in a polymer film through a templating mechanism based on thermocapillary convection. Dilute solutions of a simple, coil-like polymer in a volatile solvent are cast on a glass slide in the presence of moist air flowing across the surface. Evaporative cooling and the generation of an ordered array of breath figures leads to the formation of multilayers of hexagonally packed water droplets that are preserved in the final, solid polymer film as spherical air bubbles. The dimensions of these bubbles can be controlled simply by changing the velocity of the airflow across the surface. When these three-dimensionally ordered macroporous materials have pore dimensions comparable to the wavelength of visible light, they are of interest as photonic band gaps and optical stop-bands.

Solid-state multipulse proton Nuclear Magnetic Resonance (NMR) characterization of self-assembling polymer films.

Multipulse solid-state proton Nuclear Magnetic Resonance (NMR) has been used to study the domain structure in poly(styrene-b-isoprene-b-styrene) triblock copolymers in clear and self-assembled polymer films. Films containing ordered arrays of microcavities (3-5 microm) were obtained by casting the polymer from carbon disulfide solution in a moist environment, while clear films were obtained by solvent evaporation under nitrogen. The domain sizes for the polystyrene and polyisoprene blocks were measured by proton spin diffusion using the dipolar filter pulse sequence. The domain sizes for the dispersed phase and the long period were measured to be in the range of 3-6 nm, depending on the polymer molecular weight, and no differences domain size were observed for the clear and the self-assembled polymer films.

Photon tunneling microscopy of polymeric surfaces.

With photon tunneling microscopy it is possible to image polymeric and other dielectric surfaces by means of the unusual properties of photon tunneling or evanescent waves. Vertical resolution is 1 nanometer, limited by the detector, over a vertical range of half a wavelength. Lateral resolution is better than a quarter of a wavelength over a field of view up to 125 micrometers. Samples can be surveyed in real time in air, with no need for metallization, and without shadowing or the intrusive effects of electrons or scanning probes. The use of this technique to study single crystals of polyethylene and processes such as latex film formation and the evolution of polystyrene topography while dewetting above the glass transition temperature are described.