No abstract

We report a new fabrication method of a thin polymer film with regular array of micropores (honeycomb film). A honeycomb film was fabricated by depositing a dilute solution of an amphiphilic polymer on water surface. The honeycomb film transferred onto a solid substrate was characterized by atomic force microscopy. By this fabrication method, it was possible to control film area, pore diameter, and film thickness. The pore size depended upon the evaporation time of the polymer solution spread on water surface. The thickness of a honeycomb film was controlled by spreading area of the polymer solution. The spreading behavior was influenced by the water temperature. The film area was proportional to the volume of spread polymer solution and controlled by changing the sub-phase temperature, too. When the polymer solution was simply cast on a solid substrate, a thin polymer layer remained in the bottom of the honeycomb pores. On the other hand, the honeycomb film fabricated on water surface has no bottom layer in its pores. A self-standing honeycomb mesh is formed by the “on-water spreading” method.

In gelation chemistry, catechol groups are used as cross-linking points. Both oxidation and coordination effects of catechol were investigated for their unique features in chemistry by spectroscopic measurements. Polystyrene copolymers containing catechol groups were synthesized by free radical copolymerization of styrene and N-2-(3′,4′-ditriethylsilyloxyphenyl)ethyl methacrylamide, and the successive deprotection reaction was catalyzed by tetra-n-butylammonium fluoride. The copolymer containing catechol units afforded a dual cross-linking system based on completely different coordination and oxidation chemistries, and the competing cross-linking mechanisms are discussed. These findings are useful and important for paving the way for designing a novel bioinspired artificial adhesive surface coating and curing system.

In nearly all applications of ultrafast multidimensional infrared spectroscopy, the spectral degrees of freedom (e.g., transition frequency) and the orientation of the transition dipole are assumed to be decoupled. We present experimental results which confirm that frequency fluctuations can be caused by rotational motion and observed under appropriate conditions. A theory of the frequency-frequency correlation function (FFCF) observable under various polarization conditions is introduced, and model calculations are found to reproduce the qualitative trends in FFCF rates. The FFCF determined with polarization-selective two-dimensional infrared (2D IR) spectroscopy is a direct reporter of the frequency-rotational coupling. For the solute methanol in a room temperature ionic liquid, the FFCF of the hydroxyl (O-D) stretch decays due to spectral diffusion with different rates depending on the polarization of the excitation pulses. The 2D IR vibrational echo pulse sequence consists of three excitation pulses that generate the vibrational echo, a fourth pulse. A faster FFCF decay is observed when the first two excitation pulses are polarized perpendicular to the third pulse and the echo, 〈XXY Y〉, than in the standard all parallel configuration, 〈XXXX〉, in which all four pulses have the same polarization. The 2D IR experiment with polarizations 〈XY XY〉 ("polarization grating" configuration) gives a FFCF that decays even more slowly than in the 〈XXXX〉 configuration. Polarization-selective 2D IR spectra of bulk water do not exhibit polarization-dependent FFCF decays; spectral diffusion is effectively decoupled from reorientation in the water system.