Study of Gases Permeation in Necklace-Shaped Dimethylsiloxane Polymers Bearing POSS Cages.

The transport of small gases (H, CO, N, O) through a series of novel membranes based on necklace-shaped inorganic polymers (DMS@POSS), in which a polyhedral oligomeric silsesquioxane (POSS) cage unit and soft chains of oligo-dimethyl siloxane (DMS) were alternately connected, was investigated. The influence of the DMS chain length and crosslinking density of the DMS@POSS on membrane properties were studied. The membranes revealed characteristic structure-property relation towards both glass transition and gases transport.

Photoisomerization and thermal isomerization of shuttlecock- and bowl-equipped (phenylazo)pyridines.

The photoisomerization and thermal isomerization of sterically hindered (phenylazo)pyridine derivatives with a shuttlecock-shaped (TbetNNPy) or a bowl-shaped framework (BmtNNPy as well as the azoxy counterpart, BmtNN(O)Py) have been investigated. The crystal structures of these compounds revealed a planar conformation of the (phenylazo)pyridine moiety for TbetNNPy and severely distorted conformations for BmtNNPy and BmtNN(O)Py. The quantum yields of the trans-to-cis photoisomerization of TbetNNPy and BmtNNPy is lower than those of unsubstituted (phenylazo)pyridines.

Photoisomerization and thermal isomerization of arylazoimidazoles.

Photoisomerization and thermal isomerization behaviors of an extensive series of arylazoimidazoles are investigated. Absorption spectra are characterized by a structured pipi* absorption band around 330-400 nm with a tail on the lower energy side extending to 500 nm corresponding to an npi* transition. The trans-to-cis photoisomerization occurs on excitation into these absorption bands.

Photochromism of 2-(phenylazo)imidazoles.

The isomerization behaviors of 2-(phenylazo)imidazole (Pai-H) and 1-N-methyl-2-(phenylazo)imidazole (Pai-Me) have been investigated. The crystal structure of trans-Pai-Me was determined, revealing that key structures around the azo group are nearly identical among azobenzene, Pai-H, and Pai-Me. Pai-Me undergoes reversible cis/trans photoisomerization, whereas Pai-H responds poorly to irradiation.