Electrically Conductive Gels Prepared from Syndiotactic Polystyrene and an Ionic Liquid.

Syndiotactic polystyrene (SPS) physical gels containing a large amount of the ionic liquid 1-butylpyridinium bromide ([C4py]Br) were systematically prepared and their physical properties were examined in detail. The gels had stable forms for a long time, having storage elastic modulus values of normal gels. They showed nearly the same values of the electrical conductivity (∼7 mS/cm) as those of the mixed solutions of [C4py]Br, suggesting that the distribution of [C4py]Br was uniform in these gels and that the charge transportation in these SPS gels was not interrupted by a three-dimensional network of SPS fibrils consisting of the SPS δ crystalline phases.

Polymerization of Aniline in Tubular Cavities of the Crystalline Phase of Syndiotactic Polystyrene: Proposal of a Preparation Method of Sophisticated Polymer Composites.

Syndiotactic polystyrene (SPS) has a unique crystalline phase, named ε, that has a tubular cavity inside. We connected these cavities by optimizing the solvent used to process the films and to polymerize aniline within these channeling cavities only by immersing the films in degassed hydrochloric acid solutions of ammonium persulfate. We succeeded in fixing pentameric to octameric oligoaniline in the cavities of the SPS ε crystalline phase. This is a new and sophisticated preparation method of polymer composites between SPS and linear oligomers/polymers within its long-connected tubular cavities.

Volume Phase Transition of Chemically Cross-linked Curdlan Hydrogels Dependent on pH.

Curdlan is a polysaccharide that is expected to work as a gene carrier. We synthesized chemically cross-linked Curdlan (CCC) gel and examined its characterization. CCC gels were swollen with alkaline water over pH ∼10.2, but shrunk with acid and neutral water. Swelling ratios of the present CCC gels with water were found to be 45 times at the most and dependent on the fraction of cross-linker reagent. These volume phase transition gels that are sensitive to pH are useful and ecological as a biocompatible and biodegradable material.

Induction of female-to-male sex change in adult zebrafish by aromatase inhibitor treatment.

This study investigated whether undifferentiated germ and/or somatic stem cells remain in the differentiated ovary of a species that does not undergo sex changes under natural conditions and retain their sexual plasticity. The effect of aromatase inhibitor (AI)-treatment on sexually mature female zebrafish was examined. A 5-month AI treatment caused retraction of the ovaries after which testes-like organs appeared, and cyst structures filled with spermatozoa-like cells were observed in sections of these tissues. Electron microscopic observations revealed that these cells appeared as large sperm heads without tails. Sperm formation was re-examined after changing the diet to an AI-free food. A large number of normal sperm were obtained after eight weeks, and no formation of ovarian tissue was observed. Artificial fertilization using sperm from the sex-changed females was successful. These results demonstrated that sex plasticity remains in the mature ovaries of this species.

Entanglement of polymer chains in ultrathin films.

This investigation aimed to clarify the issue of whether polymer chains are entangled in ultrathin films spin-coated onto substrates. This was done using a fluorescence probe method to observe the behavior of two types of poly(methyl methacrylate) (PMMA), one having a carbazolyl (Cz) moiety (PMMA-Cz) and the other having an anthryl (At) moiety (PMMA-At). In both cases, the moiety fraction was 1 unit for 400 units of polymer. We prepared ultrathin films (thickness: 4-88 nm) on quartz substrates from PMMA-Cz, PMMA-At, and a mixture of the two using a spin-coating method. When the PMMA films prepared from the mixture of the two PMMAs were excited at 292 nm, which is preferentially absorbed by Cz rather than At, the Cz fluorescence was found to be quenched dramatically while the At fluorescence increased significantly. This effect is due to the proximity of the Cz to the At, which permits the transfer of excitation energy between them. The average distance between Cz and At can be calculated using the Förster mechanism. When the ultrathin film thickness was between 12 and 88 nm, the average distance was found to be 2 nm. This is much shorter than the radii of gyration of the polymers. From this it is clear that two polymer molecules in an ultrathin film do experience entanglement, as has been hypothesized. Thus, we conclude that the difference between certain properties of ultrathin films and the properties of the same materials in bulk are not induced by a decrease in the level of polymer chain entanglement.