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AbstractNew photochromic amorphous molecules containing core of triphenylamine and three branches of azobenzene were obtained in good yields by Pd-catalyzed amination. High glass temperature (Tg) above 100°C of these molecules was because of many triphenylamine units and high molecular weight. The stable amorphous films of these molecules could be easily prepared by spin-coated method. The photoinduced and thermal isomerization were observed in the amorphous films and the solutions. The size of the core had no clear effect on rates and activation energy values (Ea) of the cis→trans thermal isomerization in solution.

The preparation of ordered porphyrin monolayers on the solid surfaces was pursued by noncovalent bonding. Four kinds of self-assembled monolayers (SAM) that carried pyridine moieties were constructed on the surface of silver colloids (4Py-SAM from 4,4‘-dithiodipyridine, 2Py-SAM from 2,2‘-dithiodipyridine, DTPA-4Py-SAM from dithiodi[N-(4-pyridylethyl)propylamide], and DTPA-2Py-SAM from dithiodi[N-(2-pyridylethyl)propylamide]. The structure of the SAMs was observed by surface-enhanced Raman spectroscopy. When a nitrogen atom in the pyridine ring of the SAM was directed to the solution phase (in the cases of 4Py-SAM, DTPA-4Py-SAM, and DTPA-2Py-SAM), incubation of the SAM with a low concentration (<22 nM) of water-soluble porphyrin into which a zinc ion had been incorporated (zinc(II) 5,10,15,20-tetrakis(1-methylpyridinium-4-yl)porphine tetra-p-toluenesulfonate:  TMPyP Zn(II)) resulted in a definite Raman scattering corresponding to the porphyrin ring, in addition to that of the SAM itself. In the absence of zinc ion (5,10,15,20-tetrakis(1-methylpyridinium-4-yl)-21H,23H-porphine tetra-p-toluenesulfonate:  TMPyP H2), on the other hand, only the scattering of the SAM was observed. Furthermore, the 2Py-SAM, in which a nitrogen atom of the pyridine ring was directed to the silver surface, showed no scattering corresponding to the porphyrin moiety, either. These results indicated that the porphyrin ring was attached to the SAM by the axial ligand linkage between the pyridine ring of the SAM and the zinc ion of the porphyrin. It was suggested that the SAM, on which porphyrin groups were fixed in the ordered manner, would be useful as molecular optical devices.

Palladium-catalyzed amination of poly(p-bromostyrene) with 4-(phenylamino)azobenzene afforded polystyrene derivative having an aminoazobenzene group in the side chain with a high degree of substitution. Palladium-catalyzed polycondensation of aryl dibromides with 4-aminoazobenzene also gave poly(iminoarylene)s having azobenzene group in the side chain in good yields. Photoinduced and thermal cis−trans isomerization behaviors of the polymers were investigated. Comparison of isomerization rate constants and activation energy values of the polymers and the corresponding model compound showed little difference in the kinetics data between the polymers, thus suggesting no significant influence of the structure of the polymer backbone on the azobenzene cis−trans isomerization. The absorption spectra of the polymers were dependent on the acidity of media because it can exist in neutral and protonated forms.

Five kinds of polythiophenes bearing a crown ethereal subunit directly bonded to the thiophene ring have been prepared by the following organometallic polycondensation:  (i) nX−Ar−X + nNi⁰Lm → &lparendash;Ar&rparendash;n; (ii) aX−Ar−X + bX−Ar‘−X + (a + b)Ni⁰Lm → &lparendash;Ar)a(Ar‘&rparendash;b, and (iii) nX−Ar−X + nMe3Sn−Ar‘−SnMe3 → &lparendash;Ar−Ar‘&rparendash;n (Pd-catalyzed); Ar = thiophene-2,5-diyl with the crown ethereal subunit. Polythiophenes with alkoxy substituents (OCH3 and O(CH2)2OCH3) are also prepared by the organometallic polycondensation. The crown ethereal polymers exhibit photoluminescence in a range of 467−603 nm in both CHCl3 solutions and films. Their electroluminescence spectra essentially agree with the photoluminescence spectra. The crown ethereal polythiophenes have a high affinity toward Na⁺. After chemical oxidation (or p-doping) and reduction (or n-doping), the polymers show an electrical conductivity of 5.4 × 10^-7 to 1.8 S cm^-1. The Na-doped and electrically conducting state of crown ethereal polythiophenes shows some stability under air, which is attributed to the strong affinity of the polymer to Na⁺. Cyclic voltammetry of the crown and linear ethereal polythiophenes reveals a large difference (about 2 V) between n-doping and n-undoping potentials.

Poly(2,5-pyridinediyl) (PPy) and poly(2,2′-bipyridine-5,5′-diyl) (PBpy) composed of inherently π-deficient pyridine rings are soluble in formic acid, show large degree of depolarization (ϱv= 0.33) in formic acid, and show fluorescence. n-Type doping of PPy and PBpy (chemically with sodium as well as electrochemically) affords electrically conducting materials, whereas the polymers are essentially inactive against p-type doping.

Measurements of optical third-harmonic generation have been made on novel heteroaromatic π-conjugated polymer thin films. The third-order nonlinear optical susceptibility x(3) of poly(thiophene-2,5-diyl pyridine-2,5-diyl) (PTPY), which has the strongest intramolecular charge transfer among the polymers discussed in this work, is 1.5 × 10-10 esu at the near three-photon resonance wavelength.

A Ti-conjugated polymer consisting of pyrrole and fluorene units was synthesized via Ru-catalyzed direct arylation polycondensation. The introduction of a 2-pyrimidinyl substituent into the N -position of the pyrrole monomer as a directing group induced ortho-metalation, with effective site-selective polycondensation at the a-position of the pyrrole monomer, without the need for protection of the b-position. Subsequent removal of the 2-pyrimidinyl substituent led to the elongation of p-conjugation along the main chain of the polymer via elimination of the steric hindrance due to the bulky substituent.

This paper investigated dynamic responses of steel monorail bridges incorporating train-bridge interaction under strong earthquakes. Two types of steel monorail bridges were considered in the study: a conventional type with steel track-girder; an advanced type with composite track-girder and simplified lateral bracing system. During strong earthquakes, monorail train was assumed standing on the track-girder of monorail bridges. Observations through the analytical study showed that considering the monorail train as additional mass rather than a dynamic system in numerical modeling overestimated effect of the train load on seismic performance of monorail bridges. Earlier plastic deformations at the end bracing of the girder system absorbed seismic energy and reduced the stress at the pier base.

A new porous and electrically conducting clay‐carbon composite, prepared by sintering mixtures of a clay (composed mainly of kaolinite) and porous carbon, can be used as excellent positive electrodes of zinc‐oxygen primary cells and zinc‐iodine secondary cells.

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