Fusae Nakanishi

Synthesis and nonlinear optical properties of a new polydiacetylene derivative having sulfur atom directly bound to the main chain

In order to reduce the band gap of polydiacetylene, a new class of polydiacetylene derivative having sulfur atom directly bound to the main chain was synthesized. The solid state polymerization of the new diacetylenes occurs in the manner of the topochemical and topotactic 1,4-addition reaction. The evidence of the electron donating effect of the sulfur atoms of the polydiacetylenes is obvious in the red shift of the absorption maximum and the asymmetrical bond length alternation of the main chain.

PREPARATION OF 1-ALKYNYL 2-(TRIMETHYLSILYL)ETHYL SULFIDES AS THIOLATE ANION PRECURSORS FOR SELF-ASSEMBLED MONOLAYERS

Abstract Syntheses of 1-alkynyl 2-(trimethylsilyl)ethyl sulfides are reported. Deprotection of 2-(trimethylsilyl)ethyl groups using fluoride ions permits the formation of thiolate anions which are trapped by in situ alkylation with methyl iodide and can be used to produce self-assembled monolayers on gold.

Stability of a photoreactive polymer LB film

Abstract Dynamic contact angles and their hysteresis for LB films of p-phenylenediacrylic acid monodecylester (p-PDAmC10) and poly (vinyl alcohol) bearing p-PDAmC10 as the side chain (PVA-p-PDAmC10) were investigated by the Wilhelmy plate method. The hysteresis loops of the contact angle showed that: (1) PVA-p-PDAmC10 forms a more stable LB film than that of p-PDAmC10 which is casily detached when contacted with water; (2) PVA-p-PDAmC10 LB film transferred at high surface pressure (≤20 mN/m) with more than 3 layers can provide a uniform surface and same wettability; (3) PVA-p-PDAmC10 LB film has a very large contact angle hysteresis (>80°), which means that reorientation of the surface configuration takes place dramatically; and (4) the hysteresis can be greatly reduced (<30°) by UV-irradiation due to the photocycloaddition in the side chains of PVA-p-PDAmC10.

Photopolymerization of amphiphilic diolefins in mono- and multilayers

Abstract Photoreactive thin films were prepared from amphiphilic diolefins using the Langmuir-Blodgett technique and their photoreaction was investigated. p-Phenylenediacrylic acid (P-PDA) monoesters having long-chain alkyl ester residues were found to form stable monolayers on CdCl 2 KHCO 3 aqueous solution and they were transferred onto a substrate with Z-type deposition. The u.v. and fluorescence spectra of the multilayers showed that p-PDA monoester molecules are arranged side by side with the stacking of aromatic rings. The linear relationship observed between absorbance and the number of the layers supports the successful formation of multilayers. On irradiation, double bonds reacted to form cyclobutane rings and the subsequent cycloaddition led to the formation of oligomers and then polymers.

Aliphatic poly(amido acids) and polyimides with cyclobutane ring in the main chain

Abstract New aliphatic polyimides with cyclobutane ring in the main chain have been synthesized successfully from cyclobutane tetracarboxylic dianhydride and diamine. In order to establish the reaction path poly(amido acids), intermediates to polyimides, were isolated and characterized. All poly(amido acids) are hygroscopic and were found to be converted into polymides through dicarboacetoxy intermediate by heating in dimethylformamide at 100°C in the presence of acetic anhydride. Thermal study by means of thermal gravimetric analysis and differential scanning calorimetry revealed that conversion of poly(amido acid) to polyimide also occurred by thermal cyclocondensation reaction at around 180°C. These reactions were confirmed by parallel reaction of the model compounds. Properties of polyimides thus obtained were characterized and are discussed in comparison with known polymers with polyimide or cyclobutane ring structures.

Investigation of the Origin of the Topochemical Arrangement in Photoreactive 2-Benzyl-5-benzylidenecyclopentanone Crystal

Abstract Investigation of the origin of a dimeric pair structure of the title compound molecules in a crystal was extensively conducted. Molecular dynamics calculations suggested that conventional van der Waals and electrostatic estimations did not accurately reproduce the temperature dependence of the interatomic distance of the dimeric pair, as observed in X-ray structure analyses. A dimeric pair formation of the monomer in a solution was also observed by spectroscopic studies. X-ray structure analysis of a photodimer crystal revealed that the packing motif of the monomer crystal is quite similar to the dimer crystal. It is speculated that, on crystallisation from a solution, the monomer molecule form a dimeric structure near the crystal surface and make a stack similar to the dimer crystal.

Synthesis, structures, and conformational analysis of dibenzodioxadisilocins

Abstract Novel dibenzodioxadisilocins were prepared using a dehalogenative coupling reaction between (2,6-dichlorophenoxy)t-butyldimethylsilane and dimethyldichlorosilane with magnesium via an intramolecular 1,3-anionic rearrangement of the silyl group. Their structures were unequivocally confirmed by X-ray crystallography. For a comparison with the X-ray data, molecular orbital calculations on the conformations of the organosilicon macrocyclics were also carried out.

Photochemical behaviour of poly(vinyl alcohol) bearing p-phenylenediacrylate groups

Spectral features and photochemical reactivities were studied on poly(vinyl alcohol) bearing p -phenylenediacrylate groups (PVA- p -PDAmC 2 ) in comparison with ethyl hydrogen p -phenylenediacrylate ( p -PDAmC 2 ). PVA- p -PDAmC 2 has a very high photoreactivity compared with p -PDAmC 2 ; this can be ascribed to the formation of ground state pairs of p -PDAmC 2 moieties as side chains due to repulsive interaction between the hydrophobic side chains and the hydrophilic main PVA polymer chain. Some polymers showed features of photoresist with a resolution of 2.5 μ m.

Effects of protic solvents upon intramolecular interaction of polymethylene bis-p-phenylenediacrylates

Abstract Measurements of fluorescence spectra of a series of polymethylene bis( p -(2-ethoxycarbonylvinyl)cinnamates) [(CH 2 ) n ( p -PDAmC 2 ) 2 ( n =2–12)] in various solvents indicate that alcoholic solvents induce intramolecular association of the diacrylate chromophores, exhibiting excited pair emission, of which the intensity is dependent upon the methylene chain length.

Depolymerization behaviour of poly-(p-phenylene diacrylic acid diethyl ester)

Abstract The photochemical and thermal behaviour of poly(p-phenylene diacrylic acid diethyl ester) [poly(p-PDA-Et)] has been investigated. It was observed that both photo and thermal depolymerization occurs with cleavage of the cyclobutane ring. Photochemically poly(p-PDA-Et) in solution depolymerizes selectively into oligomer, which undergoes cis-trans isomerization without further depolymerization to monomer. On the other hand, it depolymerizes thermally at random into low molecular weight polymer and monomer.