Photosensitizer Unit Research Articles

Photoresponsive Dendritic Azobenzene Peptides

Two dendritic peptides containing a branched lysine core and up to eight azobenzene moieties in the periphery were synthesized on solid support employing the ω-amino acid 4-(aminomethyl)phenylazobenzoic acid. With an additional peptidic tail consisting of an oligolysine portion, water solubility was achieved for the dendrimers, which allowed for the characterization of the cis/trans photoisomerization of the dendritic azobenzene species in both organic and aqueous media. Despite the interactions between the chromophores, which occur particularly in aqueous media, at higher dilution the photoisomerization process was found to proceed to extents that should permit photomodulation of molecular recognition processes between ligands grafted to the photosensitive azobenzene units and receptor molecules.

Photoresponsive dendritic azobenzene peptides.

Two dendritic peptides containing a branched lysine core and up to eight azobenzene moieties in the periphery were synthesized on solid support employing the omega-amino acid 4-(aminomethyl)phenylazobenzoic acid. With an additional peptidic tail consisting of an oligolysine portion, water solubility was achieved for the dendrimers, which allowed for the characterization of the cis/trans photoisomerization of the dendritic azobenzene species in both organic and aqueous media. Despite the interactions between the chromophores, which occur particularly in aqueous media, at higher dilution the photoisomerization process was found to proceed to extents that should permit photomodulation of molecular recognition processes between ligands grafted to the photosensitive azobenzene units and receptor molecules.

Developing novel photoresists: microstructuring of triazene containing copolyester films

The growing field of microtechnology induces an increasing demand for affordable functional materials. Several strategies exist for improving the ablation behaviour of standard polymers, e.g., doping with a chromophore. Another possibility is the synthesis of copolymers containing photosensitive moieties besides standard monomers. The specialty polymers investigated in this study contain a triazene group (Ph–NN–NR 2) as the photosensitive unit; a polyester with varying contents of triazene groups is presented. These units can be situated in either the main chain or in the side chain. Under irradiation the photosensitive chromophores are cleaved fast and irreversibly. Spectroscopic evidence shows the loss of nitrogen to be the initial photochemical decomposition step. For a comparison of the performance of copolymers with different fractions of triazene groups in the backbone, we have determined the threshold fluences and the effective absorption coefficients. With respect to these ablation parameters, only small differences were found within the set of copolymers investigated. From atomic force microscopy (AFM) and scanning electron microscopy (SEM) it becomes evident that a minimum content of triazene groups in the main chain is necessary for defined microstructures with sharp edges, whereby a resolution in the sub- μm scale has been achieved. At lower concentrations no sharp structures are formed; at high concentrations bubbles impair the quality of the structures.

New polyesters with photosensitive backbones based on the triazene unit

The synthesis of photosensitive polymers that contain the triazeno group (Ph-N=N-NR 2 ) as a sensitive unit in their backbone is reported. The synthesis pathway consists of difunctional alcohols incorporating the photosensitive unit that react with diacyl derivatives to give the respective polyesters. Upon irradiation, the photosensitive chromophores both in monomeric and polymeric surroundings are cleaved fast and irreversibly, as shown in photolytic studies and their kinetic evaluations. Thermogravimetrical investigations indicate the loss of nitrogen being the initial thermal decomposition step and exhibit stabilities sufficient for the requirements in applications as photoresists.

A New Type Terminal Functionalized Photosensitive Polyimide Resin: Synthesis and Characteristics.

A new type terminal functionalized photosensitive polyimide resin comprising terminal functionalized polyamic acid. acrylate monomer, photosensitizer and tetrazole derivatives has been developed. Structure of polyamic acid can be easily changed by the selection of diamines and acid di-anhvdrides without any effect on the photosensitivity, because the photosensitive units are located only at the both terminals of the polyamic acid. Therefore. the control of thermal expansion coefficient and control of film properties are easily allowed. The new photosensitive polyimide which has carboxylic groups in polyamic acid forms a undesirable residual layer on copper. It is found that an addition of tetrazole derivatives to the system drastically prevents the formation of residual layer which permits this photosensitive polyimide to produce fine patterns on copper substrates. Mechanism of tetrazole derivatives to prevent residual layer formation is discussed.

Photo-Memory System Based on the Photo-Isomerization Behavior of the Azobenzene Unit in the Main Chain of Polyimide Lb Films

Abstract Polyamic acid derivatives containing photosensitive azobenzene units in their main chain have been synthesized. Y type polyamic acid LB films were fabricated which were then converted into the polyimide LB films by chemical imidization accompanied by the elimination of long alkyl amines. The orientation of the polymer chains to the dipping direction was observed by the orientation of the chromophore in the plane direction, which depends strongly on the structure of the diamines. Aromatic diamines lead to a preferential orientation parallel to the dipping direction, while aliphatic diamines did not result in a preferential orientation. The reversible photo-isomerization was caused by both the polyamic acid and polyimide LB films. The rigid aromatic polyimides showed less reactivity compared with the more flexible aliphatic polyimides.

論文特集「有機・無機の光機能材料」 ニトロ化ポリアセナフチレンの合成とその高分子増感剤としての応用

Polymers having photosensitive nitroaryl groups were synthesized by the nitration of polyacenaphthylene or by the ionic polymerization of 5-nitroacenaphthylene. The photoisomerization of trans-cinnamic acid in the presence of photosensitizers was carried out in DMF. From the results obtained, it was found that the partially nitrated polyacenaphthylene reveals an excellent photosensitizing activity compared with that having 100% photosensitizer unit and that its sensitivity depends on the content of the nitro group.

Preparation and properties of new photosensitive polyimides from bis(4‐aminophenyl)tetramethyldisilane and various aromatic tetracarboxylic dianhydrides

AbstractNew photosensitive polymides containing photosensitive disilane unit were synthesised from 1,2‐bis(4‐aminophenyl)tetramethyldisilane and various aromatic tetracarboxylic dianhydrides by the usual two‐step procedure that includes ring‐opening polyaddition to yield the precursor polyamic acids, followed by cyclodehydration giving the respective polyimides. The polymaic acids had inherent viscosities between 0.63 and 0.85 dL/g depending on the tetracarboxylic dianhydride used. Excepting the polyimide obtained from pyromellitic dianhydride, all other polyimides were soluble in N‐methyl‐2‐pyrrolidone, m‐cresol, and pyridine. While the polyimide containing diphenyl sulfone unit was amorphous, the other polyimides were semi‐crystalline polymers based on their x‐ray diffractograms. The polyimides had glass transition temperatures between 235 and 304°C. They were thermally stable up to 380°C in both air and nitrogen atmospheres. All the polyamic acids showed a drastic decrease in the inherent viscosity upon UV light irradiation, implying the inherent photosensitivity of the polymers containing the disilane moiety.

Synthesis and characterization of new photosensitive poly (oxyaryleneoxydisilane)s from 1,2‐bis (diethylamino) tetramethyldisilane and various bisphenols

AbstractA new class of polymers containing a photosensitive disilane unit in the polymer main chain with inherent viscosities between 0.1 and 0.59 dL/g was prepared by the melt polycondensation of 1,2‐bis (diethylamino) tetramethyldisilane and various bisphenols. The polymers were characterized by UV, IR, 1H‐NMR, and elemental analysis. Poly(oxyaryleneoxydisilane)s were soluble in a variety of common organic solvents and have a wide range of glass transition temperatures varying between −65 and 135°C, depending on the arylene structure. Most of the polymers were stable up to 350°C in both air and nitrogen atmospheres. The inherent viscosity of the polymer containing the 1,6‐napthalene unit decreased drastically upon UV light irradiation, indicating its photodegradation.

Molecular photodiodes consisting of polyimide Langmuir–Blodgett films possessing electron acceptor, photo-sensitizer, and electron donor units

Molecular photodiodes possessing high efficiency for light–electricity conversion are constructed from polyimide Langmuir–Blodgett films consisting of electron acceptor, photo-sensitizer, and electron donor units.

Synthèse et réactions photochimiques d'homopolymères et de copolymères de la p‐vinylbenzophénone et du vinylferrocène

AbstractPoly(p‐vinylbenzophenone), (poly[1‐(4‐benzoylphenyl)ethylene]), (PVB) has been synthesized for the first time directly from its monomer p‐vinylbenzophenone (VB) the preparation of which was improved. In a second step, copolymers containing blocks of photosensitive VB units separated by isolated quenching vinylferrocene (VF) units have been prepared. PVB and the VB‐VF copolymers were irradiated in the presence of isopropyl alcohol in benzene solutions. The benzophenone groups inserted in these macromolecular chains obey the same reaction scheme as the photoreduction of the small molecule of benzophenone. However, recombination of the radicals located along the polymeric chain leads to intra‐ and intermolecular reactions changing drastically the macromolecular morphology by the formation of cycles and networks and by chain scissions. The quantum yields of the photochemical transformations were measured, but they could not be related quantitatively to morphological parameters. In all cases the ferrocene group inhibits strongly the photochemical reaction.