JPH02102254A - Langmuir-blodgett film and its production - Google Patents

Abstract

PURPOSE:To obtain a photosensitive, highly functional organic thin film which can reversibly undergo cis-trans photoisomerization by forming a polyion complex from a long-chain azobenzene derivative terminated with an anion and polyvinylamine. CONSTITUTION:A photosensitive Langmuir-Blodgett film(LB film) is prepared by forming a polyion complex from a 20-50C long-chain azobenzene derivative terminated with an anion, such as 4-octyl-4'-(5-carboxypentamethyleneoxy) azobenzene, and polyvinylamine. This film can be prepared by casting a chloroform solution of the azobenzene as a film-forming substance on a solid substrate by using a dilute aqueous solution of polyvinylamine as an underlayer water and is used as a photochromic material of e.g., an ultrahigh density photomemory or a photoswitching device.

Description

[Detailed description of the invention] [Industrial application field] Langmuir-Blodgett film (hereinafter abbreviated as LB film) having a photosensitive structural unit is used as a photochromic material for ultra-high density optical memories, optical switching devices, etc. This is a useful functional organic thin film that is expected to be applied to

[Prior art and its problems] LB films containing azobenzene can be used to create thin films with ultra-high density optical memory and optical switching functions by utilizing the cis and trans photoisomerization reaction ability of the azobenzene moiety during LB film formation. It is expected to be applied to manufacturing.

Conventionally, the method for manufacturing LB films containing azobenzene moieties is as follows:
A method is known in which a solution of an azobenzene long-chain derivative having an anionic group at a terminal position is formed into a film on a lower layer of water containing multivalent inorganic ions such as calcium ions, barium ions, and cadmium ions. However, the LB film obtained by this method has the problem that in order to control its photoisomerization reaction ability, the free space of the azobenzene moiety is small and the isomerization reaction does not proceed in the direction where the molecular occupied area increases. there were.

[Means for Solving the Problems] The present inventors have discovered that an azobenzene long-chain derivative having an anionic group at the terminal position forms a polyion complex with polyvinylamine, increases the free space of the abbenzene moiety, and forms an LB. The present invention was achieved by discovering that reversible cis and trans photoisomerization reactions in membranes are possible.

An object of the present invention is to provide a highly functional organic thin film in which an azobenzene moiety can undergo a reversible cis-trans photoisomerization reaction during LB film formation.

The above-mentioned object of the present invention resides in a photosensitive LB film formed by forming a polyion complex between an azobenzene long-chain derivative having 20 to 50 carbon atoms and an anionic group at the terminal position and polyvinylamine, and a method for producing the same.

As the azobenzene long-chain derivative having an anionic group used in the production of the LB membrane of the present invention, any azobenzene long-chain derivative having 20 to 50 carbon atoms and having an anionic group at the terminal position can be used.

A preferred azobenzene derivative is a compound represented by the following general formula (1).

(Here, X, Y are -CH,, -1-0-1S--NH
-1 and a lower alkyl group R which may have a substituent represent a divalent group such as monoNR-, where n is an integer from 3 to 12, m is an integer from 2 to 11, and A is an integer from 2 to 11. Anions such as a carboxyl group, a sulfone group, a sulfate ester group and a phosphate ester group. Particularly preferred azobenzene derivatives are compounds having a carboxyl group at the terminal position. Examples of preferred compounds include 4-octyl-4'-(5-carboxypentamethyleneoxy)azobenzene, 4-hexyloxy-4'-(5-carboxypentamethyleneoxy)azobenzene, 4-dodecyloxy-4'-(5 -carboxypentamethyleneoxy)azobenzene, 4-octyl-4'(4-carboxymethyleneoxy)azobenzene, 4-butyl-4'-(10-carboxydecamethyleneoxy)azobenzene, 4-hexylthio 4'-(5-
carboxypentamethyleneoxy)azobenzene, 4-
Hebutyl-4'-(5-carboxypentamethyleneoxy)azobenzene, 4-octyl-4'-(5-carboxypentamethyleneoxy)-3'-methoxy-azobenzene, 4-octyl-4'-(5-carboxypentamethyleneoxy) Examples thereof include (methyleneoxy)-3'-methylazobenzene, 4-octyloxy-4'-(5-carboxypentamethylenethio)azobenzene, and the like.

Any polyvinylamine can be used for producing the LB film of the present invention, regardless of its production method.

For example, hydrazine modified polyvinyl fucurimide,
Examples include hydrolysates of polyvinylamine me-1, solvate reaction products of polyN-vinylamide, and Hofmann decomposition products of polyacrylamide, and in particular, solvates of polyN-vinylformamide or polyN-vinylacetamide. Reactants are preferred. A preferred method for producing polyvinylamine is to polymerize a 5 to 60% by weight aqueous solution of N-vinylformamide or N-vinylacetamide at a temperature of 40 to 80°C in the presence of a radical polymerization initiator. This method is obtained by modifying a molecular weight water-soluble polymer under acidic or basic conditions.

The LB film can be formed by using a commonly known LB film manufacturing method by using a dilute aqueous solution of polyvinylamine as the lower layer water. For example, a method is exemplified in which a 0.01 to 0.1% aqueous solution of polyvinylamine is used as the lower layer water and a long chain azobenzene derivative, which is a membrane material, is developed as a chloroform solution.

It is preferable to select conditions suitable for the pH of the lower layer water to generate a polyion complex.

When using a highly dissociable abbenzene long-chain derivative, it is possible to form a film over a wide pH range; however, when the anionic group of the azobenzene long-chain derivative is a carboxyl group, the pH should be adjusted to 6. It is preferable to make it more than that.

Generally known methods are used to form the film and to form the cumulative film.

The molecular occupied area of the obtained film is determined from the surface pressure-area curve measured using a Langmire trough measuring device.

For example, in the LB membrane of the present invention, a significant increase in the molecular occupied area is observed when compared to the case where barium ions are used in the lower layer water. For the photoisomerization reaction of the LB film, for example, the light from a 500 watt mercury lamp is converted into ultraviolet light (360 watts) using a monochromator.
LB film using barium ions in the lower layer water shows no photoisomerization reaction, whereas the LB film using the method of the present invention shows no photoisomerization reaction after 30 minutes of irradiation. A photoisomerization reaction is observed.

[Examples] Hereinafter, the present invention will be explained in more detail with reference to Examples.
The present invention is not limited to the following examples unless it exceeds the gist thereof.

Example 1 and Comparative Example 1 As a membrane material, 4-octyl-4'-(5-carboxypentamethyleneoxy)azobenzene (manufactured by Isotope Kagaku Co., Ltd.)
was used. Polyvinylamine is a sample with a molecular weight of 180,000 obtained from hydrochloric acid hydrolysis of polyN-vinylformamide (
(manufactured by Mitsubishi Kasei Corporation) was used.

The membrane material was developed as a chloroform solution on lower layer water containing 0.04 mmol/liter of polyvinylamine, and a surface pressure-area curve was measured using a Langmire trough manufactured by Kyowa Interface Science. The LB film was formed on a quartz plate or a calcium fluoride plate that had been hydrophobized with iron stearate.

The photoisomerization reaction of the LB film is carried out using a monochromator using light from a 500 watt mercury lamp, ultraviolet light (360 nm), visible light (
435 nm) and irradiated for 30 minutes.

In the absorption spectrum of the film after irradiation, absorption corresponding to trans-azobenzene at 300 to 400 nm decreased, and absorption at 400 to 500 nm corresponding to cis form was observed.

As a comparative example, the same treatment as in Example 1 was carried out except that a mixed solution of 0.3 mmol/liter of barium chlorate and 0.3 mmol/liter of sodium bicarbonate was used as the lower layer water. Almost no photoisomerization reaction was observed in the absorption spectrum of the film after irradiation.

These results are shown in Table 1.

[Effect of the invention] Azobenzene long-chain derivatives having anionic groups at terminal positions form polyion complexes with polyvinylamine to increase the free space of azobenzene moieties, resulting in reversible cis and trans photoisomerism during LB film formation. We found that the chemical reaction becomes possible. The LB film of the present invention is a photosensitive, high-performance organic thin film in which the azobenzene moieties can undergo reversible cis and trans photoisomerization reactions, and is used for photochromic applications such as ultra-high density optical memories and optical switching devices. It is expected that it will be applied to mink materials.

Claims (2)

[Claims] (1) 20 to 50 carbon atoms with anionic group at the terminal position
A photosensitive Langmuir-Blodgett film made of a long-chain azobenzene derivative and polyvinylamine forming a polyion complex. (2) Photosensitivity characterized by accumulating on a solid substrate a monomolecular film of a long-chain azobenzene derivative having 20 to 50 carbon atoms and having an anionic group at the terminal position, formed on a lower water layer containing polyvinylamine. A method for producing a Langmuir-Blodgett membrane.