IE904424A1

IE904424A1 - Layer element and processes for its production

Info

Publication number: IE904424A1
Application number: IE442490A
Authority: IE
Original assignee: Hoechst Ag
Priority date: 1989-12-09
Filing date: 1990-12-07
Publication date: 1991-06-19
Also published as: JPH03256738A; EP0432619A3; DE3940712A1; FI906007A; EP0432619A2; CA2031786A1; FI906007A0; KR910011790A

Abstract

A sandwich element useable for NLO purposes can be manufactured by the Langmuir-Blodgett technique. The sandwich element comprises a solid base supporting at least two thin films of regular structure which contain at least one amphiphilic compound of the general formula (I) where R<1> is H(CH2)n, H(CH2)n or R<2> and R<3> are independently of one another H, H(CH2)p, H(CH2)p or X is a single bond, -CH=CH-, -N=N-, -CH=N-NH- or -CH=N, Y is a divalent radical O, NH or S, R<4> is -H, -CO-(CH2)t, (CH2)t<-H> or YR<4> is -COO<->, -CONH2, H, OH, SO2(CH2)u, -CO2(CH2)t or -CO2(CH2vOH), Z is at least partly a polyanion, l is 1-10, n is 10-25, m is 0-25, p is 10-25, q is 10-25, r is 0-25, t is 0-25, u is 1-20 and v is 2-10.

Description

HOECHST AKTIENGESELLSCHAFT HOE 89/F 390 D.Ch.SY/Le Description Layer element and processes for its production The present invention relates to a film applied to a 5 substrate, which film comprises at least 2 monomolecular amphiphilic pyridinium layers stabilized by a polyanion.

Nonlinear optics (NLO) is of great importance for the future development of information technology, due to its potential for ‘rapid signal processing and transfer and for new methods in data processing. Specific organic compounds have higher efficiencies and shorter switching times than the conventional inorganic substances for nonlinear optics.

A substance has nonlinear optical properties if the polarization P, which is generated by the interaction between the substance and a strong electric field (a laser beam or a strong direct voltage field), depends on the higher powers of the field strength, according to the following equation: P = *(D * Εχ + X(2) : ΕχΕ2 + X(3) : E1E2E3 + ... x (1), χ (2) and χ (3) are the susceptibilities of the 1st, 2nd and 3rd order. is the electric field which can contain components of several frequencies. NLO interactions can give rise to fields with new frequencies and can change the refractive indices of the material.

Susceptibilities χ (2) and χ (3) depend on the molecular hyperpolarizabilities β and 7.

Important nonlinear optical effects depending on χ (2) are doubling of the frequency of a light beam, in par30 ticular a laser beam, parametric reinforcement of a weak light signal and electrooptical conversion of electric - 2 signals. To obtain 2nd order effects, the active molecules have to be aligned non-centrosymmetrically, since for centrosymmetrical substances χ (2) is zero.

One process which enables the production of films having 5 a particularly favorable alignment for NLO is the Langmuir-Blodgett (LB) process. In this process, molecules are spread on a water surface, aligned in parallel by reducing the area per molecule and applied to a substrate by immersion and withdrawal of a base material at a constant surface pressure. In each immersion operation, one monomolecular layer is transferred with its order intact. Amphiphilic molecules, i.e. molecules having a hydrophilic end (a head) and a hydrophobic end (a tail) are used for building up the LB layers.

Multilayers for use in optical structural components require repeated immersion operations.

To obtain LB layers having high 2nd order susceptibilities, organic compounds having not only high molecular 2nd order hyperpolarizabilities β but also amphiphilic properties are used as the starting material.

A compound has a large β value if it contains a conjugated electron system (for example a benzene ring) in which one or more electron donor groups and one or more electron acceptor groups are incorporated. A hydrophobic group is incorporated at the donor or acceptor end. The hyperpolarizability is increased if the molecule absorbs light in the wavelength range of the irradiating electric field or the field produced by the NLO (so-called resonance amplification). However, absorptions are undesirable in many applications since they give rise to losses and have an adverse effect on optical stability (level of light intensity which is tolerated without any permanent material defects). An ideal compound is one which has high hyperpolarizability without having strong absorption in the desired wavelength range. - 3 It was already known that the pyridinium compound of the formula la (CH3(CH2)15)2 N-, CH=CHn+-ch3 I (la) and similar compounds have very good NLO properties in 5 monolayers (Lupo et al., J. Opt. Soc. Amer., B 5, 500 (1988)). Using these pyridinium compounds or similar dyes containing monovalent anions, it is usually not possible to apply more than one double layer; further immersion operations do not result in further transfer of the dye.

Moreover, the dye layers comprising monovalent anions are usually stable only up to 70’C.

The object was therefore to stabilize a film composed of amphiphilic pyridinium compounds in such a manner that several monolayers can be transferred in succession with the formation of multilayers. At the same time, the thermal stability (compared with the known films) should be improved, if possible.

A layer element has now been found which comprises a solid substrate and at least two thin layers of regular structure applied thereupon, which layers contain at least one amphiphilic compound of the formula (I) R2 R1-, XN-(CH2)1-Y-R^ Z~ (I) R3 in which R1 is H(CH2)nO, H(CH2)nS or H(CH2)n H(CH2)m R2 and R3, independently of one another, H, H(CH2) 0- , H(CH2)_SH<CH2>g * NH(CH2)r·^ are or X is a single bond, -CH=CH-, -N=N-, -CH=N-NH-, or -CH=N-, preferably -CH=CH, -N=N or -CH=N-NH-, is a divalent radical O, NH or S, R* is H, -CO-(CH2)tH, -(CH2)t-H or YR* is -COO, -CONH2, H, OH, -S02(CH2)uH, -CO2(CH2)tH or -CO2(CH2)vOH, Z is at least in part a polyanion, is a number from 1-10, preferably 1-3, n is a number from 10-25, preferably 14-24, m is a number from 0-25, preferably 14-24, p is a number from 10-25, preferably 14-24, g is a number from 10-25, preferably 14-24, r is a number from 0-25, preferably 14-24, t is a number from 0-25, preferably 0-5, in particular 1-5, particularly preferably 1-3, u is a number from 1-20, and v is a number from 2-10, preferably 2-5.

The pyridinum ring can be present at the N end or C end of the radicals -NH-N=CH- and -N=CH-.

The polyanion Z is derived from an acid containing at least 10 acid groups in the molecule. However, the acid compound preferably contains more than 20 acid groups in the molecule, in particular more than 50 acid groups. Examples of inorganic acids supplying polyanions are metaphosphoric acid or polyphosphoric acid. Organic polysulfonic acids, such as polyvinylsulfonic acid and polystyrenesulfonic acid, and polycarboxylic acids, such as polyacrylic acid or polymethacryl ic acid, are preferred. Polycyanoacrylic acid and polyfluoroacrylic acid can also be used. The molecular weight of the polyacid is - 5 not critical, as long as the degree of polymerization is at least 10. It is not required that exclusively the polyanion is opposite to the pyridinium cation in the layer; rather, it is sufficient if at least 50 % of the negative charges required, preferably at least 90 %, are supplied by polyanions; the remainder can be made up by any, in particular water-solubilizing, anions, for example monovalent anions, such as halide, monomethyl sulfate, hydrogen sulfate, perchlorate, nitrate. Acetate and propionate, in particular sulfonates such as toluenesulfonate, increase the solubility of the salts in organic solvents. The corresponding pyridinium salts containing polyanions are in most cases insoluble in water.

The layer elements according to the invention can be produced by dissolving at least one amphiphilic compound of the formula (II) R3 N-(CH^-Y-R4 Z' (II) in which R1 is H(CH2)B0, H(CH2)cS or H(CH2)n.

N20 R2 and R3, independently of one another, are H, H(CH2)pO- , H(CH2)pS- or h(ch2) NH(CH2)r^ t X is a single bond, -CH-CH-, -N=N-, -CH»N-NH-, or -CH-N-, 25 Y is a divalent radical 0, NH or S, R* is H, -CO-(CH2)tH, -(CH2)t-H or - 6 YR* is -COO, -CONH2, H, OH, -SO2(CH2)„H, -C02(CH2)tH or -C02(CH2)v0H, Z' is a solubilizing anion, 1 is a number from 1-10, preferably 1-4, 5 n is a number from 10-25, preferably 14-24, m is a number from 0-25, preferably 14-24, P is a number from 10-25, preferably 14-24, q is a number from 10-25, preferably 14-24, r is a number from 0-25, preferably 14-24, 10 t is a number from 0-25, preferably 0-5, in particular 1-5, u is a number from 1-20, and v is a number from 2-10, preferably 2-5, in a volatile water-immiscible solvent, applying the solution to an air/water phase boundary, the water containing a polyanion Z, compressing the layer remaining after evaporation of the solvent and transferring it to a solid substrate using the Langmuir-Blodgett technique. Preferably, pyridinium salts carrying two alkyl chains having 14 to 24 carbon atoms on R1 (a dialkylamino group) or R1 and R2 (alkoxy and/or alkylthio groups) are employed. The salts of the formula II can also be used together with a second amphiphilic compound. In this case, the proportion of the second amphiphilic compound should be 0-60, preferably 0-10, % by weight. Likewise, layers containing pyridinium salts I can alternate with layers containing molecules of the second amphiphilic compound. This is in particular helpful for ensuring that the molecules of salt (I) are oriented non-centro30 symmetrically.

The hydrophobic portion of the second amphiphilic compound should have a certain minimum length. It is preferred for the second amphiphilic compound to contain at least one hydrophobic portion in which at least 8 carbon atoms are present and at least one polar ether, hydroxyl, carboxyl, carboxylic ester, amino, carboxamido, ammonium salt, sulfate, sulfo, phosphoric acid, phosphonic acid, phosphonic ester, phoephonamido, phosphoric ester or phosphoramido group.

It is particularly preferred for the amphiphilic compound 5 to comprise at least one hydrophobic portion having at least 8 carbon atoms and at least one polar portion selected from the following groups -OR8 -COOR8 R® -N ^R9 XR9 -CO-N COR7 + R8 -N—--R9 ^R10 -so3h -oso3r6 -OPO(OR8) (OR7) -E -O-E -NR8-E, in which R8 to R10, B and E have the following meanings: R8 and R7, independently of one another, are H or CxC3-alkyl, R8, R® and R10, independently of one another, are H, Cx-C^-alkyl, -C2H4OH or -CH2-CHOH-CH3, in particular H or CH3, B is a divalent organic radical such that -NB forms a nitrogen-containing heterocycle, in particular a 5or 6-membered, saturated or unsaturated heterocycle E is in having 1 to 3 carbon atoms or N and 0 atoms or N and S atoms, and ^R11 or -P(0)- R12 ^R11 -P(O) -OR12 which R11 and R12, independently of one another, are -N R For example, the amphiphilic compound can be a fatty acid of the formula CH3(CH2),CO2H, in which g is a number from 8 to 25, preferably 12 to 22.

Advantageously, the second amphiphilic compound used is an unsaturated amide of the formula (III) H - (CH2)a^ - C - C = CH - R14 (HI) H - (CH2>s^ t13 in which R13 is H, Cl, F, CN or (CH2)bH, R1* is H, (CH2)cH or -CH»CH-(CH2)cH, a and s, independently of one another, are a number from 0-22 and b and c, independently of one another, are a number from 0-24, in particular 0-18. a is preferably a number from zero to 18 and s is preferably zero.

The concentration of the polyanion in the aqueous subphase can be selected within wide limits, since only tiny - 9 amounts of polyanion are consumed when the film is transferred. For example, concentrations of lxlO~E to 1.5xl0*2 acid equivalent/L can be used. The solubilizing anion has no effect on the spreading.

In the Langmuir-Blodgett technique, the molecules are compressed by means of a barrier, leading essentially to perpendicular alignment of the alkyl chain relative to the boundary layer in the case of increasing surface density. During the compression, self-organization of the molecules at the boundary layer leads to the formation of a highly ordered monomolecular film whose constant layer thickness is substantially determined by the chain length of the alkyl side chains of the polymers and their tilting angle (the angle by which the molecule chains on the water surface are tilted relative to the normal). The typical thickness of such a film is 2 - 3 nm.

From the dimension of the surface, the spreading volume and the concentration of the solution, the average area per molecule can be calculated. Phase transitions during compression of the molecules can be recognized in the force-area isotherm.

The film is removed from the water surface by immersion or withdrawal of a suitable base material under a constant surface pressure with its order intact.

In most cases, a solution of the polyacid or salts thereof in water serve as subphase for the monofilm production. However, it is also possible to use, instead of water, other liquids having high surface tension, such as, for example, glycerol, glycol, dimethyl sulfoxide, dimethylformamide or acetonitrile, in which the polyacid, but not the pyridinium salt, is soluble as acid or salt.

Suitable base materials are any solid, preferably dimensionally stable, substrates made of various materials. The substrates which serve as base materials for the - 10 films can be, for example, transparent or opaque, electric conductive or insulating.

The substrate can be hydrophobic or hydrophilic. The surface of the substrate to which the LB film is applied, can have been made hydrophobic. The surface of the substrate to be coated should be as clean as possible so as not to interfere with the formation of a thin, ordered layer. In particular the presence of surface-active substances on the surface of the substrate to be coated can impair the formation of a layer. It is possible, before the LB films are applied, initially to provide the surface of the substrate to be coated with an interlayer in order to improve, for example, the adhesion of the film to the substrate.

Materials used for the substrates can be, for example, metals, such as gold, platinum, nickel, palladium, aluminum, chromium, niobium, tantalum, titanium, steel and the like. Other suitable materials for substrates are plastics, such as polyesters, for example polyethylene terephthalate or polybutylene terephthalate, polyvinyl chloride, polyvinylidene chloride, polytetrafluoroethylene, polystyrene, polyethylene or polypropylene.

It is also possible to use semiconductors, such as silicon, germanium or gallium arsenide, or else glass, silicon dioxide, ceramic materials or cellulose products as substrate material. The surface of glass and other hydrophilic substrates can, if necessary, have been made hydrophobic in a conventional manner by reaction with alkylsilanes or hexamethyldisilazane. Which substrate material is chosen depends primarily on the purpose of the layer elements prepared from the film according to the present invention. If the layer elements according to the present invention are used, for example, in electronics or in electrochemical processes, the substrates used are in particular electrically conductive materials, such as metals or metallic surface layers, for example on - 11 plastics sheeting or glass.

The substrates used as base materials for the films according to the present invention may have any desired shape, depending on the intended use. They can be, for example, film-like, sheet-like, plate-like, tape-like or else cylindrical or have any other desired shape. In general, the base materials are flat, planar substrates, such as films, sheets, plates, tapes and the like. The surface of the substrate to be coated is preferably smooth, as is customary for the production of LB films.

In the case of flat, planar substrates, the films according to the present invention can be applied to either or both of the surfaces of the substrate.

The film according to the invention gives a stable multilayer having good nonlinear optical properties and good thermal stability. In a multilayer, it is therefore suitable, for example, for electrooptical switches, diode laser frequency doublers or optical amplifiers.

The layer elements according to the invention can also be used for optical purposes. For these, it is advantageous that the absorption maximum of the LB film can be readily influenced. This is influenced largely by the structure of the group X linked with the pyridinium ring. In the order of single bond < -HOCH- < -N=CH- < -N=N-CH25 < -N=N-, the wavelength of the absorption maximum steadily increases and is eventually shifted to the visible region. For application, the layer elements according to the invention do not have to be colored. It is favorable for frequency doubling of diode laser radiation if no light absorption takes place in the range from 400-800 mm.

In the special case where X is -CH-CH-, the effect of the substituents R1 and (CH2)1-Y-R* on the absorption maximum of the film is evident from Table 1. - 12 The cationic compounds of the formula I are either known or can be easily prepared. Schiff's bases (X is -CH=N-) can be prepared in a known manner from aldehydes and amines. However, they are slowly decomposed in moist air and even faster on a water surface. Synthetic routes for preparing the N-methyl compounds (1=1; YR*=H) where X is -CH=CH (Scheme 1, 2), X = -CH=N-N- (Scheme 3), X = -N=N (Scheme 4) and X = single bond (Scheme 5) are outlined at the end of the description.

In this preparation, the guaternization of the pyridine ring was carried out with methyl iodide (1 « 1; YR* « H). Analogously, guaternization with other reagents, such as 3-bromopropanol, ethyl chloroacetate or 3-bromopropionic acid, is also possible.

It is known (M. Shimomura, K. Fuhjii, P. Karg, W. Frey, E. Sackmann, P. Meller, H. Ringsdorf, Jap. J. Appl. Phys. 27. 1988, L7161-7163) that monolayers composed of cationic amphiphilic compounds without chromophor, such as CH3-(CH2)i7 ®//ch3 Νς Brch3 have improved transfer behavior in the Langmuir-Blodgett technique if polyanions which are derived, for example, from polyvinylsulfonic acid and polystyrenesulfonic acid are present in the aqueous subphase.

Monolayers containing polyanions have improved transfer behavior, higher stability and better alignment of the chromophore than films containing monovalent amines. Good alignment is important for the quality of the frequency doubling obtainable when used in MLO technology. As can be derived from the curve of the frequency doubling intensity as a function of the incident angle, the alignment of the chromophore becomes steeper by about 5’ due to the polyanion. - 13 The invention is illustrated in more detail by the examples which follow.

Example 1 Layer production by the Langmuir-Blodgett method Microscope slides made of glass (76 mm x 26 mm) are cleaned according to the following method: The glass is placed in a freshly prepared mixture of four parts of concentrated H2SO4 and one part of 30 % strength H202 at 60°C for one hour, rinsed with clean water and exposed to ultrasound in a cleaning solution (Extran* AP 11, cone. 2-4 g/1) at 50*C for 15 minutes. It is then again thoroughly rinsed with clean water and dried in a warm air stream. To make it hydrophobic, it is then treated with hexamethyldisilazane vapor (10 minutes at 70’C).

The dye of the formula la mentioned on page 3 is dissolved in methylene chloride. The solution is spread on an aqueous subphase in a Langmuir film balance. The subphases used are pure water and aqueous solutions of polyacrylic acid brought to a pH of 6.0 by adding NaOH in concentrations of 0.01 mg/1 to 1000 mg/1. In the concentration range of 0.1 mg/1 to 100 mg/1, multilayers are produced on a glass substrate by the Langmuir-Blodgett method by transfer: By reducing the monolayer-covered water surface, the surface pressure is adjusted to 30 mN/m and kept constant at this value. The substrate is then immersed vertically downward through the water surface in the film balance (immersion rate: 200 mm/min) and withdrawn again after a brief pause of 10 seconds at the lower reversal point (withdrawal rate: 10 mm/min). A monolayer transfers to the substrate not only during the immersion but also during the withdrawal process. A total of 20 double layers are transferred without difficulty in the presence of the polyanion by repeating the immersion process with a one minute delay each time at the upper reversal point. - 14 The transfer rates are between 80 and 100 %. Using pure water as the eubphase, only 2 double layers obtained with transfer rates below 50 %.

Layers of the pyridinium salts of the formulae can be (lb) (ic) were also prepared by this process. In this process, the subphase temperature was 20 °C and the surface pressure mN/m. Clear, transparent colored multilayers were obtained. The transfer rates are between 80 and 100 %.

Example 2 Measurements of thermal stability Silicon platelets (40 mm x 10 mm) are cut out of a thermally oxidized silicon wafer (thickness of oxide layer: 100 nm) and placed for one hour at 60*C in a freshly prepared mixture of one part of 30 % strength H2O2 and four parts of concentrated sulfuric acid. Following a thorough rinse with clean water, the platelets are treated in an ultrasonic bath with alkaline cleaning liquid (Extran* AP11, cone. 2-4 g/1) for 15 minutes, thoroughly rinsed off with clean water and dried in a warm air stream. They are then made hydrophobic by treating them with hexamethyldisilazane vapor (10 minutes at 70eC).

They are coated with 8 monolayers each of the substances described in Example 1 by the LB technique, using the process described in Example 1. - 15 The coated substrate Is heated in a special apparatus having a linear temperature gradient (0.5’C/sec). During the heating-up, the thickness of the LB layer is measured by means of the intensity of a perpendicularly polarized laser beam (633 nm) reflected by the sample. The temperature at which the first change in the film thickness occurs is 100°C. (For comparison: in LB films made of 22-tricosenoic acid, this temperature is 70’C).

Example 3 Measurements of the critical surface tension Silicon platelets (40 mm x 10 mm) are cleaned by the following method: Treatment in an ultrasonic bath with a mixture of one part of 30 % strength H202 and four parts of concentrated sulfuric acid for one hour, followed by rinsing with clean water. The platelets are then immersed in an HF solution buffered with ammonium fluoride for 20 seconds and then rinsed off with clean water. After this treatment, they are hydrophobic.

The silicon platelets were coated with eight monolayers of the substance la used in Example 1 by the method described there (polyacrylic acid concentration in the subphase 10 mg/L).

Droplets of a number of liquid n-alkanes (CgH20 - CieH34) are applied to the surfaces of the transferred layers, and the contact angles of the droplets with the surface are measured. These contact angles are used to determine the critical surface tension by the method of Zisman.

In this example, it is 20-22 mN/m.

(For comparison: In the case of a polyethylene surface, this measurement gives a value of 31 mN/m). - 16 Example 4 Determination of the nonlinear optical properties Microscope elides made of glass (76 x 26 mm) were cleaned by the method described in Example 2, omitting the step of making them hydrophobic. The microscope slides thus treated were then hydrophilic. The substrates were immersed in a Langmuir film balance in subphases comprising aqueous solutions of polyacrylic acid (1 mg/1 and 5 mg/1), the substances described in Example 1 were spread on the water surface, compressed, and the glass slides were withdrawn from the subphase at a surface pressure of 30 mN/m and a rate of 1 cm/min at 20°C. In this manner, one monolayer was transferred to the glass slide.

The value of the 2nd order susceptibility χ (2) was measured by the method of optical frequency doubling, using the following experimental set-up: An Nd-YAG laser generates a pulsed laser beam (pulse duration about 30 ps) having a wavelength of 1064 nm (w = 9398 cm'1), which is divided by a beam divider into a reference beam and a test beam. The reference beam is converted by frequency doubling in a reference sample comprising a polycrystalline powder of an organic compound having a high χ (2) into a reference harmonic beam having a wavelength of 532 nm, its intensity being measured by a photodetector. The sample beam irradiates the Langmuir-Blodgett monolayer transferred to one side of the glass slide and being mounted on a rotating stage perpendicular to the optical plane. The sample is rotated by the incident angle. The frequency-doubled beam is measured by a photodetector, its intensity is standardized by reference to the reference signal, and the intensity of the harmonic is measured as a function of the incident angle. The intensity of the sample is then calibrated by comparison with the harmonic of a calibrated quartz plate. The nonlinearity (χ (2)) and the - 17 average orientation of the chromophore (tilting angle with respect to the normal of the substrate) can be determined from the magnitude and angle dependence of the intensity of the harmonic. The following values were found for non-linearity: Concentration of polyacrylic acid mg/L 1 5 (2) Tilting angle 250 pm/V 32* 270 27’ 205 27“ (For comparison: The susceptibility of the compound LiNbO3 used commercially in the form of crystals is about 8 pm/V).

Example 5 (Comparative Example) A microscope slide made of glass is cleaned as in Example 1 and made hydrophobic. Dye Ia is spread on an aqueous subphase from a solution in methylene chloride (concentration : 1 mg/ml). The subphases used are aqueous solutions of citric acid, oxalic acid and sulfuric acid in a concentration of 5 mg/1, which have been brought to a pH of 7 by adding NaOH. The coating experiments by the Langmuir-Blodgett method were carried out as described in Example 1. The test results are listed in the table below: Subphase: Citric acid Oxalic acid Sulfuric acid Subphase temp.: Surface 10, 20’C 20*C 20*C 5 pressure: 30 mN/m 20, 30 mN/m 30 mN/m Transfer Transfer of beh.: Transfer of 3 monolayers Transfer of 3 monolayers with trans- 4 monolayers with trans- fer rates with trans- 10 fer rates below 50 % fer rates below 50 % below 50 % Example 6 Synthesis of dye la Quaternization of 4-picoline using methyl iodide 15 4.85 ml (4.66 g, 50 mmol) of 4-picoline are initially introduced at 20°C into a glass flask , and 3.11 ml (7.1 g, 50 mmol) of methyl iodide are carefully metered in with cooling. After the addition is complete, the solid formed is taken up in 80 ml of dry acetone and refluxed for one hour. The mixture is then allowed to crystallize completely in a freezer, and the product is recrystallized again from ethanol, to give 5.99 g (25.5 mmol, 51 %) of a white powder.

^-NMR (100 MHz, CDC13) : 6 « 2.70 (s, 3H, -CH3); 4.65 (S, 3H, N-CH3); 7.75-7.95 (d, 2H, aromat. H); 9.1-9.3 (d, 2H, aromat. H) Alkylation of aniline with 1-bromohexadecane 23.3 g (0.25 mol) of freshly distilled aniline and 168 g (0.55 mol) of 1-bromohexadecane are stirred in a one-neck flask equipped with reflux condenser under an argon atmosphere at 90eC for 3 days. After cooling, 0.7 1 of toluene is added, and the solution is extracted with a 10 % strength aqueous solution of Na2CO3. After extraction - 19 with a 5 % strength aqueous HCl solution, the hydrochloride precipitates and is filtered off through a nutsch filter. The free base is then liberated by adding 10 % strength Na2CO3, 0.7 1 of toluene is added, the organic phase is separated off and dried with Na2S04, and the solvent is removed in vacuo. Finally the product is recrystallized two more times from 1.5 1 of ethanol each time, to give 56.4 g (0.1 mol, 42 %) of a white powder which melts between 47.5 and 49 *C.

XH-NMR (100 MHz, CDC13) ί 6 - 0.7-1.0 (t, 6H, -CH3); 1.11.4 (m, 56H, -CH2-alkyl); 3.1-3.3 (t, 4H, N-CH2); 6.5-6.8, 7.0-7.3 (m, 5H, aromat. H) Vilsmeier formylation of Ν,Ν-dihexadecylaniline g (18.5 mmol) of Ν,Ν-dihexadecylaniline are made into a paste with 75 ml of dry dimethylformamide, which is cooled to 5*C, and over a period of 5 minutes 2.8 g (18.5 mmol) of freshly distilled POC13 are added. The mixture is then allowed to warm to 20*C, stirred at this temperature for one hour and heated at 80°C for 3 hours.

After cooling of the reaction solution, the reaction mixture is decomposed with 40 g of ice water and neutralized with about 10 ml of 5 molar NaOH solution. The precipitate formed is filtered off with suction and recrystallized from ethanol to give 4.71 g (8.3 mmol, 45 %) of a cream-colored powder. 1H-NMR (100 MHz, CDC13): δ * 0.7-1.0 (t, 6H, -CH3); 1.11.4 (m, 56H, -CH2-alkyl); 3.15-3.4 (t, 4H,N-CH2); 6.7-6.9 (d, 2H, aromat. H); 7.65-7.85 (d, 2H, aromat. H); 9.75 (s, 1H, CHO) Reaction of 4-[Ν,Ν-dihexadecyl]aminobenzaldehyde with N-methyl-4-picolinium iodide 0.94 g (4 mmol) of N-methyl-4-picolinium bromide, 2.28 g (4 mmol) of 4-[Ν,Ν-dihexadecyl]aminobenzaldehyde and - 20 1.5 ml of piperidine are suspended in 150 ml of ethanol, and the mixture is refluxed for 3 hours. After cooling, the mixture is allowed to complete crystallization in a freezer. The crude product is purified by column chrom5 atography on silica gel Si 60 (eluent: CH2C12/CH3OH 20:1). 1.5 g (1.9 mmol, 48 %) of a red powder are obtained which melts at temperatures above 200C with decomposition.

XH-NMR (100 MHz, CDC13),· S - 0.7-1.0 (t, 6H, -CH3); 1.11.4 (m, 56H, -CH2-alkyl); 3.15-3.4 (t, 4H, N-CH2); 4.3 (s, 3H, N-CH3); 7.1 (m, 6H, aromat. H); 8.65 (m, 2H, aromat. H) Table 1 Structural formula Absorption in the LB film AUI/nm CH3-(CH2)23 y CH3-(CH2)15 475 Br CH3-(CH2)15 s ch3.(ch2)15 n+-ch2-ch2-oh Br' 460 Ch3-(Ch2)15 y CH3-(CH2)15 n+-ch2-coo-ch3 470 Br CH3-(CH2)l5 CH3-(CH2)i5 CH3-(CH2)i5 CH3-(CH2)x5 475 460 CH3-(CH2)17 I 380 - 22 Scheme 1 Synthetic route: Γ Synthetic route: HO CH3-(CH2)l; -° ,θ CH3-(CH2)I7 CH3-(CH2)17 -0 H3C-^Ai+CH, Piperidine ch3-(ch2)17 ch3-(ch2)17 ch3-(ch2)17 - 24 Scheme 3 CH3-(CH2)17 —0, I* Synthetic route: - 25 Scheme 4 CH3-(CH2)15 ch3-(CH2)15 Br Synthetic route: CH3-(CH2)j5 \ /“λ / \=/ CH3-(CH2)15 CH3-(CH2)15 CH3-(CH2)15 CH3-(CH2)15 ch3-(ch2)15 Scheme 5 CH3-(CH2)17 CH3-(CH2)17 Synthetic route: LiAlH, CH3-(CH,) ch,-(ch2)16-coci CH3-(CH2)17 s N< LiAlH, 2-Ί6 // CH,-(CH2)17 x _ N—(' CH3-(CH2)17 CHjBr --> CH3-(CB2)17 CH,-(CH2)i7

Claims

1. Is a number from 1-10, 3, n is a number from 10-25, m is a number from 0-25, p is a number from 10-25, q is a number from 10-25, r is a number from 0-25, t is a number from 0-25, - 28 u is a number from 1-20, and v is a number from 2-10. HOE 89/F 390

1. A layer element comprising a solid substrate and at least two thin layers of regular structure applied thereupon, which layers contain at least one amphiphilic compound of the formula (I) R 3 in which R 1 H(CH,kO, H< CH 2>n S or N10 R 2 and R 3 * , independently of one another, H, H(CH 2 ) 0-, H( CH 2>gv H(CH 2 ) r X H(CH 2 ) pS are or X is a single bond, -CH=CH-, -N«N-, -CH=N-NH-, or -CH-N-, Y is a divalent radical O, NH or S, R* is -H, -CO-(CH 2 ) t H, -(CH 2 ) t -H or YR* is -COO', -CONH 2 , H, OH, -SO 2 (CH 2 )„H, -CO 2 (CH 2 ) t H or -CO 2 (CH 2 ) V OH, Z is at least in part a polyanion,

2. A layer element as claimed in claim 1, wherein R 1 in the amphiphilic compound of the formula I is H < CH 2>n H(CH 2 ) Nwhere n is 14-24, m is 14-24 and R 2 and R 3 are H or R 1 and R 2 , independently of one another, are H(CH 2 ) n -0 or H(CH 2 ) b -S where n is 14-24, m is 14-24 and R is H.

3. A layer element as claimed in claim 1, wherein the molecules of the formula I in the layers are essentially oriented uniformly and non-centrosymmetrically.

4. A layer element as claimed in claim 1 or 2, wherein each layer containing or comprising the compound of the formula (I) alternates with a layer containing or comprising a different amphiphilic compound. 20

5. A process for preparing a layer element as claimed in claim 1, which comprises dissolving at least one amphiphilic compound of the formula I in which Z is a solubilizing anion in a volatile water-immiscible solvent, applying the solution to the boundary layer of water, containing a polyanion, and air, compressing the layer remaining after evaporation of the

6. 6.

7. 7.

8. 8.

9. 9.

10.

11. 10. 11. solvent and transferring it to a solid base material using the Langmuir-Blodgett technique. The process as claimed in claim 5, wherein the spreading is carried out on the surface of water containing polyacrylic acid. The process as claimed -in claim 5, wherein the spreading is carried out on the surface of water containing polyeulionic acid. The process as claimed in claim 6 or 7, wherein the polyacid concentration is 0.1 mg - 1 g per 1 of water. A layer element as claimed in claim 1, substantially as hereinbefore described and exemplified. A process as claimed in claim 5, substantially as hereinbefore described and exemplified. A layer element as claimed in claim 1, whenever prepared by a process claimed in a preceding claim.