CA2031786A1 - Layer element and processes for its production - Google Patents

Abstract

Abstract of the Disclosure HOE 89/F 390 Layer element and a process for its preparation A layer element usable for NLO purposes can be prepared by the Langmuir-Blodgett technique. It comprises a solid substrate and at least two thin layers of regular struc-ture applied thereupon, which layers contain at least one amphiphilic compound of the formula (I) Z- (I) in which R1 is H(CH2)nO, H(CH2)nS or , R2 and R3, independently of one another, are H, H(CH2)pO-, H(CH2)pS- 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, R4 is -H, -CO-(CH2)tH, -(CH2)t-H
or YR4 is -COO-, -CONH2, H, OH, SO2(CH2)uH, -COz(CH2)tH or -CO2(CH2)vOH, Z is at least in part a polyanion, 1 is a number from 1-10, 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, u is a number from 1-20, and v is a number from 2-10.

Description

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HOECHST ARTIENGESELLSCH~ HO~ 89/F 390 D.Ch.SY/Le Description L~yer element and proce~ses for its production The present invention relateg to a ~ilm applied to a substrate, which film comprise8 at lea8t 2 monomolecular amphiphilic pyridinium layers st~bilized by a polyanion.

Nonlinear optic8 (NLO) i~ of grea~ import~nce for the future development of information technology, due to lts p~tential for-rapid ~ignal proca~8ing and tr~nsfer and for new metho~ in data processing. Specific organic compounds have higher efficiencies and ~horter ~witching times than the co~v~ntional inorganic ~ub~t~nces for nonlinear optics.

A substance has nonlinear optical properties i~ the polariza~ion P, which is generated by the in~eraction between the substance and a trong electric iield (a laser beam or a strong direct vol~age field)l depends on the higher power~ of the field ~reng~h, according to ~he following equation:

x(l) El ~ X(2) : ~1E2 ~ X(3) : ElE2E3 ~ ' X (1), x (2) and x (3) ~re the susceptibilitiQ~ of the 1st, 2nd and 3rd order. ~ i8 the electric field which ~an contain component~ of ~everaI freguen~ies. ~LO intQrac-tion~ can give rise to field~ with n0w frequencie~ and can change the re~ractive indice~ of the material.
Su~ceptibilities x (2) ~nd X (3) depend on the molecular hypexpolarizabilities ~ and 7.

Important nonlinear optical effect~ depending on X (2) are doubling of the frequency of a light beam, in par-ticular a laser beam, parametric reinforcement of a ~eakligh~ signal and elec~rooptical conver~ion of elec~ri~

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siynals. To obtain 2nd order ef feot8, ~he active mole-cules have to be aligned non-centro6ymmetrically, since for centro3ymmetrical ~ubstances x (2) i8 zero.

One process which enable~ the production of films having a particularly favorable alignment for NLO i~ the Langmuir-Blodgett (LB3 process. In thi~ process, mole-cules are spread on a water ~urface, aligned in parallel by reducing the area per molecule and applied to a substrate by immer~ion and withdrawal of a base ~aterial at a constant surface pres~ure. In ~ach immersion opera-tion, one monomolecular layer i~ transferred with it8 order intact. Amphiphilic molecules, i.e. molecules having a hydrophilic end (a Nhead~') and a hydrophoblc end (a "tail") are used for building up the LB layers~
Nultilayers for use in optical structural components require repeated immer ion operations.

To obtain LB layer~ having high 2~d order susceptibilities, organic compounds having not only high molecular 2nd order hyperpolarizabilitie~ ~ but also amphiphilic properties are used as the ~tarting material.
A compound has a large ~ value if i~ ~ontain~ a con-~ugated electron system (for example a benzene ring) in which one or more electron donor groups ~nd one or more electron acceptor groups are incorporated. A hydrophobic group is incorporated at the do~or or ac~eptor end. The hyperpolarizability is increased if the ~olecule a~sorbs light in the wavelength range of the irradiating electric field or the field produced by the ~LO (so-c~lled r~son-ance amplification). ~owever, ab80~ptiora8 are undesirable in many applications sin~e they give rise to lo~&e~ and have an adverse ef~ect on optical ~tability (l~vel of light intensity which i8 toleratad withou~ ~ny permanent material defects~. An ideal co~pound i~ on~ ~hich ha~
high hyperpolarizability without havin~ ~trong ~b~orption in the desired wavelength range.

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It was already known that the pyridinium compound of the formula Ia - (CH3(CH2)15)2 N ~ ~CH=CH- ~ N+-C~3 and similar compounds have very good ~L0 proper~ie~ in monolayers (Lupo et al., J. Opt. Soc. Amer., B 5 r 500 (1988)). Using these pyridinium compounds or similar dyes containing monovalent anions, it i~ usually no~ pos6ible to apply more than o~e double layer; further $mm2r8ion operations do not result in further ~ra~sfer of ~he dye.
Moreover, the dye layers co~prising monovalent anions are u~ually stable only up to 70C.

~he object was therefore to ~tabilize a film composed of amphiphilic pyridinium compounds in such a manner that several monolayers can be transferred ~n 6ucce8 ion with the formation of multilayers. ~t the 8~me time, ghe thermal ~tability (compared with the known film~) ~hould be improved, if possible. `!

A layer element has now been found which compri~es a solid substrate and at 18a8t two thin layers of regular structure applied thereupon, which laysr~ contain at least one amphiphilic compound of the form~la (I) Rl_~X_~N-(C}1231-Y-R4 Z tI) in which R1 is X(CHz)nO, H(C~2)nS or H(CH2)n~
N- :
~(CH2)~ ~

R2 and R3, independen~ly of one ~nother, are (C~() 2)p ~(CH2~pS

~(CH2)r t X is a ~ingle bond, -CH=CH-, -N=N-, -C~aN-NH-, or -CH=N~, S pxeferably ~CH=CH, -N=~ or -CH=N-N~-, Y is a divalent radical O, NH or S, R4 iB ~, -CO-(CH2)tH, -(C~2~t-H
or YR~ is -CCO , -CONH2, H, OH, -S02(CH2)~H, C02(CH2)t~ or --CO2(CH2)~.0H~
Z is at least in part a polyanion, 1 is a number from 1-10, preferably 1-3, n is a number from 10-25, preferably 14 24S
m is a number from 0-25, prefer~bly 14-~4 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, t is a number from 0025, preferably 0-5, in particular 1-5, particularly preferably 1-3, u i~ a number from 1-20, and V i8 a number ~rom 2-10, pre~erably 2-S.

The pyridinum ring can be p~e~ent a~ ~he N end or C ~nd o~ the radicals -NH-N=CH- and -N=CH-.

The polyanion Z i8 derived from an acid con~ai~ing at lea6t 10 acid group6 in the molecule. However, the acid compound preferably contains more than 20 ~cid graup~ in the molecule, in particular more than 50 acid ~roups.
Examples af inorganic acids ~upplying polyanion~ ~re metapho~phoric acid or polyphosphorlc ~cid. Organic :~
polysulfonic acids, such a~ poly~inylsulfonic acid and polystyrenesulfonic acid, and poIycarboxylic acids, ~uch as poIyacrylic acid or polymethacrylic acld, are pr~-ferred. Polycyanoacrylic acid and polyfluoroacrylic acid can also be u~ed. The molecul~r weight of the pDly~cid i8 `` ~ `; , ~ .......... - ; : ; .

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not critical, as long as the degree of polymexization i~
at least 10. It i~ no~ required tha~ e~Eclusively the polyanion is opposite to the pyridinium cation in the layer; rather, it i8 su~ ient ~.f at least 50 % of the negative chaxges required, preferably at least 90 %, are supplied by polyanions; the remainder can be made up by any, in particular water-~olubilizing, anions, for ~xample monovalent anions, ~uch a3 halide, monomethyl 8Ul f ate, hydrogen l3ul f ate, perchlorate, nitrate . ~cetate and propionate, in par~icular sulfonates such a~ tol-uenesulfonate, increase the ~olubility of the ~alt~ in organic solvent~. ~rhe ~:orresponding pyridinium xalts containing polyanions are in mos~ ~ases insoluble in water.

The layer elem~nts a~cording to the invention can be produced by dis601ving at least ons amphiphilic compound o~ the formula (II) R

Rl- ~ X- ~ N-(CH2)1-Y-R4 zl- (II) R

in which Rl ia H(CH2)30, H(CH2)~,S or HlCH2)n~
N-H(CH2)m R2 and R3, indep~ndently of o~e another, ~re H, H(CH2)pO- , H(CH21pS- or H(CH23g ~ N-H(CH2)r~
~ i8 a ingle boTId~ -CHSCH-, --N-N-, --CH=N~ , or -CH=N-, Y is a^divalent radical O, N~ or S, Ri iB H, -CO-~CH2)tH, -(C~)t-H
or . .
, . , . ~ . ~ . :
.

. - ~ . . . .
.. ~ . . .
- , r~ ~ ~

YR4 is -COO~, -CONH2, H, OH, -S02(CH2)~H, -C02~CH2)~H or -CO;!(CH2)~,OH, Z' is a solubilizing anion, 1 is a number from 1 10, preferably 1-4, n is a number from 10-25, preferably 14-24, m is a number from 0 25, preferably 14-24, p i6 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, t is a number from 0-25, preferably 0 5, in particular 1-5, u is a number ~rom 1-20, and v is a number ~rom 2-10, preferably 2- 5, in a volatile water-~mmiscible ~olvent, applyins the solution to an air/water phase boundary, the wa er con-taining a polyanion Z~~ compre6sing ~he layer remaining after evaporation of the solvent and transferring it to a solid substrate using the Langmuir-Blodgett tech~que.
Preferably, pyridinium salt~ carrying t~o alkyl chains having 14 to 24 carbon atoms on R1 (a dialkylamino group) or Rl and R2 (alkoxy and/or alkylthio group~) are employed. The 8alt8 of the ~ormula II can al30 be U8ed together with a second amphiphilic compound. In thi~
case, the proportion of the second amphiphilic compound should be 0-60, preferably 0-10, % by weight. ~ikewi~e, layers containing pyridinium 8alt8 I can alternate with layers containing mol~cules of the ~econd am~hiphilic compound. This is in particular helpful ~or en~urin~ that the molecules o~ salt (I) are oriented non-ce~tro-symmetrically.

The hydrophobic portion of the ~e~ond amphiphilic com-pound ~hould have a certain minimum length. I~ i~ pre-ferred for the second amphiphilic compound to contain at least one hydrophobic portion in wh~ch at laast 8 carbon atoms are present and at lea~t one polar e~her, hydro~yl, carboxyl, carboxylic ester, amino, carboxamido, ~mmonium .

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salt, sulfa~e, sulfo, phosphori~ acid, phosphonic acid, phosphonic ester, pho~phonamidot phosphoric ester or phosphoramido group.

It is particularly preferred for the amphiphilic compound to comprise a~ least one hydrophobi~ por~ion having at leas~ 8 carbon atoms and at lea~t one polar portion selected from the following groups _oR8 -CooR5 ~R8 ~ R9 ~R8 -CO-N
\~?.9 - ~ coR7 .

~ R8 ~RlO

-oSo3R3 opo(oR6~ (oR7) -E
-O-E
-NR3-E~
in which R6 to Rl, B ~nd E have the following ~ea~in~:
R3 and R7, independently of one another, are H or Cl-C3-all~rl, R8, R~ and RlD, independently of one ~no~her, are ~
Cl-Cj-alkyl, -C2H40H or -CH2-CHOH-CH3, in particular H
or CH3, B is a divalent organi~ radical ~uch that -NB form~ a nitrogen-con~aining he~erosycler in paxticular a 5-or 6-membered, saturated or un~a~urated heterocy~le ' . ~ . . ' ' ':' 2~3 - a -having 1 to 3 carbon atoms or ~ and O atom~ or ~ and S atom~, ~nd E is Rll or _p(o) .. _ R12 ",R
-P(O) - --OR12 in which R11 and R12, independently of one another, are -N~

For xample, the Emphiphilic compound can be a fatty acid of the formula CH3(C~2~CO2H, in which g i~ a number from 8 to 25, preferably 12 to 22.

Advantageously, the second amphiphilic co~pound used is an unsaturated amide of the formula (III) H - (CH2)a ~ N - ~ _ r = CH _ R14 (III) H - ~CH2)S ~ 8 ~13 in which R19 i~ H, Cl, F, CN or (C~2)~H-R14 is H, (C~2)CH or -CH~CH-(CH2)o~

a ~nd ~, independantly of one anothex, are a numbex from 0 - 22 and b and c, independently.o~ one another, are a n~mber from 0 - 24, in particular 0 - 18.
a is preferably a number fro~ ~ero~to 18 and ~ i8 prefer- :
ably zero.
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The concentration of the polyanion in the aqueous ub-phase oan be selected with1n`wid~ its~ ince only t~ny ~;

. , - . . . . . - .
, - . : - , . . . . .

2~3~ 3 g _ amounts of polyanion are con~umed when the film i~
transferred. For example, concentrations of lxlO~ to 1.5xl0-2 acid equivalent/L can be used. The ~olubilizing anion has no effec~ on the ~preading.

S In the Langmuir-Blodgett technique, the molecule~ are compressed by means of a barrier, leading essen~ially to perpendicular alig~ment of the alkyl chain relative to the boundary layer ~n the ca~e of increa~ing 3uxface density. During the comprQssion, self-organization of the molecules at the boundary layer lea~s ~o the forma~ion of a highly ordered monomolecular film whose constant layer thickness is ~ubs~antially determined by the chain length of the alkyl ide chains of ~he polymers and thsir tilting angle (the angle by which the molecule chains on the water surface are tilted relative to the normal). The typical thickne~s of ~uch a film i~ 2 - 3 nm.

From the dimension of the surface, the ~preading volume and the concentration of the ~olution, the average area per molecule can be calculated. Phase tran~itions during compression of the molecules can be recogni2ed in the force-area isotherm.

The film i~ removed from the water surface by immsr~ion or withdrawal of a suitable base material under a c~n-stant surface prassure with it~ order intact.

25 In most cases, a ~olution of the polyacid or 8alt5 thereof in water ~erve as subphase for the mono~ilm production. However, it i~ al80 possible to u~e, instead of water, other liquids having high ~urface ten~ion, such as, for example, glycerol, glycol, dimethyl ~U1fQXidet dimethylformamide or acetonitrile, in which the polyacid, but not ~he pyridinium salt, i~ ~oluble as acid or ~al~.

Suitable base materials are any solid, preferably dimen-~ionally stable, substrates made of v3riou~ materials.
The substrate6 which ~erve as base materials fQr the ~,~3~

films can be, for example, transparent or opague, elec-tric conductive or in~ulating.

The substra~e can be hydrophobic or hydrvphilic. The surface of the sub ~ra~e to which the LB film i~ applied, 5 can have been made hydrophobic. The ~ur~ace of ~he substrate to ~e coated ghould ~e as ~lean aa po~slble 80 as not to inter~ere wi~h the formation o~ a thin, ordered layer. In particular ~he presen~e of ~urface-active substances on the ~urface of the gubstrate ~o be coated can impair the formation o~ a layer. It $3 possiblet before the LB films are appliRd, in~tially to provide the ~urface of the ~ubstrate to be coated with an in~erlayer in order to impro~e, for example, the adhesion of the film to the ~ubstrate.

Materials u6ed for the ~ub trates can be, for example~
metals, such as gold, platinum, nickel, palladium, aluminum, chromium, niobium, ~antalum, ti~anium, ~teel and the like. Other suitable material~ for ~ubstra~ss are-plastics, such as polyes~ers, for example polyethylene ~Q terephthalate or polybutylene ~erephthalate, polyvinyl chloride, polyvinylidene chloride, polytetrafluoro-ethylene, polystyrene, polyethylene or polypropyl~ne.

It is al80 possible to use ~emiconductors, such BS
silicon, germanium or gallium ar~enide, or el~e glas~, ~5 silicon dioxide, ceramic matexlal~ or callulo~e products as ~ubstrate material. Tha surface of glass and other hydrophilic ~ubstrates can, if necessary, have been made hydrophobic in a conventional manner by reaction with alXyl~ilanes or hexamethyldisilazane. Which ~u~strate material is chosen depends primarily on the purpo~e of the layer element~ prepared from the film according to the present in~ention. If the layer elements accvrding to the present inYention are used, for *xample, in electron-ics or in electrochemical processes, the substrates uRed 3S are in particular electrieally conductive materials, such as metals or metallic aurface l~yer~, for ex~mple on ' ' ' ~. .

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plastics sheeting or glass.

The substrates used as base materials ~or the films according ~o the present invention may have any desired shape, depending on the in~ended use. They can be, for example, film-like, sheet-like, plate-like, tape-like or else cylindrical or have any o~her desired shape. In general, the base material~ are ~lat, planar substrates, such as films, fiheet~, plates, taps~ and ~he like. The surface of the sub~trate to be coate~ i8 preferably smooth, as is customary for the produc~ion of LB films.
In the case of flat, planar ~ub~tra~es, the film~ accord-ing to the present invention can be applied ~o either or both of the surfaces of the ~ubstrate.

The film according to the invention gives a st~ble multilayer having good nonlinear optical properties and good thermal stability. In a multilayer, it is therefore suitable, for example, for elec~rooptical switche~, diode laser frequency doublers or optical amplifiers.

The layer elements according to the invention can ~1BO be used for optical purposes. For these, it is advantageous that the absorption maximum of the LB film can be readily in~luenced. Thi~ i~ lnfluenced largely by the ~ruzture of the group X linked with the pyridinium ring. In the order of 6ingle bond < -HC-CH- < -N-CH- ~ -N=N-C~-< -N=N-, the wavelength of the ab~orption maximum steadily increa~es ~nd i~ eventually shifted to the visible region. Por appl~cation, ~he layer elements according to the in~ention do not have to be colcred. It i8 favorable for frequency doubli~g of diode laser radiation if no light absorption takes place in the range from 400-800 mm.

In the special case where X i8 -CH=C~-, the effec~ of ~he substituents R1 and (CH2)l-Y-R~ on the absorption ma~imum of the film is evident from Table 1.

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~he cationic compounds of the formula I are either known or can be easily prepared. Schif~s base~ (~ is -CH=N-) can be prepared in a known manner from aldehydes and amines. However, they are slowly decomposed in moi~t air and even faster on 8 water ~urface. Synthetic routes for preparing the N-methyl compounds ~ ; YR4=H) where ~ is -CH=CH ~Scheme 1, 2), X = C~=N-N- (Scheme 3), ~ = -N=N
(Scheme 4) and X = single bond (Scheme 5) are outlined at the end of the description.

In this preparation, the quaternization of tha pyridine ring was carried out with methyl iodide (1 = 1; YR4 = H).
Analogously, quaternization with other reagents, ~uch as 3-bromopropanol, ethyl chloroacetate or 3-bromopropionic acid, is also possible.

It is known (M. Shimomura, R. Fuh~ii, P. Rarg, W. Frey, E. Sackmann, P. Meller, H. Ringsdorf, Jap. J. ~ppl. Phys.
27, 1988, L7161-7163) that monolayers composed of cat-ionic amphiphilic compounds without chromophor, ~uch a~
CH3-(CH2)17 ~ ~ 3 ~ Br~
CH3-(~H2)17 3 have improved transfer behavior in the Langmuir-Blodgett technique if polyanion~ ~hich are derived, for example, from polyvinylsulfoni~ acid and poly~tyrenesulfonic a~id are present in the aqueous subphase.

Monolayer~ containing polyanion~ have improved tran~fer behavior, higher ~tability and bett~r ali~nment of the chromophors than $ilms containing ~onovalent amines. Good alignment i8 i~portant for the quality of the freguency doubling obtainable when used in NLO technology. A~ can be derived from the curve of the freguency doubl~ng intensity as a function of the lncident angle, the alignment of the chromophors becomes "~teeper" by about 5 due to the polyanion.

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The invention is illu~rated in more detail by the examples which follow.

lS~ample 1 Layer production by the Langmuir-Blodgett method S Microscope slides made of glass (76 mm x 26 mm) are cleaned according to the following met~od: ~he gla~ i8 placed in a freshly prepared mixture of four parts of concentrated H2S04 and one part of 30 % strength ~22 at 60C for one hour, rinsed with clean water and e~po~ed to ultrasound in a cleaning ~olution (~x~ran ~P 11, eonc.
2-4 g/l) at 50C for 15 minutes. ~t i8 ~hen ~gain thoroughly rinsed with ~lean wa~er and dried in a warm air stream. To make it hydrophobic, it i~ ~hen treated with hexamethyldi~ilazane vapor (10 minute6 at 70C).

The dye of the formula Ia mentioned on page 3 is dis-solved in methylene chloride. The ~olution i8 ~pread on an aqueous subphase in a ~angmuir film balance. ~he subphases used are pure water and aqueous ~olution~ of polyacrylic acid brought to a pH of 6.0 by adding ~aOH in concentrations of 0.01 m~/l to 1000 mg/l. In the ~cncen-tration range of 0.1 mg~l to 100 mg~ ultilayer~ ~re produced on a glass sub~trate by the Lan~muir-Blodgett method by transfer:

By reducing the monolayer-covered wa~er ~urfa~e, the surface pressure is ad~usted to 30 mN/m and kept constant at this value. The ~ub~trate i8 ~hen immer~ed vertically downward through the water ~urface in ~he film balance (immersion rate: 200 mm/min) and withdrawn ~g~in ~fter a brief pause of 10 seconds at the lower re~ersal poin~
(withdrawal rate: 10 mm/min). ~ monolayer ~ransfer6 $o the substrate not only durin~ the immer~ion bu~ also during the withdrawal proce~s. A to~al of 20 double layers are transferred without diffiGulty in the presence of the poly~nion by repeating the immersion proce~s with a one minute delay each time at the upper rever~al point.

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~rhe transfer rate~ are between 80 and 100 %. U~ing pure water as the ~ubphase, only 2 double layer~ can be obtained with ~ransfer rates below 50 %.

Layer~ of the pyridinium ~alts of the formulae (Ib) C16H330- ~ -CH=C~- ~ N-CH3 I-and (cH3tcH2)l~)2 N ~ -CH=CH ~ N-CH2C~2H (Ic) were also prepared by this process. In this proce~s~ the subphase temperature wa~ 20C and ~he surface pressure 30 mN/m. Clear, trans~arent colored multilayers ~ere obtained. The transfer rates are between 80 and lO0 ~.

E~ample 2 Measurements of thermal ~tability Silicon platelet~ (40 mm x 10 mm) are cut out of a thermally oxidized silicon wafer ~thickne~s of oxide layer: lO0 nm) and placed for one hour at 60C in a freshly prepared mixture of one part o~ 30 ~ s~rength H202 and four parts of concentra~ed fiulfuric acid. ~ollowing a thorough rin~e with clean water, the platel~ts ~re treated in an ultraso~ic bath with alkRline ~lea~ing liquid (Extran ~Pll, conc. 2-~ gll) ~or 15 ~inute~, thoroughly rinsed off with clean wa~er and dried in a warm air ~tream. The~ ~re then made hydrophoblc by - treating them ~ith hexamethyldi~ilazane vapor (lO mlnute~
2S at 70C).

They are coated with 8 monolayer~ each of the ~ubhtances described in Example l by the LB technique, using the process described ln ~xample 1.

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The coated subs~rate is heated in a ~pecial apparatus having a linear temperature gradient (0.5C/~ec). DNring the heating-up, the thickness of the ~B layer i~ measured by means of ~he intensity of a perpendicularly polarized laser beam (633 nm) reflectQd by he sample. The temperature at which the first change in the fi~ thick-ness occurs i8 100C. (For compari~on: in ~B f~lm3 made of 22-tricosenoic acidl this temperature 1~ 70'C).

~ample 3 Measurement~ of the cri~ical ~urface tension Silicon platelets (40 mm x 10 mm) are cleaned by th0 following method: Treatmen~ in an ultrasonic bath with a mixture of one part of 30 ~ strength H2O2 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 wi~h ammonium fluoride for 20 seconds and then rinsed off with clean water. After this treatment, they are hydrophobic.

The silicon platelet~ were coated with eight monolayers of the substance Ia u~ed in Example 1 by the method described there (polyacrylic acid concQntration in the subphase 10 mg/L).

~roplets of a number of liquid n-alkane~ ~C~H~o - Cl~H34) are applied to the surfaces o~ the tran~ferrad layer3, and the contact angles of the droplets with the ~urface are measured. ~hese contact ~ngle~ are u~ed to determine the critical ~urface tension ~y the m~thod of ~i~man.

In this example, it is 20~22 ~N/~.
(For comparison: In the ca~e of ~ polyethylene surface, this measurement gives a value of 31 mN/m).

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X~ample 4 Determination of the nonlinear optical properties Microscope filides made of gla~s (76 x 26 mm) were cleaned by th~ method described in Example 2, omitting the step of making them hydrophobic. ~he ~icroscope ~lide~ thus treated were then hydrophilic. The substrates were immersed in a Langmuir film balance in subphases compris-ing aqueou~ ~olution~ of polyacrylic acid (~ mg/l and 5 mg/l), the su~stance~ de~cribed in Example 1 were spread on ~he wa~er ~ur~ace, compres3ed, and the glass slides were withdrawn from the ~ubphase at a ~urface pressure of 30 mN/m and a rate of 1 cm/min at 20C. In this manner, one monolayer was transferred to the gla~s slide.

The value of the 2nd order ~usceptibility x (2) was measured by the method of optical frequency doubling, using the following e~perimental set-up-An Nd-YAG laser generates a pul6ed laser beam (pulse duration about 30 p8 ) having a wavelength of 1064 nm t~ = 9398 cm~~, which is divided by a beam di~ider into a reference beam and a te~ b~am. ~he reference beEm i~
converted by freguency doubling in a reference ~ample comprising a polyc nstalline powdar of an organic com-pound having a high x (2) into a reference harmonic beam having a wavelength of 532 nm, its int~nsity baing measured by a photodetector. The sE~ple beam irradiate~
the Langmuir-Blodgett monolayer transferred to one ~ide of the glas~ ~lide and being mounted on a rotating s~age perpendi~ular to the optical plane. The ~ample $8 rotated by the incident angle. The frequency-doubled beam i~
measured by a photodetector, itB inten~ity i8 ~tandard-ized by reference ~o the reference ~ignal, :and ~he intensity of the harmonic i~ mea~ured as a function of the incident angle. ~he intensity of the sample is then calibrated by comparl~on with the harmonic of a calib-rated quartz plate. The nonlinearity` (x (~3) ~nd the 203~

average orien~ation of the chromophors (tilting angle with respect ~o the normal of the 8ub8~rat8 ) can be determined from the magni~ude and angle dependence of the intensity of ~he harmonic. The following value~ were found for non linearity:

Concentration of polyacrylic X (2) Tilting acid sngle 0 mg/L250 pm/V 32 (For comparison: The susceptibility of the compound LiNbO3 used commercially in the form of crystal~ i8 about 8 pm/V).

Example 5 (Comparative ~ample) A microscope slide made of glass i8 cleaned as in Example 1 and made hydrophobic. Dye Ia is spread on an aqueous subphase from a ~olution in methylene chloxide (~oncen-tration: 1 mg/ml). The subphases u~ed are aqueou~ ~olu-tions of citric acid, oxalic acid and ~ulfuric ac~d in a concentration of 5 mg/l, which have been brought to a pH
of 7 by adding NaOH. The coating experiments by the Langmuir-Blodgett method were ~arried out a6 des~ribed in Example 1. The test results are listed in the table below:

`" '`' .~, . . .

-2 ~ 3.~

Subphase: Citric acid Oxalic acid Sulfuric acid Subphase temp.: 10, 20C 20~C 20C
S u r f a c e pressure: 3D mN/m 20, 30 mN/m 30 ~/m ~ransfer Transfer of beh.: Iransfer of 3 m~no~rs Transfer of 3 m~nol~ withtrans- 4 ~snDl~
withtrans- fer ra~es withtrans-fer rates below 50 % er rates below 50 % below 50 ~sample 6 Synthesis of dye Ia Q~aternization of 4-picoline using m~thyl iodide 4.85 ml (4.66 g, 50 mmol) of 4-picol$ne are initially introduced at 20C into a glas~ fla~k, and 3.11 ml (7.1 g, 50 mmol) of methyl iodide are carefully metered in with cooling. A~ter the addition i8 comple~e, the 601id formed is taken up in 80 ml of dry acetone s~d refluxed for one hour. The mixture i8 then all~wed to crystallize completely in a freezer, and the product i~
recrystallized again from ethanolg to gi~e 5~99 g (25.5 mmol, 51 %) of a white powder.

lH-NNR (100 MXz, CDC13) : 5 = ~.70 ~, 3~, -CH3); 4.65 (8d 3H, N-CH3); 7.75-7.95 (d, 2H, aromat. H); 9.I-9.3 ~d, 2~, aromat. H) Alkylation of aniline u~th l-bromohexadecane 23.3 g (0.25 mol) of freshly distilled ~niline and 168 g (0.55 mol) of l-bromohexadecane are stirred in a one-neck flask equipped with reflux conden3er under an ~rgon atmosphere at 90C for~3~day~. After cooling, 0.7 1 of toluene i8 added, and the~olution is extracted wlth a 10 % strength aqueous solution of Na2CO3. After extraction ..

, -2 ~ 3 ~ rs~

with a 5 ~ strength agueous HCl ~olution~ the hydrochlor-ide precipitates and ~ 8 filtered o~f through a nutsch filter. ~he free base i8 then liberated by addin~ 10 %
strength Na2CO3, 0.7 1 of toluene i~ added, the organic phase is separated off and drisd with Na2SO4, and the solven~ i8 removed in vacuo. Finally the product i6 recrystalli~ed ~wo more ~ime~ from 1.5 1 of ethanol each time, to give 56.4 g (0.1 mol, 42 %) of a white powder which melts bet~een 47.5 and 49C.

1H-NMR (100 ~Hz, CDC13). ~ = 0.7-1.0 (t, 6H, -CH3); 1.1 1.4 (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 formyla$ion of ~,N-dihexadecylaniline 10 g (18.5 mmol~ of N,N-dihexadecylaniline are made into a paste with 75 ml of dry dimethylformamide, which i8 cooled to 5C, and over a period of 5 minute~ 2.8 g (18.5 mmol) of fre~hly distilled POC13 are added. ~he mixture i~ then allowed to warm to 20~C, ~tirred at this temperature for one hour and heated at 80C for 3 hour6.
After cooling of the reaction solution, the reaction mixture is decomposed with 40 g of ice wat~r and neukr~
$zed with about 10 ml of 5 molar NaOH solution. The precipitate formed i~ filtered off with suction and recrystallized from ethanol to give 4.71 g (8.3 mmol, 45 ~) of a cream-colored powder.

~H-NNR (100 NHz, CDCl3)~ t ~ 0-7-1.0 It, 6~, - CH3); ~
1.4 (m, 56~, -CH2-alkyl); 3.15-3.4 (t, 4H,N-CH2); ~.7-6.9 (d, 2H, aromat. H); 7.65-7.85 (d, 2H, ~romat. H); 9.75 (s, lH, CHO) Reaction of 4-t~ dihexadecyl~aminoben~aldehyde with N-methyl-4-picolinium iodide 0.94 g (4 mmol) of N-methyl-4-picolinium bro~ide~ 2.28 g (4 mmol) of 4~[~,N-dihex~decyl3a~inoben~aldehyde ~nd ~3~ P~

l . 5 ml of piperidine are suspended in 150 ml of ethanol, and the mixture i8 :refluxed for 3 hours. After cooling, the mixture is allowed to complete crystallization in a freezer. The crude produc:t is purified by column chrom-atography on silica gel Si 60 (eluent: CH2C12/CH30H 20:1).
1.5 g (1.9 mmol, 48 P6) of a r~d powder are obtairl0d which melts at temper~tures above 200 C wi~h dec~mposition.

H-NNR ( 100 ~z, CDC13); ~ -- O . 7-l . 0 (t, 6H, --CH3); 1.1-1.4 (m, 56H, -CH2-alkyl); 3.15-3.4 (t, J,H, N-CH2), 4-3 (8~
3H, N-CH3); 7 .1 (m, 6H, aromat . H); 8 . 65 (m, 2H, aromat . H ) :` :

2~3~7~

Table 1 Structural formula Ab60rp~ion in the LB film ~Uc/rlm CH3-(CH2)1s CH3-(cH2)~s ~ CH2-C%2-CH2~0H 475 ~r~

CH3-(CH2)1s CH3-(CH2)1s ~ N+-CH2-CH2-0~ 460 Br~

CH3-(CH2)ls CH3-(CH2)~s ~ N+-CH2-COD-CH3 470 ~r~

CH3-tCH2)l5 CH3-(CH2)15 ~ N+-CH2-~H2-COD~C~3 475 8r~

CH3-(CH2)ls ~N J--~
C~3-(CH2)ls ~ ; 460 CH3-( C}~2 ) 17 ~'~13 ~80 I- .

.

; . .

2J~3~ 7~

Scheme 1 CH3-(CH2)l~

CH3-(CH2)l7 ~ ~ N+--CH
I-Synthetic route:

2 CH3-(CH2)1~-Br + oh~OH 3~CO~ O--(CH2)~.7-CH3 OH O--(CH2)l,-CH3 CH3~N~- CH3 CN3 t Cll~ ) 1, W~ CH3 .. . . . .

- .. : . : . . ~ . , , : . . :

~3~7~

Scheme CH3-(CH2)l7 ~

CH3-(CH2)l7 S~nthatic roùte:
HO

HO o - CH3 CH3-(CH2)l7 O
3 CH3 (CH2)l~-Br e~ CH3-(CH2~l7 ~ O--~H3 ~2CO3 ~H3-( C~2 ) 17 CH3-(CH2)l7 SOCl2 ~H3-(CH2)l7 ~ o H2,c~t.
CH3-(CH2)l7 ~ OH ~ CH3-(CH2)l7 ~ Cl CHg (CH2)l~ ~H3-(CH23l7 CH3-(CH2)~7 o H3C ~ N~-CH3 C~3-(CH2)~7 CH3-(CH2)l7 ~ - I- CN3 (CH2)l7 -O ~ -CH3 CH3-(CH2)17 ~ PiperidiNe CH3-~CH2)~7 0 :

.

.

,, , ,. .; , . .
- . . ' ,~., . ., : . , ;. , :. "

~ ~ 3 ~ r~

~ ~4 Scheme 3 CH3-(CH2)l7 ~ ~N ~ N+- CH3 Synthetic route:

;N+ ~ ~2 ~ cat ~ ~+, NaNO2 o~ N _' ~2~ N

CH3-(CH2)l7 ~0 N--N+~N 2 3 ~ HN ~11 CH3 ( CH2 ) 17 ~N~ ~ ~N~--- : : : :.
.
. ", " ~ .

: ' ' . .

~3~Lr7~

o ~5 _ Scheme 4 CH3-(CH2)ls \N ~
~ CH3 CH3-(CH2)ls ~/
Br~

Synthetic route:

~3-tCH2) CH3 - ( cH2 ) 1 s N, N+~
l' CH3-(CH2)l5 \ ~ j\

CH3 - t CH2 ) l 5 ~ ~N :.

¦ CH3Br CH ( CH2 ) 1 s N~ _~+--CH~
~r~

.. - .- : .. :

: ~ . .. ...

.: . .

2 ~3 3 ~ r~

Scheme 5 CH3-(CH2)17 \~
CH3 - ( cH2 ) 17 ~ CH3 Syrlthetic route:

fi~ /=\ HNO3/H2SO~, ; ~ ~ Zn/HCl DN --~ /N+~

C~I3-(CH2)16-COcl ~
H2N~='\N 4r CH3-(CH~)~6 Y ~ ~\
~/ ~/ ~7--~=)~N

LiAlH4 CH3-(CH2)17 ~ CH3-(~H2)l6-CO
D HN ~N

CX (CX~)16 ~ ~

CH3Br CH3 ' ( C~2 ) 1 7 - ~ DN~ 3 CH~- (CH2~l7 Br . : ~ , . -~ ~ ' ''' ,

Claims (8)

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) Z- ( I) in which R1 H(CH2)nO, H(CH2)nS or , R2 and R3, independently of one another, are H, H(CH2)pO, H(CH2)pS- 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, R4 is -H, -CO-(CH2)tH, -(CH2)t-H
or YR4 is -COO-, -CONH2, H, OH, -SO2(CH2)uH, -CO2(CH2)tH or -CO2 (CH2)vOH, Z is at least in part a polyanion, 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, u is a number from 1-20, and v is a number from 2-10.

2. A layer element as claimed in claim 1, wherein R1 in the amphiphilic compound of the formula I is where n is 14-24, m is 14-24 and R2 and R3 are H
or R1 and R2, independently of one another, are H(CH2)n-O or H(CH2)m-S
where n is 14-24, m- is 14-24 and R3 is H.

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

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,

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, compress-ing the layer remaining after evaporation of the solvent and transferring it to a solid base material using the Langmuir-Blodgett technique.

6. The process as claimed in claim 5, wherein the spreading is carried out on the surface of water containing polyacrylic acid.

7. The process as claimed in claim 5, wherein the spreading is carried out on the surface of water containing polysulfonic acid.

8. The process as claimed in claim 6 or 7, wherein the polyacid concentration is 0.1 mg - 1 g per 1 of water.