Amphiphilic polymers containing silane units and film comprising at least one monomolecular layer produced therefrom

Amphiphilic copolymers containing silanyl groups and composed of derivatives of acrylic and/or methacrylic acid are described, which copolymers are suitable for the production of layer elements by the Langmuir-Blodgett method. Layer elements of this type can be used for optical waveguide systems and for the production of optical filters and for lithographic purposes.

BACKGROUND OF THE INVENTION 
The invention relates to specific amphiphilic copolymers containing silane 
units, a film comprising at least one monomolecular layer of these 
molecules on a solid support (=so-called layer elements), and a process 
for the preparation of the layer elements and their use. 
Ordered layers of organic polymers having long-chain side groups are 
predominantly prepared by using the Langmuir-Blodgett (LB) method. In this 
method, molecules are spread on a water surface and the long alkyl side 
groups are aligned in parallel by decreasing the area per molecule. At a 
constant pressure, the molecules are applied to a substrate by immersion 
and withdrawal. Per dipping operation, one monomolecular layer is 
transferred with retention of its order. 
LB films are constructed by using amphiphilic molecules, i.e. molecules 
having a hydrophilic end (a "head") and a hydrophobic end (a "tail"). In 
order to achieve higher stability of the LB films, polymeric LB films have 
also already been prepared. 
Preparation of polymeric LB films can be carried out by polymerization of 
unsaturated amphiphiles after formation of the monomer film. However, 
organic polymers having long alkyl side chains have also already been used 
directly for preparation of the layer (WO 83/03165, R. Elbert, A. 
Laschewsky and H. Ringsdorf, J. Am. Chem. Soc. 107, 4134-4141 (1985)). 
Copolymer films have also already been described (A. Laschewsky, H. 
Ringsdorf, G. Schmidt and J. Schneider, J. Am. Chem. Soc. 109, 788-796 
(1987)). In these copolymers, one of the comonomers carries at least one 
long alkyl chain, while the second monomer is water-soluble, or carries at 
least polar and hydrophilic groups. If such polymer films are intended to 
be used as resist materials, such as, for example, described by R. Jones, 
C. S. Winter, R. H. Tredgold, P. Hodge and A. Hoorfar, Polymer 28, 
1619-1626 (1987), the problem of insufficient etching stability of these 
films during plasma etching arises. 
However, it is known from resist technology that the etching stability of 
photoresists in an oxygen plasma can be drastically increased by 
incorporating silicon compounds. Thus, aliphatic and/or aromatic 
hydroxyl-carrying polymeric binders have been described which contain 
silanyl groups in the side chain which, as components of a photosensitive 
mixture, give this mixture increased resistance to plasma etching 
(EP-A-0,337,188). The photosensitive layer, which is formed by 
spin-coating the substrate with a resist solution containing such a binder 
and compounds from the class of compounds of o-quinone diazides, has a 
layer thickness of 0.3 to 10 .mu.m. A disadvantage for microelectronic 
applications, for example high-resolution electron beam lithography, is 
the relatively high layer thickness of resist films of this type. 
Furthermore, Langmuir-Blodgett layers of amphiphilic polysiloxanes are 
known (Adv. Mater. 3 (1991), 27). It is true that they have good etching 
resistance in an oxygen plasma, but for many applications they have only 
insufficient temperature resistance, owing to the siloxane main chain. 
Accordingly, the object is to prepare polymers from which Langmuir-Blodgett 
films can be formed which have improved resistance to temperature and 
plasma etching. 
SUMMARY OF THE INVENTION 
The invention relates to amphiphilic copolymers containing silanyl groups 
and structural units derived from at least one monomer of the formula I 
##STR1## 
and at least one monomer of the formula II 
##STR2## 
in which A-- is CH.sub.3 -- or CF.sub.3 --, 
--B-- is --CH.sub.2 -- or --CF.sub.2 --, 
n is an integer from 5 to 25, 
m is an integer from zero to 12, 
--X-- is --O--, --NR.sup.1 -- or --Z--, in which 
R.sup.1 -- is H--, CH.sub.3 --(CH.sub.2).sub.n -- or CF.sub.3 
--(CF.sub.2).sub.n --(CH.sub.2).sub.m -- 
--Z-- is --X'--(CH.sub.2).sub.p --X' or 
##STR3## 
p is an integer from 2 to 10, l is an integer from 1 to 10 and --X'-- is 
--O-- or --NR.sup.1 --, 
--Y is --H, --CH.sub.3, --CN, --Cl, --Br or --F, 
--D is --SiR.sup.2 (SiR.sup.2.sub.3).sub.2, --Si(SiR.sup.2.sub.3).sub.3, 
--SiR.sup.2.sub.2 --SiR.sup.2.sub.3 or --(SiR.sup.2.sub.2).sub.2 
--SiR.sup.2.sub.3, 
in which R.sup.2 is C.sub.1 -C.sub.3 -alkyl, 
--E-- is C.sub.1 -C.sub.4 -alkylene and 
--L-- is

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Preferred structural units derived from monomers of the formula I carry 
only one long side chain, i.e. the function group --X--, which is --O--, 
--NH-- or --Z-- and --X'--, which is --O-- or --NH--. 
Preferred structural units derived from monomers of the formula II are 
those in which 
--D is --(SiR.sup.2.sub.2)--SiR.sup.2.sub.3 and R.sup.2 is C.sub.1 -C.sub.3 
-alkyl, in particular methyl, 
--E-- is C.sub.2 -alkylene, 
--L-- is --NH-- or 
##STR5## 
and --Y is --H or --CH.sub.3. 
The synthesis of the monomers of the formula I can be carried out by known 
methods by reaction of a vinylcarboxylic acid or an activated derivative 
of this carboxylic acid, for example an acid halide, with a longchain 
alcohol or amine of the formula IV 
EQU A--B.sub.n --(CH.sub.2).sub.m --X'--H (IV) 
in which A--, --B--, --X'--, m and n have the abovementioned meaning. 
Monomers of the formula I containing structural units Z can be prepared 
first by reaction of a dicarboxylic acid of the formula (V) 
EQU HOOC--(CH.sub.2).sub.1 --COOH (V) 
or of an activated derivative of this dicarboxylic acid, such as, for 
example, of an acid anhydride, an ester or an acid halide, with an 
unsaturated alcohol or amine of the formula (VI) 
##STR6## 
in which l, p, Y and X' have the abovementioned meaning, to give the 
monoester, followed by condensation with a long-chain alcohol or amine of 
the formula VII 
EQU A--B.sub.n --(CH.sub.2).sub.m --X'--H (VII) 
in which A, B, X', n and m have the abovementioned meaning. 
However, they can also be prepared by the reverse reaction sequence, i.e. 
by reaction of the dicarboxylic acid of the formula (V) or of one of its 
reactive derivatives with a long-chain alcohol or amine of the formula 
(VII), followed by esterification of the intermediate with the unsaturated 
alcohol of the formula (VI). 
The monomers containing silanyl groups of the formula II can be prepared by 
reaction of a vinylcarboxylic acid or of an activated derivative thereof 
with a silylating reagent of the formula VIII 
EQU D--E--L'--H (VIII) 
in which --L'-- is --NR.sup.1 or --O--, and R.sup.1, D and L have the 
abovementioned meaning. 
Silylating reagents of the formula VIII are described in EP-A-0,336,276. 
The monomers of the formula II can furthermore be synthesized by reaction 
of isocyanato-containing silylating reagents of the formula IX 
EQU D--E--N.dbd.C.dbd.O (IX) 
in which D and E have the abovementioned meaning, with an unsaturated 
alcohol or amine of the formula VI or of the formula X 
##STR7## 
Copolymers (i.e. ter- and multipolymers) which in addition to the 
structural units derived from monomers of formula I and II contain at 
least one structural unit derived from further functional comonomers, for 
example those leading to radiation-induced crosslinking of the polymers, 
are also suitable for the purposes of the invention. Further comonomers 
are also monomers having long alkyl chains, for example monomers such as 
described by Jones et al., Elbert et al. and Laschewsky et al. in the 
abovementioned publications and in WO 83/03165. Moreover, hydrophilic, 
preferably water-soluble, vinyl monomers, such as, for example, itaconic 
acid, fumaric acid, maleic acid, acrylic acid, cyanoacrylic acid and 
methacrylic acid or derivatives thereof are suitable as comonomers. 
Particular preference is given to those comonomers carrying 
radiation-crosslinkable units. 
The proportion of structural units derived from silanylcontaining monomers 
of the formula II in the copolymer can be 5 to 98, preferably 30 to 85 and 
in particular 30 to 70, mol %. The proportion of structural units derived 
from monomers of the formula I in the copolymer can be 95 to 2, preferably 
70 to 15 and in particular 70 to 30, mol %, the proportions of the 
structural units adding up to a total of 100 mol %. 
In copolymers containing structural units derived from at least one monomer 
each of the formula I and II and at least one further functional 
comonomer, preferably containing a radiation-crosslinkable unit, the 
proportion of structural units derived from monomers of the formula I can 
be 90 to 5, preferably 60 to 20, mol %, the proportion of structural units 
derived from monomers of the formula II can be 5 to 90, preferably 20 to 
60, mol %, and the proportion of structural units derived from further 
functional comonomers can be 5 to 60, preferably 20 to 40, mol %, the 
proportions of the structural units adding up to a total of 100 mol %. 
The polymerization is preferably carried out as a free-radical 
polymerization with the addition of a free-radical initiator using 
conventional methods. 
The polymers or films according to the invention can also be mixed with 
further appropriate components, for example with dyes, amphiphilic 
crosslinking agents, monomeric or polymeric amphiphiles. The proportion of 
these additives in such mixtures can be 1 to 80% by weight. 
The films are prepared according to the invention by dissolving the organic 
polymers or mixtures containing preferably 10-100% by weight of the 
polymers according to the invention in a substantially volatile, 
water-immiscible solvent and placing (=spreading) them on the surface of 
an aqueous solution in a film balance. The average area per repeating unit 
is calculated from the dimension of the surface, the spreading volume and 
the concentration of the solution. Phase transitions during compression of 
the molecules can be monitored via the force/area isotherm. 
The molecules are compressed by means of a barrier, as a result of which 
the alkyl chains are aligned substantially perpendicular to the boundary 
layer with increasing surface density. During compression, a highly 
ordered monomolecular film, whose constant layer thickness is 
substantially determined by the chain length of the alkyl side chain of 
the polymers and their tilting angle (i.e. the angle at which the 
molecular chains on the water surface are tilted with respect to the 
normal) is formed at the boundary layer through self-organization of the 
molecules. The typical thickness of such a film is 0.5-3 nm. 
At a constant pressure, the film is removed from the water surface by 
immersion or withdrawal of a suitable substrate with retention of the 
order. 
In most cases, the subphase used for the monofilm preparation is water or 
aqueous solutions. However, other liquids having a high surface tension, 
such as, for example, glycerol, glycol, dimethyl sulfoxide, 
dimethylformamide or acetonitrile can also be used. 
Suitable substrates are any solid, preferably dimensionally stable, 
substrates made of a variety of materials. The substrates which serve as 
support can be, for example, transparent or opaque, electrically 
conducting or insulating. The substrate can be hydrophobic or hydrophilic. 
The surface of the substrate to which the LB layer is applied can have 
been made hydrophobic. The surface of the substrate to be coated should be 
as pure as possible so as not to disturb formation of a thin ordered 
layer. The presence of surface-active substances on the surface of the 
substrates to be coated can in particular impair preparation of the layer. 
It is possible to provide the substrates serving as support with an 
intermediate layer on the surface to be coated before applying the LB 
films, in order to improve, for example, adhesion of the film to the 
substrate. 
Examples of materials which can be used for the substrates are metals, such 
as, for example, gold, platinum, nickel, palladium, aluminum, chromium, 
niobium, tantalum, titanium, steel and the like. Further suitable 
materials for the substrates are plastics, such as, for example, 
polyesters, for example polyethylene terephthalate or polybutylene 
terephthalate, polyvinyl chloride, polyvinylidene chloride, 
polytetrafluoroethylene, polystyrene, polyethylene or polypropylene. 
In particular semiconductors, such as silicon, germanium or gallium 
arsenide or else glass, silicon dioxide, ceramic materials or cellulose 
products are suitable for the substrates. If required, the surface of 
glass and other hydrophilic substrates can be made hydrophobic in a manner 
known per se by reaction with alkylsilanes or hexamethyldisilazanes. The 
selection of the substrate materials depends primarily on the intended 
application of the layer elements according to the invention. As a rule, 
for optical elements, transparent substrates are used as supports. If the 
layer elements according to the invention are used, for example, in 
electronics or in electrochemical processes, the substrates used are in 
particular electrically conducting materials, such as metal or metallic 
surface layers, for example on plastic sheets or glass. 
The substrates which serve as carriers for the films according to the 
invention can, depending on the particular application, have any desired 
form. For example, they can be in the form of films, sheets, slabs, tapes 
or even cylinders or can be selected from other forms. In general, the 
supports will be flat planar substrates, such as, for example, films, 
sheets, slabs, tapes and the like. The surface of the substrates to be 
coated is preferably smooth, as is customary for the preparation of LB 
films. In the case of flat planar substrates, the films according to the 
invention can be applied to one or both surfaces of the substrate. 
The multi-layer structure which can be readily prepared from the polymers 
according to the invention is distinguished by a small number of defects 
and good temperature and etching resistance. 
Such films on substrates are suitable, for example, for optical waveguide 
or for the production of filters for optical purposes. Substrates 
containing films prepared from copolymers according to the invention, 
which contain radiationcrosslinkable units, are also used for lithographic 
purposes. Owing to the low critical surface tension, the films are also 
suitable for improving the friction properties of materials and for the 
production of protective layers. 
The invention is illustrated in more detail by the examples which follow. 
The solvents used for the synthesis of the monomers are dried by 
conventional methods (for example by molecular sieve). The polymerizations 
are carried out in an inert gas atmosphere, for example of nitrogen. 
Example 1 
Synthesis of the disilane monomer 1 
##STR8## 
5.8 of 2-pentamethyldisilylethylamine hydrochloride are dissolved in about 
100 ml of dichloromethane and extracted twice by shaking with 100 ml each 
of 2M NaOH. The organic phase is dried with Na.sub.2 SO.sub.4, and the 
solvent is removed in vacuo. 50 mg of 2,6-di-tert.-butyl-p-cresol are 
added to the remaining clear liquid, and the mixture is dissolved in 40 ml 
of anhydrous tetrahydrofuran (dichloromethane, dioxane and toluene are 
also suitable solvents), the solution is cooled to 2.degree. C., 4.5 ml of 
anhydrous triethylamine are added, and 2.7 ml of acryloyl chloride, 
dissolved in 30 ml of anhydrous tetrahydrofuran, are metered in at 
2.degree. C. over a period of 30 minutes. The ice bath is then removed, 
and the reaction mixture, after reaching a temperature of 
20.degree.-25.degree. C., is stirred for another 2 hours. The reaction 
mixture, after addition of 100 ml of dichloromethane, is then extracted 
twice with 50 ml each of 1M HCl, the organic phase is dried with Na.sub.2 
SO.sub.4 and the solvent is removed in vacuo. The remaining solid is 
purified by recrystallization from n-hexane, giving 4.95 g (80% of theory) 
of a white powder. 
.sup.1 H NMR (100 MHz, CDCl.sub.3): 
.delta.=-0.1-0.1 (m, 15H, Si--CH.sub.3), 0.7-1.0 (m, 2H, SiCH.sub.2), 
3.1-3.5 (m, 2H, N--CH.sub.2), 5.2-5.8 (m, 2H, --NH-- and .dbd.CH--CO), 
5.8-6.4 (m, 2H, .dbd.CH.sub.2). 
Example 2 
Synthesis of the disilane monomer 2 
##STR9## 
6.04 g of the disilane isocyanate are dissolved together with 35 mg of 
1,4-diazabicyclo[2.2.2]octane in 50 ml of dichloromethane. The solution is 
cooled in an ice/sodium chloride bath to 0.degree. C, and a mixture of 
4.25 ml of 2-hydroxyethyl methacrylate, 5 mg of 
2,6-di-tert.-butyl-p-cresol and 25 ml of dichloromethane is metered in 
over a period of 15 minutes. After addition is complete, the reaction 
mixture is heated to the boiling temperature over a period of 30 minutes, 
and boiled at the boiling temperature for 20 hours. After cooling to a 
temperature of 20.degree.-25.degree. C., the reaction mixture is extracted 
twice by shaking with 100 ml each of 1M HCl and water, the organic phase 
is dried with Na.sub.2 SO.sub.4, and the solvent is removed in vacuo. 50 
mg of 2,6-di-tert.-butyl-p-cresol are added to the remaining oily 
substance, and the mixture is purified by column chromatography (eluent: 
n-hexane/ethyl acetate 3:1 (volumeratio)). This gives 15 g (65% of theory) 
of a colorless oil. 
.sup.1 H NMR (100 MHz, CDCl.sub.3): .delta.=-0.1-0.1 (m, 15H, 
Si--CH.sub.3), 0.7-1.0 (m, 2H, SiCH.sub.2), 1.7-1.9 (m, 3H, C--CH.sub.3), 
3.1-3.5 (m, 2H, N--CH.sub.2), 4.2-4.3 (s, 4H, O--CH.sub.2 --CH.sub.2 
--O--CO), 4.4-4.7 (m, 1H, NH), 5.4-6.2 (m, 2H, .dbd.CH.sub.2). 
Example 3 
Free-radical copolymerization of the disilane monomer 1 with 
N-octadecylacrylamide 
2.0 g of N-octadecylacrylamide and 0.622 g of the disilane monomer 1 are 
dissolved in 20 ml of tetrahydrofuran, and 10.2 mg of 
azobisisobutyronitrile are added. The solution is placed in a three-necked 
flask equipped with reflux condenser (with gas-discharge tube and bubble 
counter), thermometer and gas introduction tube, and the mixture is 
flushed with nitrogen at a temperature of 20.degree.-25.degree. C. for one 
hour. The reaction mixture is then heated to the boiling temperature and 
refluxed at the boiling temperature for 7 hours with continuous stirring 
(magnetic stirrer). The polymer is precipitated by pouring the reaction 
solution cooled to a temperature of 20.degree.-25.degree. C. into 
methanol, and the product is filtered off with suction. In order to free 
it from residual monomer, it is dissolved two more times in 
tetrahydrofuran and precipitated by pouring into methanol, giving 1.9 g of 
a white fine-particle material which is insoluble in methanol and soluble 
in tetrahydrofuran. Determination of the molecular weight by means of gel 
permeation chromatography gives an M.sub.w of 4,800 and an M.sub.n of 
2,600 dalton (polystyrene calibration). Elemental analysis (71.4% by 
weight of C, 11.7% by weight of H, 4.6% by weight of N, 5.5% by weight of 
O) gives a copolymer composition of 1 part of long-chain substituted 
monomer and 0.45.+-.0.1 part of disilane monomer. 
Example 4 
Free-radical copolymerization of the disilane monomer 1 with 
N-octadecylacrylamide 
2.0 g of N-octadecylacrylamide and 1.244 g of the disilane monomer 1 are 
dissolved in 20 ml of tetrahydrofuran, and 10.2 mg of 
azobisisobutyronitrile are added. The solution is placed in a three-necked 
flask equipped with reflux condenser (with gas-discharge tube and bubble 
counter), thermometer and gas introduction tube, and the mixture is 
flushed with nitrogen at room temperature for one hour. The reaction 
mixture is then heated to the boiling temperature and refluxed at the 
boiling temperature for 7 hours with continuous stirring. The polymer is 
precipitated by pouring the reaction solution cooled to a temperature of 
20.degree.-25.degree. C. into methanol, and the product is filtered off 
with suction. In order to free it from residual monomer, it is dissolved 
two more times in tetrahydrofuran and precipitated by pouring into 
methanol, giving 1.1 g of a white fine-particle material which is 
insoluble in methanol and soluble in tetrahydrofuran. Determination of the 
molecular weight by means of gel permeation chromatography gives an 
M.sub.w of 4,600 and an M.sub.n of 2,500 dalton (polystyrene calibration). 
Elemental analysis (68.4% by weight of C, 11.1% by weight of H, 4.9% by 
weight of N, 5.4% by weight of O) gives a copolymer composition of 1 part 
of long-chain substituted monomer and 0.9.+-.0.2 part of disilane monomer. 
Example 5 
Free-radical copolymerization of the disilane monomer 1 with 
N-octadecylacrylamide 
2.0 g of N-octadecylacrylamide and 2.49 g of the disilane monomer 1 are 
dissolved in 20 ml of tetrahydrofuran, and 10.2 mg of 
azobisisobutyronitrile are added. The solution is placed in a three-necked 
flask equipped with reflux condenser (with gas-discharge tube and bubble 
counter), thermometer and gas introduction tube, and the mixture is 
flushed with nitrogen at a temperature of 20.degree.-25.degree. C. for one 
hour. The reaction mixture is then heated to the boiling temperature and 
refluxed at the boiling temperature for 7 hours with continuous stirring. 
The polymer is precipitated by pouring the reaction solution cooled to 
20.degree.-25.degree. C. into methanol, and the product is filtered off 
with suction. In order to free it from residual monomer, it is dissolved 
two more times in tetrahydrofuran and precipitated by pouring into 
methanol, giving 2.4 g of a white fine-particle material which is 
insoluble in methanol and soluble in tetrahydrofuran. Determination of the 
molecular weight by means of gel permeation chromatography gives an 
M.sub.w of 5,700 and an M.sub.n of 4,300 dalton (polystyrene calibration). 
Elemental analysis (61.9% by weight of C, 11.1% by weight of H, 5.4% by 
weight of N) gives a copolymer composition of 1 part of long-chain 
substituted monomer and 2.4.+-.0.1 part of disilane monomer. 
Example 6 
Free-radical copolymerization of the disilane monomer 1 with 
N-octadecylacrylamide 
1.0 g of N-octadecylacrylamide and 3.11 g of the disilane monomer 1 are 
dissolved in 20 ml of tetrahydrofuran, and 5.1 mg of 
azobisisobutyronitrile are added. The solution is placed in a three-necked 
flask equipped with reflux condenser (with gas-discharge tube and bubble 
counter), thermometer and gas introduction tube, and the mixture is 
flushed with nitrogen at a temperature of 20.degree.-25.degree. C. for one 
hour. The reaction mixture is then heated to the boiling temperature and 
refluxed at the boiling temperature for 7 hours with continuous stirring. 
The polymer is precipitated by pouring the reaction solution cooled to a 
temperature of 20.degree.-25.degree. C. into methanol, and the product is 
filtered off with suction. In order to free it from residual monomer, it 
is dissolved two more times in tetrahydrofuran and precipitated by pouring 
into methanol, giving 4.2 g of a white fine-particle material which is 
insoluble in methanol and soluble in tetrahydrofuran. Determination of the 
molecular weight by means of gel permeation chromatography gives an 
M.sub.w of 10,000 and an M.sub.n of 6,200 dalton (polystyrene 
calibration). Elemental analysis (57.8% by weight of C, 10.6% by weight of 
H, 5.6% by weight of N) gives a copolymer composition of 1 part of 
long-chain substituted monomer and 5.1.+-.0.6 part of disilane monomer. 
Example 7 
Free-radical copolymerization of the disilane monomer 2 with 
N-octadecylacrylamide 
0.93 g of N-octadecylacrylamide and 0.50 g of the disilane monomer 2 are 
dissolved in 30 ml of tetrahydrofuran, and 4.4 mg of 
azobisisobutyronitrile are added. The solution is placed in a three-necked 
flask equipped with reflux condenser (with gas-discharge tube and bubble 
counter), thermometer and gas introduction tube, and the mixture is 
flushed with nitrogen at a temperature of 20.degree.-25.degree. C. for one 
hour. The reaction mixture is then heated to the boiling temperature and 
refluxed at the boiling temperature for 6 hours with continuous stirring. 
The polymer is precipitated by pouring the reaction solution into 
methanol, and the product is filtered off with suction. In order to free 
it from residual monomer, it is dissolved two more times in 
tetrahydrofuran and precipitated by pouring into methanol, giving 0.58 g 
of a white fine-particle material which is insoluble in methanol and 
soluble in tetrahydrofuran. Determination of the molecular weight by means 
of gel permeation chromatography gives an M.sub.w of 5,400 and an M.sub.n 
of 2,500 dalton (polystyrene calibration). Elemental analysis (65.2% by 
weight of C, 10.3% by weight of H, 4.2% by weight of N) gives a copolymer 
composition of 1 part of long-chain substituted monomer and 1.3.+-.0.3 
part of disilane monomer. 
Example 8 
Free-radical copolymerization of the disilane monomer 2 with 
N-octadecylacrylamide 
0.93 g of N-octadecylacrylamide and 0.99 g of the disilane monomer 2 are 
dissolved in 30 ml of tetrahydrofuran, and 4.4 mg of 
azobisisobutyronitrile are added. The solution is placed in a three-necked 
flask equipped with reflux condenser (with gas-discharge tube and bubble 
counter), thermometer and gas introduction tube, and the mixture is 
flushed with nitrogen at a temperature of 20.degree.-25.degree. C. for one 
hour. The reaction mixture is then heated to the boiling temperature and 
refluxed at the boiling temperature for 7.5 hours with continuous 
stirring. The polymer is precipitated by pouring the reaction solution 
cooled to a temperature of 20.degree.-25.degree. C. into methanol, and the 
product is filtered off with suction. In order to free it from residual 
monomer, it is dissolved two more times in hot tetrahydrofuran and 
precipitated by pouring into methanol, giving 0.46 g of a white 
fine-particle material which is insoluble in methanol and soluble in hot 
tetrahydrofuran. Determination of the molecular weight by means of gel 
permeation chromatography could not be carried out, due to the low 
solubility at 20.degree. C. Elemental analysis (62.1% by weight of C, 
10.5% by weight of H, 4.1% by weight of N) gives a copolymer composition 
of 1 part of long-chain substituted monomer and 1.3.+-.0.1 part of 
disilane monomer. 
Example 9 
Free-radical copolymerization of the disilane monomer 2 with 
N-octadecylacrylamide 
0.93 g of N-octadecylacrylamide and 1.99 g of the disilane monomer 2 are 
dissolved in 30 ml of tetrahydrofuran, and 4.4 mg of 
azobisisobutyronitrile are added. The solution is placed in a three-necked 
flask equipped with reflux condenser (with gas-discharge tube and bubble 
counter), thermometer and gas introduction tube, and the mixture is 
flushed with nitrogen at a temperature of 20.degree.-25.degree. C. for one 
hour. The reaction mixture is then heated to the boiling temperature and 
refluxed at the boiling temperature for 7.5 hours with continuous 
stirring. The polymer is precipitated by pouring the reaction solution 
cooled to a temperature of 20.degree.-25.degree. C. into methanol, and the 
product is filtered off with suction. In order to free it from residual 
monomer, it is dissolved two more times in hot tetrahydrofuran and 
precipitated by pouring into methanol, giving 1.0 g of a white 
fine-particle material which is insoluble in methanol and soluble in hot 
tetrahydrofuran. Determination of the molecular weight by means of gel 
permeation chromatography could not be carried out, due to the low 
solubility at 20.degree. C. Elemental analysis (59.0% by weight of C, 
10.0% by weight of H, 4.39% by weight of N) gives a copolymer composition 
of 1 part of long-chain substituted monomer and 1.9.+-.0.4 part of 
disilane monomer. 
Example 10 
Film preparation by the Langmuir-Blodgett method 
A microscope slide made of glass (76 mm.times.26 mm) is cleaned by the 
following method: 
The glass is placed in a freshly prepared mixture of four parts of conc. 
H.sub.2 SO.sub.4 and one part of 30% H.sub.2 O.sub.2, whose temperature is 
60.degree. C., for one hour, rinsed off with water of high purity and 
cleaned in an alkaline, surfactant-free cleaning solution, for example 
.RTM.Extran AP 11 (conc. 2-4 g/l) for 15 minutes at a temperature of 
50.degree. C. by means of ultrasound. The glass is then thoroughly rinsed 
with water of high purity (18 mohm, free of particles) and dried in a warm 
air stream. The glass is then made hydrophobic by treating it with 
hexamethyldisilazane vapor (for 10 minutes at a temperature of 70.degree. 
C.). 
Multilayers comprising the polymer prepared in Example 3 are transferred by 
the Langmuir and Blodgett method to the glass support by spreading 0.2 
cm.sup.3 of a solution of 9.3 mg of the polymer in 10 cm.sup.3 of a 9:1 
(volume ratio) mixture of methylene chloride and tetrahydrofuran on an 
aqueous subphase at a subphase temperature of 10.degree. C. in a Langmuir 
film balance. By reducing the monofilm-covered water surface, the pressure 
is adjusted to 20 mN/m and kept constant at this value. The support is now 
immersed perpendicularly from above through the water surface into the 
film balance (immersion rate: 20 mm/min.) and after a short pause (10 
sec.) at the lower turnaround point again withdrawn (withdrawal rate: 20 
mm/min.). Each immersion and also each withdrawal process transfers one 
monolayer to the support. By repeating the dipping process several times 
after a wait of one minute each at the upper turnaround point, a total of 
10 double layers are transferred. The transfer ratios are around 90%. Even 
when 50 and more monolayers are transferred, optically clear, transparent 
films are obtained. 
Films are also obtained from the polymers prepared in Examples 4, 5 and 6, 
using the same procedure. The transfer conditions for these polymers are 
as follows: 
______________________________________ 
Polymer from Example: 
4 5 6 
______________________________________ 
Subphase temperature: 
10.degree. C. 
10.degree. C. 
10.degree. C. 
Pressure: 20 mN/m 20 mN/m 20 mN/m 
Transfer ratio: 
90% 70% 80% 
______________________________________ 
Example 11 
Ellipsometric measurements of the layer thickness and the refractive index 
Silicon chips (40 mm.times.10 mm) are cut from a silicon wafer and cleaned 
as follows: 
1. Treatment for 1 hour in a freshly prepared mixture comprising one part 
of 30% H.sub.2 O.sub.2 and four parts of conc. H.sub.2 SO.sub.4 whose 
temperature is 60.degree. C. They are then rinsed with water of high 
purity. 
2. Immersion in an NH.sub.4 F-buffered HF solution for 30 seconds, followed 
again by rinsing using water of high purity. After this treatment, the 
silicon chips are hydrophobic (contact angle with water: 75.degree. C.). 
Layers made from the polymers prepared in Examples 3, 4, 5 and 6 are 
transferred to the silicon chip by the Langmuir and Blodgett method under 
the same conditions as in Example 10. Specimens containing 10, 30, 50 and 
70 monolayers, respectively, of the individual polymers are prepared, and 
the layer thicknesses and the refractive index of the LB films are 
measured ellipsometrically. 
______________________________________ 
Results of the 
measurements: 
Polymer from Example: 
3 4 5 6 
______________________________________ 
Refractive index at 
1.499 1.486 1.454 
1.477 
633 nm: 
Layer thickness in 
1.990 1.460 0.698 
0.830 
nm/monolayer: 
______________________________________ 
Example 12 
Measurements of heat stability 
Silicon chips (40 mm.times.10 mm) are cut from a thermally oxidized silicon 
wafer (thickness of the oxide layer: 160 nm) and placed in a freshly 
prepared mixture comprising one part of 30% H.sub.2 O.sub.2 and four parts 
of conc. H.sub.2 SO.sub.4 at a temperature of 60.degree. C. for one hour. 
After thorough rinsing using water of high purity, the chip is treated in 
an ultrasound bath with an alkaline, surfactant-free cleaning solution, 
for example .RTM.Extran AP 11 (conc. 2-4 g/l) at a temperature of 
50.degree. C. for 15 minutes, thoroughly rinsed with water of high purity 
and dried in a warm air stream. It is then made hydrophobic by means of a 
treatment with hexamethyldisilazane vapour (10 minutes at a temperature of 
70.degree. C.). 
Coating by the LB method with 8 monolayers each is carried out as described 
in Example 10, using the polymers prepared in Examples 3, 4, 5 and 6. 
The coated carrier is heated in a special apparatus at a linear temperature 
gradient (0.5.degree. C./sec.). During the heating-up process, the 
thickness of the LB film is measured by the intensity of a perpendicularly 
polarized laser beam (633 nm) reflected by the specimen. The temperature 
at which the first change in layer thickness takes place is 140.degree. C. 
in layers made from the polymer prepared in Example 3, 130.degree. C. in 
layers made from the polymer prepared in Example 4, 120.degree. C. in 
layers made from the polymer prepared in Example 5, and 130.degree. C. in 
layers made from the polymer prepared in Example 6. (For comparison: in LB 
layers made from 22-tricosenic acid, this temperature is 70.degree. C.) 
Example 13 
Measurements of the critical surface tension 
Silicon chips (40 mm.times.10 mm) are cleaned as in Example 11 and coated 
as in Example 11 with eight monolayers each made from the polymers 
prepared in Examples 3, 4, 5 and 6. Droplets of a liquid from the series 
of n-alkanes (C.sub.9 H.sub.20 -C.sub.16 H.sub.34) are placed on the 
surface of the transferred layers, and the contact angles of the droplets 
with the surface are measured. The critical surface tension is determined 
from these contact angles by the method of Zisman (W. A. Zisman, Adv. 
Chem. Ser., 43 (1964), 1-51 and Phys. Chem. Surfaces, A. W. Adamson, New 
York 1982). The following values are found: 
______________________________________ 
Polymer from Example 
Crit. surface tension [mN/m] 
______________________________________ 
3 21.7 
4 23.8 
5 25.2 
6 25.2 
______________________________________ 
(For comparison: A polyethylene surface gives a value of 31 mN/m in this 
measurement).