04/887454

11/30/1971

12/22/1969

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The Procter & Gamble Company (Cincinnati, OH)

556/425

516/DIG.007, 516/199, 556/463, 556/454, 516/DIG.001, 424/54, 556/456

A61K8/58; A61K8/896; A61Q11/00; A61Q17/00; A61Q19/10; C07F7/08; C08G77/04; C11D3/37; A61K8/30; A61K8/72; C07F7/00; C08G77/00; C07F7/10

260/448.2N,448.2E,448.2P

Levow, Tobias E.

Shaver P. F.

What is claimed is

1. Quaternary ammonium salts of cyclic siloxane polymers represented by the formula

2. The polymers of claim 1 wherein

3. The polymers of claim 2 wherein

4. The compound ##SPC14##

5. The compound of claim 4 wherein

6. The compound of claim 5 wherein

7. The process of preparing quaternary ammonium salts of cyclic siloxane polymers comprising

8. The process of claim 7 wherein

9. The process of claim 8 wherein

BACKGROUND OF THE INVENTION

1. Field of the Invention

Cationic surfactants, as a broad class, contain a long-chain hydrophobic group attached to a positively charged hydrophilic group. Typically such a surfactant contains a long-chain hydrocarbon chain attached to a positively charged quaternary ammonium group. Such a compound is well known to be surface active in aqueous media because the hydrophilic quaternary ammonium portion of each molecule is strongly pulled into the solution whereas the hydrophobic hydrocarbon chain is only weakly attracted; as a result an oriented monolayer tends to form at the air/water surface (thereby reducing surface tension) and at the interfaces of any relatively hydrophobic materials (e.g. polyethylene, mineral oil, etc.) that are in the water solution. In fact this is also the means whereby micelles form at relatively low concentrations of surface-active substances and whereby mesomorphic phases form at relatively high concentrations.

As a few molecules of a given surfactant are added to water they form a true solution. As more are added they abruptly form micelles at a specific concentration, which is unique for each compound, and which is referred to in the art as the "critical micelle concentration" or "c.m.c." As additional surfactant is added the micelles increase in number until at another, higher, specific concentration (which is a function of temperature) a mesomorphic phase is formed which contains major amounts of both surfactant and water aligned in a specific structure which is determinable for each surfactant individually by X-ray diffraction analysis.

The c.m.c. varies enormously with the specific structure of the surfactant molecule, and depends upon the relative size and strength of the hydrophobic and hydrophilic portions of the molecule. The c.m.c. may be as low as a few parts per million or it may be as high as about 1 percent. The threshold of the mesomorphic phase also varies; typically it is in the range of 20-40 percent, though it may be either higher or lower in specific cases.

A compound with a relatively low c.m.c. is said in the art to have high "surface activity." That is to say that a low concentration is required to saturate the solution with the molecularly dissolved species and to initiate the formation of micelles within the solution and the formation of oriented monolayers at the various interfaces that are present.

The siloxane structure is well known to be an unusually effective hydrophobe. Just as silicone oils are, in general, less compatible with water than mineral oils, so silicone-containing surfactants have, in general, lower c.m.c.'s and provide lower surface tensions than surfactants whose hydrophobic portion is entirely hydrocarbon in nature. They also form mesomorphic phases in water solution. As will be discussed fully infra, the compounds of the instant invention belong to this class of surfactants and exhibit an exceptionally high degree of surface activity.

2. Prior Art

A series of silicone-containing surfactants are commercially available having the structure

(CH ₃ ) ₃ --Si--O--[--Si--(CH ₃ ) ₂ --O--] _n --(CH ₂ ) _m --X

where X is a cationic, anionic, or nonionic hydrophilic group. These surfactants contain a single hydrophilic group on each long-chain linear siloxane molecule.

A silane structure is disclosed in Netherlands Application 65/17163 (July 1, 1966) to Union Carbide Corporation:

wherein Ar is an arylene radical, R is an alkylene radical, R' is a monovalent hydrocarbon radical, X is a radical selected from the group consisting of halogen and OR' wherein R' is as defined above, R" ₃ N taken collectively represents a tertiary amine selected from the group consisting of heterocyclic tertiary amines wherein the amino nitrogen is present in a ring structure with carbon atoms and tertiary amines wherein the amino nitrogen represented by N is bonded to three monovalent organic radicals represented by R", n is an integer having a value of from 0 to 1, a is an integer having a value of from 1 to 3, and b is an integer having a value of from 0 to 2, provided, however, that the sum of a+b does not exceed 3.

The above compounds contain from one to three cationic hydrophilic groups per molecule, all attached to a single silicon atom. They are said to be useful for conventional siloxane applications and as surfactants. These compounds are prepared by reacting with a tertiary amine a silane corresponding to the structure

wherein Ar, R, R ¹ , X, n, a, and b are as defined supra.

SUMMARY OF THE INVENTION

Quaternary ammonium salts of cyclic siloxane polymers are prepared by

a. adding to an excess of water, compound (I):

wherein

X is Br, Cl, or I;

R ¹ is an alkyl group having from one to six carbon atoms;

R ² is an alkylene group having two or three carbon atoms;

R ³ is phenyl or benzyl or phenethyl or an alkyl group having from one to three carbon atoms;

R ⁴ is phenyl or benzyl or phenethyl or an alkyl group having from one to three carbon atoms;

R ⁵ is phenyl or benzyl or phenethyl or an alkyl group having from one to 18 carbon atoms;

R ⁶ is methyl or ethyl;

and the total number of [carbon atoms in R ¹ through R ⁵ ] per [silicon atom] does not exceed 28; and

b. redistributing the silicon-oxygen bonds to form the cyclic polymeric Compound (II):

wherein

n = an integer from about eight to about 20;

X is Br, Cl, or I;

and all other symbols are the same as those previously defined.

Compound (II) is useful as a surfactant, bactericide, and anticariogenic agent.

What is new includes compound I, compound II, and the process of preparing compound II from compound I.

DETAILS OF THE INVENTION

Compound II as defined in the summary has a unique combination of a cyclic siloxane "backbone" and a plurality of quaternary ammonium cationic hydrophilic groups. In water this compound forms micelles and anisotropic liquid-crystalline phases in the manner of ordinary surfactants.

The siloxane "backbone" is strongly hydrophobic, while the plural quaternary groups are strongly hydrophilic. The latter dominate to the extent that a degree of solubility in water is present. However, the former confers the property of high adsorption from a water solution upon hydrophobic surfaces such as oils and fibers, and overall the compound with both hydrophobic and hydrophilic moieties is highly surface active. Useful bactericidal properties are also present.

The structure of the surface-active compounds (II) of the instant invention is not only new but also substantially different from those hitherto known in the art. The silicone ring contributes significantly to the hydrophobic properties and the plurality of quaternary ammonium groups associated with the silicone ring exerts a distinct and unusual effect as described infra.

Preferred embodiments of compound II are those wherein:

n is an integer from about eight to about 20, averaging from about 12 to about 18;

X is Br;

R ¹ is methyl;

R ² is ethylene;

R ³ is benzyl or methyl;

R ⁴ is benzyl or methyl; and

R ⁵ is phenyl or benzyl or an alkyl group having from one to 18 carbon atoms.

Among these above-mentioned embodiments, especially preferred are those wherein R ³ is methyl and R ⁵ is benzyl or a normal alkyl group having from four to 12 carbon atoms.

Compound I as defined in the summary is useful as a chemical intermediate in the preparation of compound II. Preferred embodiments of compound I correspond exactly to those described in the two paragraphs immediately above.

The process defined in the summary also refers preferably to those embodiments of compounds I and II which are described as `preferred` in the paragraphs immediately above.

The complete synthesis of the compounds of this invention will be illustrated using, for the sake of clarity and simplicity, methyl derivatives. This is not intended to limit the practice of the invention, and it will be recognized by those skilled in the art that the higher alkyl, aryl, and alkyl/aryl derivatives discussed throughout the specification react in a manner which is altogether analogous.

The synthesis given below begins with simple, convenient, and commercially available raw materials. However, the processing steps involved in the preparation of compound I are known to those skilled in the art, and these steps are not a part of the instant invention.

Example 1

The entire sequence of reactions given below was conveniently carried out in a single batch vessel, with each successive reactant added in turn after the previous step had been completed. Commercially available hexamethyl disilazane was hydrolyzed in ether, with cooling, to produce trimethyl silanol:

The silanol was salted out with brine and the water was removed; then chunks of metallic sodium were added in excess to the silanol, which reacted to produce sodium trimethyl silanolate;

Unreacted sodium was then physically removed, and the silanolate was reacted with commercially available dichloromethyl vinyl silane to form bis(trimethylsiloxy) methyl vinyl silane: ##SPC1##

This compound was hydrobrominated under free radical conditions to form bis-(trimethyl siloxy)-methyl-2-bromoethylsilane:

For purposes of positive identification, the reaction product of equation (4) was washed with sodium bicarbonate solution, then with water, and dried over molecular sieves. A small amount of a separate phase consisting of polymeric silicones was discarded. The product was distilled at 0.1 mm., b.p. 127°-129° C. Analysis for [(CH ₃ ) ₃ SiO] ₂ Si(CH ₃ )CH ₂ CH ₂ Br was as follows:

Calculated Found ____________________________________________________________ ______________ elemental analysis: % C 32.8 32.8 % H 7.6 7.5 % Br 24.3 23.7 Mol. Wt. 329 344

infrared: Si--CH ₃ , Si--O--Si, and (CH ₃ ) ₃ --Si groups nuclear magnetic resonance (nmr):

τ9.8, indicative of Si--CH ₃ group

τ6.7, two protons (triplet), indicative of primary alkyl bromide

For purposes of continuing with the synthesis it was unnecessary to carry out this elaborate separation. It was sufficient merely to remove water and hexane from the preceding step and proceed directly to amination. The product at this stage was 90-95 percent pure as determined by gas-liquid chromatography.

The next step was to add trialkyl amine to this 90-95 percent pure bromosilane to form bis-(trimethyl siloxy)-methyl-2-(trimethyl ammonio)-ethyl silyl bromide. This is a specific embodiment of compound (I), and will be designated herein as compound (i). This step was carried out with a 1:1 molar ratio of reactants at 85° C. over a 4-5-hour period: ##SPC2##

Alternatively, and especially useful if the trialkyl amine of choice is not available, the bromosilane can be reacted with dialkyl amine first and then with an alkyl bromide to form exactly the same compound (i) formed by equation (5). ##SPC3##

The product, compound (i) which is a specific embodiment of compound (I) as defined in the summary, was a white hygroscopic solid. Infrared analysis indicated the presence of Si(CH ₃ ) ₃ groups. Yield was 75 percent of theory, based on the bromosilane.

The utility of compound (i), the bromide salt of bis-(trimethyl siloxy)-methyl-2-(trimethyl ammonio)-ethyl silane, is as a chemical intermediate in the preparation of cyclic surface-active silicone polymers which form upon hydrolysis with water.

Hitherto unsuspected lability of the siloxane linkages led to a redistribution of bonds with the formation of hexamethyl disiloxane plus a completely new silicone polymer which is a specific embodiment of compound (II) as defined in the summary and will be designated here as compound (ii). ##SPC4##

It is reiterated that variations in structure are permissible as detailed elsewhere in the specification and in the claims and that this particular compound is merely illustrative of the reactions that take place.

For purposes of identification, the reaction products of equation (7) were put into D ₂ O for nmr studies. It was noted that the majority of methyl protons in the τ9.8 region had been lost from the aqueous phase and that a second, oily, phase existed. Recovery of the dissolved sample by removal of the D ₂ O gave a product which exhibited frequencies for Si--CH ₃ and Si--O--Si in the infrared, but which totally lacked the Si(CH ₃ ) ₃ frequency (11.96 μ). The separating phase was found to be identical to an authentic sample of (CH ₃ ) ₃ Si--O--Si(CH ₃ ) ₃ by infrared and chemical methods.

Compound (ii) was subjected to elemental analysis and yielded the following results as compared with calculated values for this structure:

Calculated: % C--31.8; H--7.07; n--6.2; Br--35.4

Experimental: % C--31.6; H--7.5; N--6.4; Br--36.0

The structure of the monomer unit was therefore fully identified by both spectral and analytical data.

The cyclic nature of the compound was established, as pointed out supra, by the analytically determined total lack of end-capping --Si(CH ₃ ) ₃ groups. It remained to be determined the degree of polymerization of the cyclic compound; in particular, the degree of polymerization in aqueous solution. From a general knowledge of siloxane chemistry, it is believed that these polymers break up and reform in a state of dynamic equilibrium. No way of precise determination is known to the art. However, a method is available to determine the average number of monomer units per polymer unit in Glauber's salt, Na ₂ SO ₄ ^. 10H ₂ O. As described in Chem. Rev. 40, 159 (1947) this method, based on transition point lowering, gives especially good results because the freezing point varies linearly with concentration over a relatively wide range. The results of this determination indicated an "apparent molecular weight" of 212. Assuming complete dissociation of the quaternary ammonium group (i.e.,

a polymer having [degree of polymerization=n] would dissociate to n+1 particles.

The following relationship would then hold:

For the structure of compound (ii) and the experimental value of 212,

(226n)/(n+1)=212; n=15

The molecular weight of the polymeric compound (ii) is therefore 226×15=3,390. This characterizes the polymer as one of relatively low molecular weight in comparison with those polymers whose molecular weight runs into the hundreds of thousands. It is believed that the structure in water is similar, with an average molecular weight of about 3,000 to 4,000 for compound (ii). It is further believed that compound (ii) is composed of polymers having varying degrees of polymerization, i.e., n can be as low as about eight or as high as about 20, with an average of about 12 to about 18.

Discussion

Processing steps (1) through (6) supra represent a convenient way to prepare compound (i) from commercially available starting materials. However, other ways of preparing this compound are also known to those skilled in the art. For example

can be reacted with CH ₂ =CH=N(Me) ₃ , Br or alternatively with CH ₂ =CH Br followed by N (Me) ₃ to produce compound (i).

The bis-(trimethyl siloxy) ammonium compound (i) has been discovered to be particularly suited for redistribution of the siloxane linkages. First, the quaternary ammonium group renders the compound water soluble. Secondly, involvement of the trimethylsiloxy group in the redistribution process leads, via an intermediate trimethyl silanol moiety, to the insoluble hexamethyl disiloxane. (Trimethylsilanol was isolated from certain of the reaction mixtures.) The hexamethyl disiloxane removes itself from the reaction system, thereby displacing the equilibrium to the right in equation (7) as written supra.

The redistribution mechanism can be represented as

In an aqueous system the amphoteric water molecule in high concentration (approaching 55 M) can function either as an electrophile or as a nucleophile and thus assist in the formation of the silanol in acidic, basic, or neutral media.

The facility of redistribution is illustrated by examining the rate of redistribution as a function of pH. Samples of compound (i) were weighed under anhydrous conditions and dissolved in water at various pH's. Hexane was added to the solutions, which were vigorously stirred at room temperature. The hexane extracts were analyzed periodically (g.l.c.) for hexamethyldisiloxane as a measure of the completeness of the redistribution reaction with the following results:

pH time (min.) % reacted 3.5 18 82% 4.0 20 80% 6.0 22 81% 7 22 75% 7 30 100% 8.0 17 83% 9.0 19 80% 10.0 21 87%

The statements made supra about compound (ii) relating to varying degrees of polymerization are believed to apply equally well for compound (II) in general; i.e., to all analogous compounds within the contemplation of the invention. Similarly, statements made supra about compound (i) relating to alternative methods of preparation and ease of redistribution hold equally well for compound (I) in general; i.e., all analogous compounds within the scope of this invention.

Example 2

For the preparation of other embodiments of the invention, different disilazanes (equation 1), different unsaturated silanes (equation 3), different halogen acids (equation 4), and different amines (equations 5,6) can be employed in a manner well known to those skilled in the art to produce a whole series of bis-(trialkylsiloxy) ammonium compounds (I).

The process of the instant invention used to make the corresponding compounds (II) was as follows: the appropriate bis-(trialkylsiloxy) ammonium compound was dissolved in a 60-40 water-methanol mixture. 100 ml. of n-hexane was added, and the mixture stirred vigorously for 2 hours. The hexane layer was replaced with fresh hexane, which was then monitored by infrared for the formation of additional (CH ₃ ) ₆ Si ₂ O (none was even seen after 2 hours). The emulsions which formed in this step (when long-chain compounds were being prepared) were broken with methanol or ethanol. The water layer was evaporated to yield a semisolid, yellowish mass. This was dissolved in methanol and decolorized with carbon. The methanol was stripped and the resulting material dried over P ₂ O ₅ in the vacuum desiccator. The resulting compounds were extremely deliquescent, and all operations and transfers were done in a dry-bag, over P ₂ O ₅ . Sample phials for analytical samples were flamed out to assure dryness and sealed with paraffin. The following compounds were prepared: ##SPC5##

The redistribution by which the compound of example 2-b was prepared was examined over the pH range 3.5 to 10. Redistribution was about 80 percent complete in about 20 minutes in every case.

Example 3

Other embodiments of the invention are as follows:

a. Replacement of dichloromethyl vinyl silane with dichloro-n-butyl-vinyl silane in equation (3) leads to the compound ##SPC6##

b. Replacement of dichloromethyl vinyl silane with dichloro-n-hexyl-vinyl silane in equation (3) leads to the compound ##SPC7##

c. Replacement of HBr in equation (4) by HCl leads to the quaternary chloride salt

n [(CH ₃ ) ₃ Si O] ₂ Si (CH ₃ ) CH ₂ CH ₂ N (CH ₃ ) ₃ , Cl

which redistributes to the compound

d. Replacement of HBr in equation (4) by HI leads to iodide salts analogous to the chloride salts of example 3c.

e. Replacement of the vinyl silane in equation (3) by the corresponding allyl silane leads to

n [(CH ₃ ) ₃ Si O] ₂ Si (CH ₃ ) CH ₂ CH ₂ CH ₂ N (CH ₃ ) ₃ , Br

which redistributes to

f. Use of tribenzyl amine instead of trimethyl amine in equation (5) leads to

n [(CH ₃ ) ₃ Si O] ₂ Si (CH ₃ ) CH ₂ CH ₂ N (CH ₂ C ₆ H ₅ ) ₃ , Br

which redistributes to

g. Use of triphenyl amine instead of trimethyl amine in equation (5) leads to

n [(CH ₃ ) ₃ Si O] ₂ Si (CH ₃ ) CH ₂ CH ₂ N (C ₆ H ₅ ) ₃ , Br

which redistributes to

h. Use of triphenethyl amine instead of trimethyl amine in equation (5) leads to

n [(CH ₃ ) ₃ Si O] ₂ Si (CH ₃ ) CH ₂ CH ₂ N (C ₂ H ₄ C ₆ H ₅ ) ₃ , Br

which redistributes to

i. Use of triethyl or tripropyl amines instead of trimethyl amine in equation (5) leads to analogous compounds with three ethyl or propyl groups on the nitrogen atom.

j. Replacement of the hexamethyl disilazane with hexaethyl disilazane in equation (1) leads to

n [(CH ₃ CH ₂ ) ₃ Si O] ₂ Si (CH ₃ ) CH ₂ CH ₂ N (CH ₃ ) ₃ , Br

which redistributes to compound (i) exactly but which forms hexaethyl disiloxane instead of the hexamethyldisiloxane shown in equation (7).

k. Use of octadecyl bromide instead of methyl bromide in equation (6) leads to ##SPC8##

l. The various modifications discussed in the preceding paragraphs can readily be combined. The only additional limitation is that the number of carbon atoms per silicon atom in all compounds I must not exceed 28. For example, following the teachings of paragraphs (a), (c), (e), and (f) results in the compound ##SPC9##

Each of these polymeric compounds formed by redistribution in water possesses surface activity and bactericidal properties.

UTILITY

It was stated supra that the usefulness of compound I is as a chemical intermediate in the preparation of the polymeric compound II. Compound II is useful as a cationic surfactant, as a bactericide, and as an anticariogenic agent.

To evaluate utility as a cationic surfactant in aqueous medium, two important parameters of surface activity were measured and are given in table I for three embodiments of the instant invention as compared with two quaternary ammonium cationics based on a conventional hydrocarbon chain. ##SPC10##

It can be readily noted that the compounds of the instant invention wherein R ⁵ is a long-chain hydrocarbon exhibit strikingly low c.m.c.'s and surface tensions as contrasted to those of conventional hydrocarbon cationic surfactants. This provides a very high level of surface activity at very low concentrations of the quaternized siloxane polymer. Indeed it is rare to find surface tensions below about 25 for any surface-active compound--cationic, anionic, or nonionic--at any concentration. These spectacular surface-active properties provide excellent wetting, spreading, and penetrating characteristics and are useful in cleaning hard surfaces such as walls, floors, glassware and metal parts; in laundering soiled fabrics; in dyebaths; desizing; and similar industrial and consumer surfactant applications.

By way of illustration of the phase properties of the compounds of the instant invention, the compound of example 2-d (the dodecyl derivative) was studied as a function of temperature and concentration in water, and the results are given in the accompanying drawing.

Region A thereon is an isotropic phase. The quaternary siloxane polymer is completely soluble in water macroscopically, and the solution is single phase so far as the phase rule is concerned; micelles however are present above the c.m.c. which for this compound means above 0.016 percent as described above.

Region B is an anisotropic, mesomorphic, liquid crystalline phase. More particularly it is a "neat" phase as described in the art. In this configuration the surfactant molecules are aligned layer by layer throughout the material in ordered sheets.

Region C is a two-phase region wherein crystals of the quaternary siloxane polymer and layers of mesomorphic neat phase coexist in equilibrium.

Further details on the subject of phase behavior of surface-active compounds may be found in many references: among them are McBain et al., J.A.C.S. 60, 1866 (1938); Luzzati et al., Nature 180, 600 (1957), and Smith, International Science & Technology, p. 74, Jan. 1967.

The foregoing has described the use of the compounds of the instant invention as cationic surfactants. A second utility is as bactericides. Bactericidal assay was carried out by determining the percent kill of typical organisms by exposing a suspension of bacteria to the test compound, removing aliquots of the treated suspension at a specified time interval, inoculating into 5-percent horse serum, plating in nutrient sugar, incubating for 48 hours, and noting the number of bacterial colonies that develop.

Specifically, this series of tests was carried out by determining the percent kill of Staphylococcus aureus FDA 209 (a Gram positive organism) and Escherichia coli (a Gram negative organism) with an exposure time of 10 minutes to the test compounds at a concentration of 100 parts per million. The suspending medium was FDA nutrient broth and the inoculum size was approximately 250×10 ⁶ cells/ml. One ml. of the suspension was transferred after 10 minutes of contact into 100 ml. of sterile horse serum in distilled water. Additional dilutions were made as necessary to get the number of colonies per plate into a countable range. The dilutions were placed in nutrient agar and incubated at 37° C. for 48 hours. Colonies were then counted and the percent reduction in viable count was determined in relation to a colony count attained by plating the inoculated broth without an active agent. A commonly used quaternary ammonium bactericidal agent, dimethyl dodecyl benzyl ammonium chloride, was used as a standard of comparison.

The following table presents bactericidal data and shows that the compounds of the instant invention are effective bactericidal agents against E. coli and highly effective against S. aureus. ##SPC11##

Still another utility of the compounds of the instant invention is as an anticariogenic agent. Table III gives in vitro test results for samples of calcium phosphate (apatite which constitutes the bulk of dental enamel is a form of calcium phosphate) treated with some of the compounds of the instant invention and subjected to standard acid rinses, following which the resultant solutions were analyzed for phosphate ion concentration as a measure of solubilization. In each case the treatment with quaternary siloxane polymer reduced the amount of calcium phosphate solubilized by the acid. It is believed that the siloxane polymer adsorbs on the calcium phosphate to form a film which decreases the rate of acid solubilization. Procedural details of the test are as follows:

The "sequential exposure" tests were conducted by exposing 0.20±0.05 g. of calcium phosphate [sieved to pass 100 percent through 100 U.S. mesh and 100 percent on 325 U.S. mesh] to a 5 percent solution of the quaternary siloxane polymer for 3 minutes. The solution was removed by filtration and the calcium phosphate was rinsed with two 10 ml. portions of water. The calcium phosphate was thence treated with vigorous stirring with 15 ml. of 0.10 N acetic acid adjusted to pH 5.0 with 12 N sodium hydroxide. The data given in table III define the phosphate content of the acid rinse solution after varying times of exposure to the solid calcium phosphate.

The "untreated" test was conducted in like manner except the exposure to the quaternary siloxane polymer was omitted. The "concurrent exposure" test was conducted by treating the calcium phosphate with a 15 ml. solution 0.10 N in acetic acid at pH 5.0 which also contained 5-percent quaternary siloxane polymer. ##SPC12##

It is apparent that a substantial decrease in acid solubilization is accomplished by every method of running the test with the compounds of the instant invention.

The preceding in vitro test was supplemented by an in vivo test in the rat. Compounds (II) having the structures given in examples 1 and 2b were tested at 0.1-percent concentration using rats on a cariogenic diet.

Test procedure was as follows:

The compositions to be tested were applied to the teeth of weanling Sprague-Dawley strain rats with a small cotton swab. The animals were housed individually and were placed immediately on a fine particle cariogenic diet comprised of 32-percent nonfat dry milk, 63-percent sucrose, 2-percent dried liver extract, and 3-percent Celluflour (trademark). Water and food were administered ad libitum through the course of the experiment. The test compositions were assigned at random to one member of each of 20 litters, sex random. The test and control materials were topically applied twice daily for 14 days during a 3-week experimental period. At the end of the treatment periods, all animals were sacrificed and their teeth stained with 2-percent AgNO ₃ to disclose the carious lesions. The heads of the animals were then autoclaved to obtain the clean, stained, teeth and jawbone. The teeth were sectioned and examined microscopically and the individual carious lesions were graded using the method of Francis described in "The Effectiveness of Anticaries Agents in Rats Using an Incipient Carious Lesion Method," Arch. Oral Biol., Vol. 11, 141-148 (1966). At the conclusion of the experiment, the number of lesions and severity score for each group were averaged and a percent reduction in caries based on the controls was calculated. The concentration of active agent and percent reduction in caries score are set forth in table IV. ##SPC13##

Results above show that the tooth surfaces were rendered less susceptible to caries incidence when treated with a film-forming quaternary siloxane polymer deposited from an aqueous solution.