WO1995026371A1

WO1995026371A1 - Intermediates for the preparation of poly(cyanoacrylates) and applications of the poly(cyanoacrylates) so prepared

Info

Publication number: WO1995026371A1
Application number: PCT/IE1994/000018
Authority: WO
Inventors: Valery Alexandrovich Dyatlov; Viktor Maleev
Original assignee: Patrique Limited
Priority date: 1994-03-28
Filing date: 1994-03-28
Publication date: 1995-10-05
Also published as: AU6289794A

Abstract

A process is provided for the reversible coupling of weak nucleophiles to the carbon-carbon double bond of 2-cyanoacrylic acid or an ester thereof so as to reversibly protect the bond. Examples of weak nucleophiles include alcohols (including diols and polyols), phenols, sulfur nucleophiles such as thiols and thio acids, phosphorus nucleophiles such as dialkyl or diarylphosphites and phosphines, and carbon nucleophiles such as active methylene compounds. The process involves reacting 2-cyanoacrylic acid or an ester thereof with the weak nucleophile in the presence of an inert solvent under polymerisation inhibiting conditions and in the presence of an acidic catalyst. The compounds produced can be used as intermediates for the preparation of poly(cyanoacrylates), following elimination of the nucleophile added to give a 2-cyanoacrylate monomer which then polymerizes. The poly(cyanoacrylates) thereby produced have many applications, for example, in the preparation of films such as single- or multi-layer Langmuir-Blodgett films.

Description

Intermediates for the preparation of poly(cyanoacrylates) and applications of the poly(cyanoacrylates) so prepared

Technical Field

This invention relates to the reversible coupling of a weak nucleophile to the carbon-carbon double bond of 2-cyanoacrylic acid or an ester thereof, so as to reversibly protect said bond.

Background Art

Esters of 2-cyanoacrylic acid having the general formula:

are widely used as monomers for the preparation of polymers and copolymers. The ability of 2-cyanoacrylic acid esters to polymerise rapidly under the influence of moisture or nucleophilic substances has led to their exploitation as instantaneous adhesives. Thus, cyanoacrylate esters are the main constituents of the rapid-bonding adhesives commonly known as "superglues". Bonding results from the conversion of a low-viscosity monomer into a solid polymer by anionic polymerisation. Esters of 2-cyanoacrylic acid are also used for the preparation of poly(alkyl 2-cyanoacrylate) nanoparticles and nanocapsules which may be employed as carrier or delivery systems for drugs or other active agents. Furthermore, esters of 2- cyanoacrylic acid can be used to prepare Langmuir-Blodgett type thin films which may be applied as coatings for components used in the electronics industry.

The inherent ability of 2-cyanoacrylic acid esters to undergo rapid anionic polymerisation causes complications as regards their synthesis, chemical modification, and storage. It is necessary to be able to control the rate of polymerisation of cyanoacrylate monomers in order to permit their successful manipulation prior to carrying out the bonding process. Additionally, there is a need to be able to control the surface-active properties of cyanoacrylate monomers which are to be utilised in Langmuir-Blodgett film applications.

The principal method known for the regulation of the chemical and physical properties of 2-cyanoacrylate monomers and polymers is by variation of the structure of the ester moiety. However, opportunities for the chemical modification of simple cyanoacrylate esters in order to prepare new monomers are limited due to the high chemical reactivity of the carbon-carbon double bond.

Methods for the synthesis of 2-cyanoacrylic acid ester monomers are few in number. An important commercial route to these compounds is the Knoevenagel Condensation Method (H. Lee (Ed.) (1981), "Cyanoacrylic Resins - The Instant Adhesives", Pasadena Technology Press, Pasadena, U.S.A.). According to the Knoevenagel method a cyanoacetic acid ester and formaldehyde are reacted together in the presence of an amine to give alkyl cyanoacrylate oligomers. The free cyanoacrylate ester monomer is then generated by thermally cracking the oligomer and vacuum distilling the monomer on to an acidic stabihser. The Knoevenagel method is limited to the preparation of alkyl 2-cyanoacrylates which have an alkyl moiety of no more than ten carbon atoms. Above this limit, the monomers cease to be distillable at temperatures which are below their respective thermal destruction temperatures. In fact, n-octyl 2- cyanoacrylate is the monomer with the greatest number of carbon atoms in the ester function that has been reported to have been prepared by the Knoevenagel method (Kublin, K.S. and Miguel, F.M., (1970), J. Amer. Vet. Ass., Vol. 156, No. 3, 313-318; Alco, J.J. and DeRenzis, F.A., (1971), J. Pharmacol. Ther. Dent., Vol. 1, No. 3, 129-132).

Short chain (less than ten carbon atoms) alkyl 2-cyanoacrylates with polar groups such as hydroxyl, carboxyl and ester groups, and aryl cyanoacrylates cannot generally be prepared by the Knoevenagel Condensation Method because of their high boiling points.

Another method for the preparation of alkyl 2-cyanoacrylic acid esters is based on the transesterification reaction (Voitekunas, J., Polyakova, A.M., Mager, K.A., Kokhanov, Yu. V. and Voitkov, A.I., U.S.S.R. Patent No. 726,086). This single-stage method involves the transesterification of methyl or ethyl 2-cyanoacrylate with a higher alcohol under acid-catalysed conditions. Because of the relatively low efficiency of the process it is necessary to separate residual methyl or ethyl 2- cyanoacrylate from the product ester by vacuum distillation.

A method for the synthesis of 2-cyanoacrylic acid esters involving prior protection of the carbon-carbon double bond of a simple cyanoacrylate derivative is described in U.S. Patent No. 3,903,055. The method can involve three or five steps. In the five- step process, ethyl or isobutyl 2-cyanoacrylate is reacted with anthracene to form its stable Diels-Alder anthracene adduct. Basic hydrolysis of the ester function in the adduct gives the corresponding carboxylic acid salt from which the free acid is obtained upon acidification. The carboxylic acid is next converted into its acid chloride with thionyl chloride, and this is reacted with an alcohol to give a new ester. A displacement reaction involving the stronger dienophile maleic anhydride is then carried out to give the product cyanoacrylate ester together with the anthracene-maleic anhydride Diels-Alder adduct from which it must be separated. The cyanoacrylate ester formed can then be used as a monomer for the preparation of poly(alkyl 2-cyanoacrylates). It should be noted that this route to alkyl 2-cyanoacrylates is purely a laboratory method, and that it has not proved practicable on a larger scale.

Patent Publication JP 91 065340 describes a route to the cyanohydrins of pyruvic acid and its esters which can be used as intermediates for the preparation of 2-cyanoacrylate esters. Patent Publication JP 91 075538 describes 1-acetoxy-l- cyanopropionic acid esters which can be converted into 2-cyanoacrylate esters by thermal elimination of a molecule of acetic acid.

As mentioned supra, some of the physical properties of alkyl 2- cyanoacrylate monomers can be regulated by the preparation of monomers wherein the chemical structure of the ester moiety has been modified.

Modification of the ester moiety has been used as a means of controlling the surface-active properties, hydrophobicities, and solubilities of cyanoacrylate esters (Leonard, F., Collins, J.A. and Porter, H.J., (1966), J. Appl. Polym. Sci., Vol. 10, No. 11, 1617- 1623).

Long-chain 2-cyanoacrylate esters have been used for the formation of Langmuir-Blodgett films (Matveeva, N.K., Pasekov, V.F. and Savel'eva, L.V., (1991), Mikroelectronika (Akad. Nauk S.S.S.R.), Vol. 20, No. 5, 501-503).

The solubility of cyanoacrylate esters in aqueous media is a function of the esterifying radical. A decrease in solubility is achieved by lengthening the alkyl chain.

Some control over the properties of alkyl 2-cyanoacrylates can thus be achieved by varying the nature of the esterifying group. However, these changes may lead to polymers which do not have desirable characteristics. Thus, for example, use of butyl 2- cyanoacrylate in an adhesive composition instead of methyl 2- cyanoacrylate may lead to a more manageable rate of polymerisation but will cause a significant decrease in the strength of the bond which is formed.

It will be appreciated, therefore, that control of the properties of a 2-cyanoacrylate monomer by variation of the nature of the esterifying group without at the same time influencing the properties of the derived polymer is not possible at present.

Accordingly, for the above reasons, a method for the modification of the physical and chemical properties of conventional and other alkyl 2-cyanoacrylate monomers which does not affect the properties of the polymers obtained therefrom is highly desirable.

The synthesis of ethyl 3-methoxy-2-cyanopropionate via reaction of the sodium salt of ethyl cyanoacetate with chloromethyl methyl ether has been described (Foldi, Z., v. Fodor, G., Demjen, L, Szekeres, H. and Halmos, I, Berichte, 1942, Vol. 75, No. 7, 755-763). The same ethyl 3-methoxy-2-cyanopropionate was prepared by an almost identical method in U.S. Patent No. 2,467,926 but was not isolated or characterised. No other 3-alkoxy-2-cyanopropionic acid derivatives have been reported, and this is not surprising since the chloromethyl alkyl ethers required for their synthesis as described supra are usually hazardous and unpleasant materials.

Some products resulting from the addition of nucleophiles to the carbon-carbon double bond of 2-cyanoacrylates have been described.

Organosilanes have been added to 2-cyanoacrylic acid and esters thereof with formation of the corresponding saturated products

(Kolomnikova, G.D., Prihodchenko, Yu. D. and Gololobov, Yu. G., Izv. R. Akad. Nauk, Ser. Khim., 1992, No. 7, 1655-1657).

Thiols and thioacetic acid can be added to ethyl 2-cyanoacrylate to yield ethyl 2-cyano-3-thioalkylpropionates and ethyl 2-cyano-3- acetylthiopropionatc, respectively (Kandror, I.I., Bragina, I.O.,

Galkina, M.A. and Gololobov, Yu. G., Izv. Akad. Naul S.S.S.R., Ser. Khim., 1990, No. 12, 2798-2801 : ibid., 15th International Symposium on the organic Chemistry of Sulfur, Caen, France, 1992).

Thiourea has been added to ethyl 2-cyanoacrylate in the presence of trifluoroacetic acid to give the corresponding saturated S-alkylthiouronium trifluoroacetate (Kolomnikova, Yu. D., Krilova, T.O., Chernoglasova, I.V., Petrovsky, P.V. and Gololobov, Yu. G., Izv. Russ. Akad. Nauk, Ser. Khim., (1993), No. 7, 1245).

Dialkyl and diaryl phosphites have been added to 2-cyanoacrylic acid and its ethyl ester to give dialkyl and diaryl phosphonates

(Kolomnikova, G.D., Prihodchenko, Yu. D., Petrovsky, P.V. and Gololobov, Yu. G., Izv. R. Akad. Nauk, Ser. Khim., 1992, No. 8, 1913).

Triethyl phosphite has been added to 2-cyanoacrylic acid to yield the derived 3-(diethylphosphono)propionic acid (Kandror, LI.,

Lavrykhin, B.D., Bragina, I.O., Galkina, M.A. and Gololobov, Yu. G., J. Obsch. Khim., (1990), Vol. 6, No. 9, 2160-2168), and to ethyl 2- cyanoacrylate to give ethyl 2-cyano-3-(diethylphosphono)propionate (Kandror, I.I., et al. (1990) supra).

Diethyl chlorophosphite and chlorodiphenylphosphine react with ethyl 2-cyanoacrylate in the presence of trifluoroacetic acid to give, respectively, ethyl 2-cyano-3-(diethylphosphono)propionate and ethyl 2-cyano-3-(diphenylphosphinoxy)propionate (Kolomnikova, Yu. D. et al. (1993) supra). Catechyl chlorophosphite reacts similarly with ethyl 2-cyanoacrylate to give the derived catechylphosphonate derivative (Kolomnikova, Yu. D. et al. (1993) supra).

Triphenylphosphine reacts with ethyl 2-cyanoacrylate under trifluoroacetic acid catalysis to give ethyl 2-cyano-3- (triphenylphosphonium)propionate trifluoroacetate (Kolomnikova, Yu. D. et al. (1993) supra).

Phosphorus-sulfenyl chlorides have been added to 2- cyanoacrylates with formation of the corresponding thiophosphonates (Kolomnikova, G.D., Krilova, T.O. and Gololobov, Yu. G., J. Obsch. Khim., 1993, Vol. 63, No. 3, 716). Carbon nucleophiles derived from active methylene compounds such as methyl nitroacetate, diethyl malonate and ethyl cyanoacetate have been reacted with ethyl 2-cyanoacrylate to give the expected Michael adducts (Kandror, LI., Bragina, I.O., Galkina, M.A., Belokon, Yu. N., Lavrykhin, B.D. and Gololobov, Yu. N., Izv. Russ. Akad. Nauk, Ser. Khim., (1992) No. 10, 2449-2453).

None of the compounds mentioned supra have been used for the reversible protection of the carbon-carbon double bond of 2- cyanoacrylates, and conditions for effecting the reverse Michael reactions needed for their conversion into monomeric 2-cyanoacrylates or into poly(2-cyanoacrylates) have not been described.

Disclosure of Invention

The invention provides in a first aspect a process for the reversible couphng of a weak nucleophile to the carbon-carbon double bond of 2-cyanoacrylic acid or an ester thereof, so as to reversibly protect said bond, which comprises reacting 2-cyanoacrylic acid or an ester thereof with said weak nucleophile in the presence of an inert solvent under polymerisation inhibiting conditions and in the presence of an acidic catalyst.

The weak nucleophile can be an alcohol or a phenol.

The term alcohol as used herein includes diols and polyols.

The weak nucleophile can also be selected from:

i) a thiol, thiophenol, a thioamide, a thio or dithio acid or other thionucleophile;

ii) a dialkyl or diarylphosphite, a dialkyl or diarylthiophosphite, a phosphine, phosphorus sulfenyl halide or other phosphorus nucleophile; and iii) a carbon acid

as hereinafter described.

This first aspect of the invention thus provides a method for the reversible protection of the chemically reactive carbon-carbon double bond of polymerisable alkyl or aryl 2-cyanoacrylates whereby a weak nucleophile added across the double bond can be eliminated under the conditions of base-initiated anionic polymerisation to yield poly(alkyl or aryl 2-cyanoacrylates) together with the relevant weak nucleophile.

The acidic catalyst is suitably a non-volatile acid such as an aliphatic sulfonic acid or an aromatic sulfonic acid. Accordingly, the non- volatile acid is suitably methane sulfonic acid or p -toluenesulfonic acid.

Alternatively, the acid catalyst can be a carboxylic acid.

An essential feature of the acid catalyst is that it does not react with the alcohol or phenol or other weak nucleophile being used.

Preferably, the process is carried out under conditions which inhibit anionic polymerisation.

Further, preferably, the process is carried out in the presence of a weak acid.

Suitably the weak acid is sulfur dioxide.

Preferably, when the weak acid is sulfur dioxide, gaseous sulfur dioxide is bubbled into the reaction mixture as a continuous stream.

The anionic polymerisation inhibitor can be an aliphatic sulfonic acid, an aromatic sulfonic acid or carbon dioxide. Further, preferably, the process according to the invention is carried out in the presence of a free radical polymerisation inhibitor.

Suitably the free radical polymerisation inhibitor is benzoquinone, hydroquinone, methylhydroquinone or naphthoquinone.

Preferably the inert solvent is benzene, toluene, xylene, hexane or a chlorinated hydrocarbon.

The process according to the invention is suitably carried out at a temperature in the range 20-200°C, more especially in the range 80- 100°C.

When secondary alcohols or phenols are being reacted in accordance with the invention, irrespective of whether 2-cyanoacrylic acid or an ester thereof is used, preferably the reaction is carried out in the presence of sulfur dioxide to optimize conditions, because of the tendency of cyanoacrylate monomers to polymerise under the reaction conditions.

When 2-cyanoacrylic acid is used as a starting compound in accordance with the invention to prepare a 3-alkoxy-2-cyanopropionic acid ester, the water produced is continually removed by azeotropic distillation.

Preferably, the total volume of the reaction solvent is kept constant.

Further, preferably, when an alcohol or phenol is used as the weak nucleophile, said alcohol or phenol is added gradually to the reaction mixture.

According to a second aspect of the invention there is provided a process for the preparation of a compound of the general formula (I):

wherein Rl is: i) C_\ or higher saturated, optionally mono- or polysubstituted, linear or branched alkyl;

ii) C5 or higher saturated, optionally mono- or polysubstituted cycloalkyl or poly(cycloalkyl);

iii) C3 or higher, optionally mono- or polysubstituted, linear or branched alkenyl;

iv) C3 or higher, optionally mono- or polysubstituted, linear or branched alkynyl; or

v) a phenyl or optionally mono- or polysubstituted phenyl group,

and R² is: i) a hydrogen atom;

ii) Ci or higher saturated, optionally mono- or polysubstituted, linear or branched alkyl;

iii) C5 or higher saturated, optionally mono- or polysubstituted cycloalkyl or poly (cycloalkyl);

iv) C3 or higher, optionally mono- or polysubstituted, linear or branched alkenyl;

v) C3 or higher, optionally mono- or polysubstituted, linear or branched alkynyl;

vi) a phenyl or optionally mono- or polysubstituted phenyl group; or vii) a mono- or polysubstituted biphenyl, naphthyl or other cyclic or polycyclic aromatic or heteroaromatic group.

which comprises reacting 2-cyanoacrylic acid or an ester thereof with an alcohol or phenol in the presence of an inert solvent under polymerisation inhibiting conditions and in the presence of an acidic catalyst.

The following scheme depicts the reactions involved in the process according to the second aspect of the invention hereinabove described:

wherein R¹ and R² are as hereinabove defined.

In accordance with the second aspect of the invention, there is produced 3-alkoxy- and 3-aryloxy-2-cyanopropionic acids and esters thereof which may be employed as precursors to useful polymerisable 2-cyanoacrylic acid esters, said precursors having desirable chemical and physical properties. Thus, the invention provides a compound of the general formula (Ia):

wherein Rl is: i) a methyl group;

ii) C2 or higher saturated, optionally mono- or polysubstituted, linear or branched alkyl;

v) C3 or higher, optionally mono- or polysubstituted, linear or branched alkynyl; or

vi) a phenyl or optionally mono- or polysubstituted phenyl group,

and R² is: i) a hydrogen atom;

ii) Ci, optionally mono- substituted, alkyl;

iii) C2 saturated alkyl except when Rl is methyl;

iv) C2 saturated, mono- or polysubstituted alkyl;

v) C3 or higher saturated, optionally mono- or polysubstituted, linear or branched alkyl; vi) C5 or higher saturated, optionally mono- or .. polysubstituted cycloalkyl or poly (cycloalkyl);

vii) C3 or higher, optionally mono- or polysubstituted, linear or branched alkenyl;

viii) C3 or higher, optionally mono- or polysubstituted, linear or branched alkynyl;

ix) a phenyl or optionally mono- or polysubstituted phenyl group; or

x) a mono- or polysubstituted biphenyl, naphthyl or other cyclic or poly cyclic aromatic or heteroaromatic group.

Functional groups which are representative of those which would normally be used to substitute an R or R² group as hereinabove defined include but are not limited to halogen, carboxyl, nitrile, acylamino and heteroelement-containing groups.

In accordance with a third aspect of the invention the weak nucleophile can be a sulfhydryl group as found, for example, in a thiol, a thio acid or a dithio acid. This provides a further method for the reversible protection of the chemically reactive carbon-carbon double bond of polymerisable alkyl or aryl 2-cyanoacrylates whereby a thio compound added across the double bond can be eliminated under the conditions of base-catalysed anionic polymerisation to yield poly(alkyl or aryl 2-cyanoacrylates) together with the relevant thio compound.

The process according to the third aspect of the invention can be used for the preparation of a compound of the general formula (II) and its subsequent conversion into a 2-cyanoacrylate polymer

wherein R³ is: i) Cj or higher saturated, optionally mono- or polysubstituted, hnear or branched alkyl or cycloalkyl;

ii) C3 or higher, optionally mono- or polysubstituted Hnear or branched alkenyl or alkynyl;

iii) a phenyl or optionally mono- or polysubstituted phenyl group;

iv) a mono- or polysubstituted biphenyl, naphthyl or other cyclic or polycyclic aromatic or heteroaromatic group;

v) an acyl or thioacyl group;

vi) a dialkyl- or diarylphosphonyl group; or

vii) a dialkyl- or diarylthiophosphonyl group,

and R⁴ is: i) a hydrogen atom;

ii) Ci or higher saturated, optionally mono- or polysubstituted, hnear or branched alkyl;

iv) C3 or higher, optionally mono- or polysubstituted linear or branched alkenyl; v) C3 or higher, optionally mono- or polysubstituted hnear or branched alkynyl;

vi) a phenyl or optionally mono- or polysubstituted phenyl group; or

vii) a mono- or polysubstituted biphenyl, naphthyl or other cyclic or polycyclic aromatic or heteroaromatic group,

which comprises reacting 2-cyanoacrylic acid or an ester thereof with a sulfhydryl compound in the presence of an inert solvent under polymerisation inhibiting conditions and in the presence of an acidic catalyst under the conditions hereinabove defined followed by elimination of the sulfhydryl addend to give a 2-cyanoacrylate monomer which then polymerises.

Alternatively, the sulfhydryl compound itself can act as the acidic catalyst.

The following scheme depicts the reactions involved in the process according to the third aspect of the invention:

wherein R³ and R⁴ are as hereinabove defined. In this third aspect of the invention there is provided 3-thioalkyl-, 3-thioaryl-, 3-thioacyl-, 3-dithioacyl-, 3-thiophosphoryl- and 3-dithiophosphoryl-2-cyanopropionic acids and esters thereof which may be employed as precursors to useful polymerisable 2- cyanoacrylic acid esters.

Thus the invention provides a compound of the general formula (Ha):

wherein R³ is: i) C_\ optionally monosubstituted alkyl wherein the substituent is not a free carboxyl group whenever R⁴ is an ethyl group;

ii) C2 optionally mono- or polysubstituted saturated alkyl wherein the or each substituent is not a primary amino group or a hydroxyl group whenever R⁴ is an ethyl group, or wherein the substituents do not include a primary amino group and a free carboxy group attached to the same carbon atom whenever R⁴ is an ethyl group, or wherein the β-substituent is not another sulfur atom bearing a 2'-carboxy-2'-cyanoethyl function as the free carboxylic acid or as its ethyl or allyl ester whenever the substituent R⁴ is, respectively, a hydrogen atom, an ethyl group or an allyl group;

iii) C3 hnear or branched, optionally mono- or polysubstituted saturated alkyl;

iv) C4 hnear or branched, optionally mono- or polysubstituted saturated alkyl wherein the mono- substituent is not a hydrogen atom whenever R⁴ is an ethyl group;

v) C5 or higher linear or branched, optionally mono- or polysubstituted saturated alkyl or cycloalkyl;

vi) C3 or higher, optionally mono- or polysubstituted hnear or branched alkenyl;

vii) C3 or higher, optionally mono- or polysubstituted hnear or branched alkynyl,

viii) an unsubstituted phenyl group whenever R⁴ is not an ethyl group;

ix) a mono- or polysubstituted phenyl group;

x) a mono- or polysubstituted biphenyl, naphthyl or other polycyclic aromatic or heteroaromatic group,

xi) an acyl group other than acetyl except when R⁴ is other than an ethyl group when R³ may then be any acyl group;

xii) a thioacyl group;

xiii) a dialkyl or diaryl phosphonyl group excluding diethyl phosphonyl whenever R⁴ is an ethyl group;

xiv) a dialkyl or diaryl thiophosphonyl group excluding diethyl thiophosphonyl when R⁴ is an ethyl group,

and including sulfoxides and sulfones derived from any of i) - x) above, and R⁴ is: i) a hydrogen atom;

ii) Ci or higher, hnear or branched optionally mono- or polysubstituted saturated alkyl;

iv) C3 or higher, optionally mono- or polysubstituted hnear or branched alkenyl;

v) C3 or higher, optionally mono- or polysubstituted linear or branched alkynyl;

vi) a phenyl or optionally mono- or polysubstituted phenyl group; or

vii) a mono- or polysubstituted biphenyl, naphthyl or other cyclic or polycyclic aromatic or heteroaromatic group.

In accordance with a fourth aspect of the invention the weak nucleophile can be a dialkyl or diaryl phosphite, a dialkyl or diaryl thiophosphite, a phosphine or other phosphorus nucleophile. This aspect of the invention provides another method for the reversible protection of the chemically reactive carbon-carbon double bond of polymerisable alkyl or aryl 2-cyanoacrylates as outlined supra.

The process according to the fourth aspect invention can be used for the preparation of a compound of the general formula (III) and its subsequent conversion into a 2-cyanoacrylate polymer:

wherein R⁵ is: i) Ci or higher linear or branched saturated alkyl;

ii) C5 or higher cycloalkyl; or

iii) a phenyl or optionally mono- or polysubstituted phenyl group,

and R⁶ is: i) a hydrogen atom;

v) C3 or higher, optionally mono- or polysubstituted hnear or branched alkynyl;

vi) a phenyl or optionally mono- or polysubstituted phenyl group; or

vii) a mono-or polysubstituted biphenyl, naphthyl or other cyclic or polycyclic aromatic or heteroaromatic group,

and X is: i) an oxygen atom; or ii) a sulfur atom;

which comprises reacting 2-cyanoacrylic acid or an ester thereof with a phosphite or thiophosphite in the presence of an inert solvent under polymerisation inhibiting conditions and in the presence of an acidic catalyst under the conditions outlined hereinabove defined followed by ehmination of the addend to give a 2-cyanoacrylate monomer which then polymerises.

Alternatively, the phosphite or thiophosphite itself can act as the acidic catalyst.

The following scheme depicts the reactions involved in the process according to this aspect of the invention:

wherein R⁵ and R⁶ are as hereinabove defined.

In this fourth aspect of the invention there is provided 2-cyano- 3-(dialkylphosphono)-, 2-cyano-3-(diarylphosphono)-, 2-cyano-3- (dialkylthiophosphono)- and 2-cyano-3-(diarylthiophosphono)- propionic acids and esters thereof which may be employed as precursors to useful polymerisable 2-cyanoacrylic acid esters.

Thus the invention provides a compound of the general formula (Ilia):

wherein R⁵ is: i) a methyl group;

ii) an ethyl group except when R⁶ is an ethyl group or a hydrogen atom;

iii) a propyl group or substituted propyl group;

iv) an isopropyl group except when R⁶ is an ethyl group or a hydrogen atom and when X is an oxygen atom;

v) C4 or higher saturated, optionally mono- or polysubstituted linear or branched alkyl;

vi) a cyclohexyl group;

vii) an unsubstituted phenyl group except when R⁶ is an ethyl group or a hydrogen atom and when X is an oxygen atom; viii) a mono- or polysubstituted phenyl group; or

ix) a phenyl group attached simultaneously and ortho to both oxygen atoms except when R⁶ is an ethyl group and when X is an oxygen atom,

and R⁶ is: i) a hydrogen atom;

ii) Cj or higher saturated, optionally mono- or polysubstituted, hnear or branched alkyl;

iv) C3 or higher, optionally mono- or polysubstituted, hnear or branched alkenyl;

v) C3 or higher, optionally mono- or polysubstituted, hnear or branched alkynyl;

vi) a phenyl or optionally mono- or polysubstituted phenyl group; or

and X is: i) an oxygen atom; or

ii) a sulfur atom.

According to a fifth aspect of the invention there is provided a process for the preparation of a compound of the general formula (IV) and its subsequent conversion into a 2-cyanoacrylate polymer:

wherein R⁷ is: i) C4 or higher saturated alkyl or cycloalkyl;

ii) phenyl except when R⁸ is an ethyl group; or

iii) a mono- or polysubstituted phenyl group,

and R⁸ is: i) a hydrogen atom;

vi) a phenyl or optionally mono- or polysubstituted phenyl group; or

and Y is: a negatively charged ion,

which comprises reacting 2-cyanoacrylic acid or an ester thereof with a phosphine in the presence of an inert solvent under polymerisation inhibiting conditions and in the presence of an acidic catalyst under. the conditions hereinabove defined followed by ehmination of the phosphine to give a 2-cyanoacrylate monomer which then polymerises.

Suitable negatively charged ions as values for Y include but are not limited to a chloride or other hahde ion, a trifluoroacetate ion or a perchlorate ion.

Preferably the acidic catalyst has as its counterion the desired negatively charged ion Y of formula (IV).

The following scheme depicts the reaction involved in the process according to the fifth aspect of the invention:

wherein R⁷, R⁸ and Y are as hereinabove defined.

In this fifth aspect of the invention there are provided salts of 2- cyano-3-(trialkylphosphonium)- and 2-cyano-3-(triarylphosphonium) propionic acid and esters thereof which may be employed as precursors to useful polymerisable 2-cyanoacrylic acid esters.

Thus, the invention provides a compound of the general formula (IVa):

wherein R⁷ is: i) C4 or higher saturated alkyl or cycloalkyl;

ii) phenyl except when R⁸ is an ethyl group; or

iii) a mono- or polysubstituted phenyl group,

and R⁸ is: i) a hydrogen atom;

vi) a phenyl or optionally mono- or polysubstituted phenyl group; or

and Y is: a negatively charged ion. Suitable negatively charged ions as values for Y include but are not limited to a chloride or other hahde ion, a trifluoroacetate ion or a perchlorate ion.

In a sixth aspect of the invention the weak nucleophile can be a carbon acid. This provides a further method for the reversible protection of the carbon-carbon double bond of polymerisable 2- cyanoacrylic acid esters.

The process according to the sixth aspect of the invention can be used for the preparation of a compound of the general formula (V) and its subsequent conversion into a 2-cyanoacrylate polymer:

wherein R⁹ is: i) a hydrogen atom;

ii) an electron- withdrawing organic functional group including but not limited to groups such as nitro, carboalkoxy, cyano, acyl, sulfonyl and phosphonyl groups;

and RlO is: an electron- withdrawing organic functional group including but not limited to groups such as nitro, carboalkoxy cyano, acyl, sulfonyl and phosphonyl groups,

and RH is: i) a hydrogen atom;

ii) Ci or higher saturated, optionally mono- or polysubstituted, linear or branched alkyl; iii) C5 or higher saturated, optionally mono- or polysubstituted cycloalkyl or poly (cycloalkyl);

vi) a phenyl or optionally mono- or polysubstituted phenyl group; or

which comprises reacting 2-cyanoacrylic acid or an ester thereof with a singly or doubly activated carbon acid in an inert solvent under polymerisation-inhibiting conditions and in the presence of an acidic catalyst under the conditions hereinabove defined followed by ehmination of the addend to give a 2-cyanoacrylate monomer which then polymerises.

The following scheme depicts the reaction involved in the process according to the sixth aspect of the invention:

wherein R⁹, Rl° and RH are as hereinabove defined.

Thus the invention provides compounds of the general formula (Va):

wherein R⁹ is: i) a hydrogen atom except when R O is a nitro group and RH is an ethyl group;

ii) a carboxymethyl group except when RlO is a nitro group and RH is an ethyl group;

iii) a carboxyethyl group except when RlO is a carboxyethyl group or an acetyl group or a cyano group when RH is an ethyl group;

iv) a carboxyalkyl group wherein the alkyl radical is C³ or higher saturated, linear or branched;

v) an acyl or aroyl group;

vi) any other compatible electron- withdrawing organic functional group including but not limited to nitro, cyano, sulfonyl and phosphonyl groups,

RlO is: any compatible electron-withdrawing organic functional group including but not limited to groups such as nitro, carboalkoxy, cyano, acyl, aroyl, sulfonyl and phosphonyl groups,

and RH is: i) a hydrogen atom;

ii) Ci or higher saturated, optionally mono- or polysubstituted, hnear or branched alkyl; iii) C5 or higher saturated, optionally mono- or polysubstituted cycloalkyl or poly (cycloalkyl);

vi) a phenyl or optionally mono- or polysubstituted phenyl group; or

The processes according to the invention can be carried out in a simple, rapid, facile one-step manner with attendant advantages. Thus, the process according to the invention is a "one-step" process in contrast with the prior art methods described supra with their inherent limitations.

The reversible protection afforded by the invention can be used to protect the carbon-carbon double bond of a wide range of 2- cyanoacrylate monomers including substituted or unsubstituted long- chain alkyl cyanoacrylates and multi-functional cyanoacrylates including bis -cyanoacrylates.

The invention also provides a composition comprising a compound of any of the formulae (I), (II), (III), (IV) or (V) as hereinbefore defined. Such compositions can include excipients such as a thinner.

The compounds of the formulae (I), (II), (HI), (IV) and (V) hereinbefore defined can be used in adhesive compositions. The invention also provides poly(cyanoacrylate) materials formed from a compound of any one of the formulae (I), (II), (III), (IV) and (V) hereinbefore defined.

A further use of the compounds of any one of the formulae (I), (II), (III), (IV) and (V) hereinbefore defined is in the formation of poly (cyanoacrylate) films. Such films include single or multi-layer Langmuir-Blodgett films.

The compounds of the formulae (I), (II), (III), (IV) and (V) hereinbefore defined can also be used in the preparation of poly (cyanoacrylate) nanocapsules. The compounds of the formula (I) are especially suitable for the preparation of such poly(cyanoacrylate) nanocapsules.

Poly(cyanoacrylate) nanocapsules prepared in accordance with the invention suitably contain an active agent such as a drug.

Compounds of any one of the general formulae (I), (II), (El),

(IV) and (V) wherein the esterifying group R², R⁴, R⁶, R⁸ or RH, as appropriate is a terminal alkyne could be precursors to useful 2- cyanoacrylate monomers and polymers which could be further modified by cross-linking via the well-known Glaser oxidative coupling reaction.

Compounds of any one of the general formulae (I), (II), (El), (IV) and (V) wherein the esterifying group R², R⁴, R⁶, R⁸ or RU, as appropriate incorporates di- or poly-yne functionality may be valuable for the formation of thin films having useful non-linear optical properties.

The compounds according to the invention are expected to be capable of broad apphcation, particularly where thin-film technology is involved and especially where Langmuir-Blodgett type films are desirable. Poly(alkyl 2-cyanoacrylate) films are used as semiconductor . coating materials wherein they are applied to act as microlithographic photoresists due to their sensitivity to electron beams and to X-rays as described, for example, in U.S. Patent No. 4,279,984, and in Matveeva, N.K., (1990), Biol. Membr., Vol. 7, No. 11, 1200-1204. Such films are usually deposited by application of a solution of an alkyl 2- cyanoacrylate polymer, or its monomer followed by its subsequent polymerisation. Even solutions of cyanoacrylate polymers tend to be unstable over time as indicated in Patent Publications JP 9262588 and JP 0462558, and vapour-deposition techniques have been devised in an attempt to overcome this disadvantage (Woods, J., Guthrie, J., Rooney, J., Kelly, L., Doyle, A. and Noonan, E., (1989), Polymer, Vol. 30, No. 6, 1091-1098). This requires special apparatus, however.

The compounds according to the invention offer an alternative method of depositing such films since they are stable as solutions in inert solvents and can be converted into poly(alkyl 2-cyanoacrylates) under anionic conditions. Furthermore, when films laid down in this way are Langmuir-Blodgett or other very thin films then the necessary period of exposure to electron beams or to X-rays should be beneficially reduced. Also such thin films can be expected to greatly modify the capacitance effect and the relative permittivity effect thereby improving dynamic memory capability of the microchip. Accordingly, it is expected that these thin films will find apphcation in the manufacture of low power microchips.

Another benefit resulting from the application of thinner films is increased transconductance with accompanying improved efficiency in terms of speed and memory capacity of thus formed devices. Reduced voltages employing such devices result in reduced power dissipation. Additionally, tighter control over threshold voltage means that such devices may find use in lower power applications with sub-threshold operation in VLSI (very large-scale integration) required, for example, in hearing aids and implants. Thinner film thickness also means improved resolution and reduced feature sizes on microchips, such as, for example, the important interconnection feature between two adjacent "gates" resulting in improved overall performance.

When the alkyl ester part of the alkoxycyanopropionic ester molecule contains a metal such as iron (for example, in a ferrocenyl function) and the alkyl of the alkoxy part of the molecule is a long- chain alkyl group, the resulting ordered Langmuir-Blodgett poly(alkyl cyanoacrylate) film laid down on a substrate such as a silicon chip may then be etched with a laser. Such treated areas of film would give rise to low-coke iron or iron oxide indented regions depending on whether the ablation is carried out under an inert atmosphere such as nitrogen or in the oxidising atmosphere of the air, respectively. Also, when sulfur is additionally contained in the alkyl ester radical of such a long- chain alkoxycyanopropionic acid ester, a well-ordered Langmuir- Blodgett poly(alkyl cyanoacrylate) layer would be expected to give semiconductor FeS regions when etched with a laser.

More easily programmable EPROMS may also result from application of this technology.

The prospect of achieving ultra-thin films as described herein opens up a wide range of possible apphcations in the manufacture of future generations of integrated circuits. Many of the key factors which must be present for the specifications of future semiconductor devices as predicted in the literature (see for example Chenming, Hu (1993) Proceedings of the IEEC, Vol. 81, No. 5, p. 682-689), such as, for example, decreased feature size to less than 0.1 μm, improved feature definition, higher speeds, greater density, increased reliability and thinner oxides, are facilitated by the present invention.

Thin, tightly controlled, low impurity films offer many advances in semiconductor device fabrication. Depolymerisation by means of laser (or other high-energy beam) etching has potential apphcations for accurately controlled volumetric geometries. Areas of surface can be selectively insulated. The engineering of regions, interconnects, channels and layers could be accomplished largely through a chemical route using available production equipment. By laying multiple layers of poly(cyanoacrylate) film where the alkyl ester contains a metal, a semiconductor or an oxide (or where the oxide is produced by carrying out ablation in an oxidising atmosphere), laser etching can produce the features hereinabove mentioned. Furthermore, device trimming, essential in analogue integrated circuits, is also more readily achievable to improved accuracies.

The apphcation of the present invention to semiconductor technology may provide digital devices with very low gate delays operating at lower voltages (1.5V), thereby offering greater circuit speeds while maintaining low chip power levels. The reduced feature size, junction depth, and effective channel length could offer SRAM densities up to 4G. While operating voltage can be reduced, as mentioned, the technology could offer tighter control over threshold voltages by ensuring very low impurity levels.

Linear devices could benefit from the improved control in manufacturing and region/feature definition, low power and higher levels of integration. MOS and bipolar technologies are equally amenable to the processes.

Treatment of thin poly(cyanoacrylate) films with laser or high energy plasma gives coke-free clean holes.

Solvent removable (linear poly(cyanoacrylate) films may be laid down on silicon wafers from the monofunctional 2-cyanopropionate derivatives described herein and then masked. Subsequent treatment with laser followed by treatment with hydrofluoric acid (HF) and subsequent removal of remaining polymer using common organic solvents such as benzene, chloroform or acetone would be expected to give clean, well defined holes on the silicon surface. Cross-hnked and insoluble poly(cyanoacrylate) films may also be laid down on a silicon surface from multifunctional 2-cyanopropionate derivatives described herein and again be masked and treated in the manner hereinabove described with laser followed by HF. A further poly(cyanoacrylate) layer could then be deposited on the stable solvent- resistant cross-linked poly(cyanoacrylate) film from an appropriate 2- cyanopropionate derivative. When the ester portion of this derivative contains a metal such as iron, for example, in a ferrocenyl radical, ablation of exposed regions of resulting poly(cyanoacrylate) film in an inert atmosphere would give a layer of metal - in this case iron - on the surface. Such a layer would, of course, be conducting in nature.

A further layer of silicon dioxide could be laid down, where required, by initial deposition of a poly(cyanoacrylate) film from a silicon-containing (ester portion of molecule) 2-cyanopropionate derivative followed by treatment with laser or high energy plasma in an oxygen-rich atmosphere. Such a layer could also be directly laid down on the sihcon surface.

In this way, silicon chips containing insulating, conducting and semiconductor multilayers may be fabricated.

Also phosphorus-containing poly(cyanoacrylate) films could be laid down from equivalent cyanopropionate derivatives directly onto silicon. Ablation of unmasked regions of film with laser in an inert atmosphere should give phosphorus-doped silicon semi-conductor region used in pnp transmission.

Sulfur-containing cyanopropionate derivatives would in the same way as above give sulfur doped semiconductor regions on the silicon surface following treatment of polymer with laser. Such sulfur-doped areas would be expected to improve adhesion of subsequently formed metal films from ablation of metal-containing poly(cyanoacrylate) prepared from a metal-containing (in the ester portion of the molecule) 2-cyanopropionate derivative. Diacetylene functional 2-cyanopropipnate derivatives (ester portion of molecule) would give poly(cyanoacrylate) films which could be further modified. For example, some regions could be exposed to high energy ultra-violet light to give, by a free-radical polymerisation process, semi-conducting poly(acetylene) regions - masked or remaining polymer layer would be an insulating region. Doping of the semi-conducting poly(acetylene) region by, for example, iodine would give conductive zones. Hence three types of region (insulating, semiconducting, conducting) could be designed into the same poly (cyanoacrylate) monolayer. Such techniques would be useful for the fabrication of molecular electronic devices for super-thin pnp transmission with dramatic component size reduction (down to 10-50

A).

A wide variety of poly(cyanoacrylate) films could be prepared from the cyanopropionate derivatives according to the invention for use in photosensitive, non-linear optical and liquid crystal apphcations. Non-linear optical 2-cyanopropionates would possess asymmetric radicals in the alkyl portion of the molecule. In the same way liquid crystal 2-cyanopropionates would possess cholesterol or methoxy/cyanobiphenyl functionality in the alkyl portion of the molecule.

Patent Publication EP 146,505 describes the use of thin (10 μm) poly(alkyl 2-cyanoacrylate) films in a process for image formation. The ability to lay down Langmuir-Blodgett, multi-layer or other very thin films utihsing compounds of the invention which are precursors to alkyl 2-cyanoacrylate esters and thus to poly(alkyl 2-cyanoacrylates) should permit further useful developments in this area.

Conversion of the monomers produced in accordance with the invention into polymer may be carried out by prior application of a base such as an amine or tetraalkylammonium hydroxide to the surface to be coated or application of base from above as vapour, for example once a film of the compound has been laid down on the untreated surface. In addition the compounds prepared in accordance with the invention could be vapour deposited following the method of Woods J., et al. supra. Priming of surfaces to be bonded by a suitable base means that the compounds in accordance with the invention may be used as adhesives as indicated above. The cyanoacrylate monomer produced in situ between the two surfaces would be expected to polymerise rapidly in the presence of base forming a solid polymer and hence an adhesive bond. The presence of an alcohol or phenol co-product may not be disadvantageous since in fact alcohols have been used as physical additives with cyanoacrylate adhesives to impart porous bonding abihty to same as described in Patent Pubhcations JP 55012166 and JP 88039627.

Long chain or fluorine containing alkoxycyanopropionic esters would be expected to wet previously difficult to bond surfaces such as polyolefins or poly(tetrafluoroethylene) (PTFE) and provide adhesive bonds between previously appropriately base-primed substrates.

However, even peeled poly(cyanoacrylate) films have found use in a transfer printing process in Patent Publication JP 8251487. Similarly long chain alkoxcyanopropionic esters instead of aligning themselves onto surfaces as Langmuir-Blodgett films may form micelles in aqueous solution and be used as a means to encapsulate active agents such as drugs upon subsequent polymerisation by addition of a base to the medium to form nanocapsules. This technique of micelle polymerisation has previously been employed starting with alkyl cyanoacrylate monomer to give pilocarpine-containing poly(alkyl cyanoacrylate) nanoparticles (Harmia-Pulkkenes, T, Tuomi, A., and

Kristoffersson, E. in J. Microencapsulation 1989, Vol. 6, No. 1 p. 87). As indicated above, the use of poly(alkyl cyanoacrylates) is not limited to the encapsulation of drugs. Thus poly (alkyl cyanoacrylates) can be used to encapsulate other active agents. They have been used for example in an electrostatic suspension developer (Patent Publication DE-A 35 14 867). Cyanoacrylate monomer itself has been microencapsulated together with colour-former in a heat-developable, photo- and pressure- sensitive composition in Patent Publication JP 92278953. In the same way, alkoxycyanopropionic acid esters should be able to be microencapsulated by poly(alkyl cyanoacrylate) to give an adhesive composition when used in conjunction with appropriate basic primer.

Other potential applications for the compounds prepared in accordance with the invention include use as transparent fixation agents of plant tissues (the portions to be fixed should be treated with appropriate base) which may offer advantages over the more reactive and less 'discriminate' cyanoacrylate monomer described in Patent Publication JP 63255201.

Two recently reported apphcations of poly(alkyl cyanoacrylates) is their use as passivating layers on the hthium anode of hthium-thionyl chloride cells (Hsing Yaw H., Hsien Wen K., J. Power Sources 1989 Vol. 26 No. 3-4 p. 419) and Langmuir-Blodgett poly (cyanoacrylate) films as coatings for indium antimonide capacitors (Matveeva, N.K., Pasekov, V.F., and Sa Vel'eva, L.V. (Mikroelektronika Akad. Nauk. SSSR 1991, Vol 20, No. 5 pp. 501-503)). The compounds prepared in accordance with the invention could be used to lay down such layers in photo-resist fabrication.

Brief Description of Figures

Fig. 1 is a Langmuir isotherm for the Langmuir-Blodgett film formed in Example 7;

Fig. 2 is a Langmuir isotherm for the Langmuir-Blodgett film formed in Example 8;

Fig. 3 is a Langmuir isotherm for the Langmuir-Blodgett film formed in Example 9; and

Fig. 4 is a graph of area at constant pressure versus time before and after transferring a Langmuir-Blodgett film formed as described in Example 9 to a silicon [100] surface. Modes for Carrying Out the Invention

The invention will be further illustrated by the following Examples.

Example 1

Synthesis of 2-cyano-3-hexadecyloxypropionic acid

2-Cyanoacrylic acid (0.98 g), /.-toluenesulfonic acid (0.17 g) and hydroquinone (0.05 g) were dissolved in dry benzene (250 ml) contained in a 500 ml flask which had previously been washed with 10% sulfuric acid and dried using acetone, and which was fitted with a stirrer, a thermometer, sulfur dioxide and argon inlet adaptors, a dosing funnel and a Liebig condenser arranged for distillation. The solution was sparged with sulfur dioxide and 50 ml of water-benzene azeotrope was distilled off in order to ensure anhydrous conditions. The condenser was then arranged for reflux and a solution of n- hexadecyl alcohol (2.42 g) in dry benzene (50 ml) was added dropwise to the boiling contents of the flask with stirring and continuous sparging with dry sulfur dioxide. Following addition of the alcohol, the solution was heated under reflux during two hours. After this time, sparging with sulfur dioxide was substituted by sparging with argon and the volume of the mixture was reduced to 50 ml by distillation of solvent. The residue was extracted using boiling heptane (100 ml), and heptane and remaining benzene were removed in vacuum to give an oil which crystallised. The solid was recrystallised from hexane to give 2- cyano-3-hexadecyloxypropionic acid (1.37 g; 40%), m.p. 63-65°C, calculated for C20H37NO3: C 70.8, H 10.1, N 4.1%; found C 69.15, H 10.07, N 4.65%, *H NMR (CόD₆) 0.81 (3H, t, J = 5.7 Hz, -CH3), 1.18 (28H, m, -CH₂-), 2.87 (1H, ABX dd, Jχ_A = 5.28 Hz, Jχ_B = 4.43 Hz, -CH(CN)Cθ2H), 3.07 (2H, t, J = 6.44 Hz, -OCH₂CH₂-), 3.18 (1H, ABX m, JAB = 9.30 Hz, -OCH₂CH(CN)C0₂H), 3.31 (1H, ABX m, -OCH₂CH(CN)C0₂H) and 7.13 (1H, s, -C0₂H) p.p.m. Example 2

Synthesis of ethyl 2-cyano-3-hexadecyloxypropionate

Ethyl 2-cyanoacrylate (1.25 g), 2-cyanoacrylic acid (0.05 g) and hydroquinone (0.05 g) were dissolved in a mixture of dry benzene (200 ml) and dry toluene (50 ml) contained in a 500 ml flask which had previously been washed with 10% sulfuric acid and then dried using acetone, and which was fitted with a stirrer, a thermometer, sulfur dioxide and argon inlet adaptors, a dosing funnel and a Liebig condenser arranged for distillation. The solution was sparged with sulfur dioxide while water-benzene azeotrope (50 ml) was distilled off in order to ensure anhydrous conditions. The condenser was then arranged for reflux and a solution of n-hexadecyl alcohol (2.7 g) in dry benzene (50 ml) was added to the boiling contents of the flask with stirring and continuous sparging with dry sulfur dioxide. Following addition of the alcohol the mixture was continuously sparged with sulfur dioxide and heated in such a manner that slow distillation of solvent continued during two and one-half hours. After this time, sparging with sulfur dioxide was substituted by sparging with argon and the volume of the reaction mixture was reduced to 50 ml by distillation. The remaining solution was cooled, a solid residue which formed was removed by filtration, and remaining solvent was removed by distillation in vacuum to give a solid product (3.4 g). This was recrystallised from hexane to give ethyl 2-cyano-3-hexadecyloxy propionate (2.37 g; 61%), m.p. 44-46°C, calculated for C22H41NO3: C 71.93, H 11.17, N 3.81%; found C 72.17, H 11.68, N 3.56%, *H NMR (C₆D₆) 0.847 (3H, m, -(CH₂)_nCH₃), 0.913 (3H, t, J = 7.16 Hz, -OCH₂CH3), 1.42 (28H, m, -CH₂-), 3.01 (1H, ABX dd, Jχ_A = 5.21 Hz, Jχ_B = 5.23 Hz, -CH(CN)C0₂Et), 3.23 (2H, t, J = 6.32 Hz, -CH2OCH2CH-), 3.42 (1H, ABX m, JAB = 9.35 Hz, -OCH₂CH(CN) C0₂Et), 3.53 (1H, ABX m, -OCH₂CH(CN)C0₂Et) and 3.88 (2H, q, J = 7.16 Hz, -C0₂CH₂CH₃) p.p.m. Example 3

Synthesis of hexadecyl 2-cyano-3-hexadecyloxypropionate

2-Cyanoacrylic acid (0.96 g, 0.01 mol), -toluenesulfonic acid (0.17 g) and hydroquinone (0.05 g) were dissolved in dry benzene (250 ml) contained in a 500 flask which had previously been washed with 10% sulfuric acid and then dried using acetone, and which was fitted with a stirrer, a thermometer, sulfur dioxide and argon inlet adaptors, a dosing funnel and a Liebig condenser arranged for distillation. The solution was sparged using dry argon while water-benzene azeotrope (50 ml) was distilled off in order to ensure anhydrous conditions. The condenser was then arranged for reflux and a solution of n-hexadecyl alcohol (2.42 g 0.01 mol) in dry benzene (100 ml) was added to the boiling contents of the flask with stirring and continuous sparging with dry sulfur dioxide. Following addition of the alcohol, the mixture was refluxed during two hours. After this time, the sulfur dioxide sparging was substituted by argon sparging and the condenser was arranged for distillation. A solution of n-hexadecyl alcohol (2.6 g, 0.0108 mol) in dry benzene (100 ml) was added dropwise with constant removal of solvent by distillation. Following this addition, dry benzene (200 ml) was added and the mixture was distilled with stirring and constant sparging using argon until the volume had been reduced to 50 ml. The residue was extracted using boiling hexane (100 ml), and hexane and remaining benzene were removed in vacuum after prior coohng and filtration to give a solid residue (3.95 g). This was recrystallised from hexane to give the hexadecyl ester of 2-cyano-3-hexadecyloxypropionic acid (3.4 g; 60%) m.p. 42-43°C, calculated for C36H69NO3: C 76.73, H 10.48, N 2.48%; found C 75.57, H 11.09, N 2.59%, *H NMR (C6D₆) 0.85 (6H, t, J - 6.2 Hz, 2 @ -CH2CH3), 1.12 (4H, m, 2 @ -CH2CH3), 1.33 (52H, m, -CH₂-), 2.94 (1H, ABX dd, Jχ_A = 5.42 Hz, Jχ_B = 5.10 Hz, -CH₂CH(CN)Cθ2-), 3.10 (2H, t, J = 6.3 Hz, -CH OCH₂CH(CN)-), 3.29 (1H, ABX m, J_BA = 9.33 Hz, -OCH₂CH(CN)-), 3.42 (1H, ABX m, -OCH₂CH(CN)-) and 3.86 (2H, t, J = 6.43 Hz, -C0₂CH₂CH₂-) p.p.m. Example 4

Preparation of poly(ethyl 2- cyanoacrylate from ethyl 2-cyano-3- hexadecyloxypropionate

Ethyl 2-cyano-3-hexadecyloxypropionate (0.36 g) was dissolved in ethanol (5 ml) and water (1 ml) and the mixture was stirred during 24 hours to give an amorphous colourless sohd. This sohd was separated by centrifugation and dried in vacuum to give 0.35 g of an equimolar mixture of hexadecyl alcohol and poly(ethyl 2- cyanoacrylate, calculated C 71.93, H 11.17, H 3.81, found C 70.03, H 10.94, N 3.35%. The mixture was washed with alcohol and with acetone, and the sohd residue was dissolved in chloroform. It was then precipitated with hexane, filtered and dried in vacuum to give 0.1 g of poly(ethyl 2-cyanoacrylate), calculated for C6H₇NO₂: C 57.6, H 5.6, N 11.2; found C 58.31, H 6.11, N 10.43%, ^lU NMR (CDCI3) 0.77 (m, - OCH2CH3), 2.20-2.55 (m, -CH₂-) and 4.23 (m, -OCH2CH3) p.p.m.

Example 5

Preparation of polyCethyl 2-cyanoacrylate from triphenyl((2-cyano-2- ethoxycarbonyDethyPphosphonium trifluoroacetate

To a solution of 1.6 g (2 ml, 12.5 mmol) of ethyl 2- cyanoacrylate and 2.6 ml (18 mmol) of trifluoroacetic acid in 2 ml of dry chloroform was added dropwise with stirring and sparging with sulfur dioxide a solution of 3.28 g (12.5 mmol) of triphenylphosphine in 4 ml of dry chloroform. The mixture was stirred at room temperature during 20 minutes and solvents were then evaporated in vacuum. The residual oil contained triphenyl((2-cyano-2- ethoxycarbonyl)ethyl)phosphonium trifluoroacetate, ^{3 l}p NMR 21.82 p.p.m., *H NMR (CDCI3) 1.06 (3H, t, -OCH₂CH₃), 3.72 (IH, m, - CH(CN)C02Et), 4.00 (2H, m, -OCH₂CH₃), and 4.18 and 4.45 (each IH, m, PI13P-CH2-) p.p.m. A solution of 3 g of the above compound in 5 ml of acetone was added dropwise to 30 ml of water and the mixture was stirred during 24 hours to give an amorphous colourless sohd. This sohd was separated by centrifugation, washed sequentially with water, alcohol and acetone, and dried in vacuum. It was then dissolved in chloroform, precipitated using hexane, filtered and dried in vacuum to give 0.72g (96%) of poly(ethyl 2-cyanoacrylate), calculated for C6H7NO2: C 57.6, H 5.6, N 11.2; found C 58.01, H 5.86, N 10.83%, ^XH NMR (CDCI3) 0.77 (3H, -OCH2CH3), 2.20-2.55 (2H, m, -CH₂-) and 4.23 (2H, -OCH2CH3) p.p.m.

Example 6

Preparation of po ethyl 2-cyanoacrylate) from ethyl 2-cyano-4- thiaoctanoate

To a solution of 1.68 g (2 ml, 18.7 mmol) of n-butylmercaptan in 2 ml of dry chloroform was added dropwise with stirring to a solution of 1.6 g (2 ml, 12.5 mmol) of ethyl 2-cyanoacrylate in 2 ml of dry chloroform. The mixture was stirred at 20°C during 24 hours when solvent was evaporated in vacuum to give a colourless transparent oil. This oil was distilled in vacuum to give 1.88 g (70%) of ethyl 2- cyano-4-thiaoctanoate, b.p. 110°C at 0.5 mm Hg, *H NMR (CDCI3) 0.90 (3H, t, J 6 Hz, CH₃CH₂CH₂-), 1.32 (3H, t, J 6.5 Hz, -OCH₂CH₃), 1.4 (2H, m, CH3CH₂CH2-), 2.64 (2H, t, -CH₂CH₂S-), 2.99 and 3.09 (each IH, ABX, -SCH₂CH-), 3.70 (IH, m, -CH₂CH(CN)C0₂Et) and 4.28 (2H, q, J 6.5 Hz, -OCH2CH3) p.p.m. The above compound (1 g) was added dropwise to 30 ml of water and the mixture was stirred during 48 hours to give an amorphous colourless sohd. This sohd was separated by centrifugation, washed with water, dried in vacuum, dissolved in chloroform, precipitated using hexane, filtered and dried in vacuum to give 0.53 g (92%) of poly(ethyl 2-cyanoacrylate), calculated for C6H7NO2: C 57.6, H 5.6, N 11.2; found C 57.23, H. 5.45, N. 11.62%, *H NMR (CDCI3) 0.77 (m, -OCH2CH3), 2.20-2.55 (m, -CH₂-) and 4.23 (m, -OCH₂CH₃) p.p.m. Example 7

Formation of a Langmuir-Blodgett film using 2-cyano-3- hexadecyloxypropionic acid

The title compound was dissolved in pure, dry chloroform to give a solution containing 1 g/L. A measured volume (8 x 10"⁵ L) of this solution was applied to the surface of pure water of pH 7.13 contained in a Langmuir trough fitted with a movable barrier connected to a torsion balance and a data handling system. After allowing time for the chloroform to evaporate, the surface of the trough was swept by the barrier at a speed of 1.2 cm²/s^{_ 1} and the isotherm of surface tension in mN/m versus surface area of the film in cm² was recorded. A classical Langmuir isotherm showing gas, liquid and sohd phases was obtained and is reproduced in Fig. 1.

Example 8

Formation of a Langmuir-Blodgett film using ethyl 2-cyano-3- hexadecyloxypropionate

This experiment was carried out exactly as described for Example 7 supra except that the amount of chloroform solution of the title compound which was apphed to the surface of the water in the trough was 6 x 10^"5 L. The Langmuir isotherm obtained is reproduced in Fig. 2.

Example 9

Formation of a Langmuir-Blodgett film using hexadecyl 2-cyano-3- hexadecyloxypropionate

This experiment was carried out exactly as described for

Example 7 supra. The Langmuir isotherm obtained is reproduced in Fig. 3. Example 10

Formation of a Langmuir-Blodgett film using hexadecyl 2-cyano-3- hexadecyloxypropionate, and its transfer to a silicon IT 001 surface

This experiment was initially carried out in the same way as Example 9 supra. A stable, constant area Langmuir-Blodgett film was obtained and maintained at a surface pressure of 35mN/m. At t = 54s (Fig. 4) a portion of the film was transferred by dipping to a silicon [100] surface of known area, giving a film-transfer ratio of 0.8:1.0. After dipping at t = 84s a stable Langmuir-Blodgett film of reduced constant area was obtained.

Claims

Claims: -

1. A process for the reversible couphng of a weak nucleophile to the carbon-carbon double bond of 2-cyanoacrylic acid or an ester thereof, so as to reversibly protect said bond, which comprises reacting 2-cyanoacrylic acid or an ester thereof with said weak nucleophile in the presence of an inert solvent under polymerisation inhibiting conditions and in the presence of an acidic catalyst.

2. A process according to Claim 1, wherein the weak nucleophile is an alcohol.

3. A process according to Claim 1, wherein the weak nucleophile is a phenol.

4. A process according to Claim 1, wherein the weak nucleophile is a thiol, a thiophenol, a thioamide or a thio or dithio acid.

5. A process according to Claim 1, wherein the weak nucleophile is a dialkyl or diary lphosphite, a dialkyl or diarylthiophosphite, a phosphine, or a phosphorus sulfenyl hahde.

6. A process according to Claim 1, wherein the weak nucleophile is a carbon acid.

7. A process according to any preceding claim, wherein the acidic catalyst is a non-volatile acid.

8. A process according to Claim 7, wherein the non-volatile acid is an ahphatic sulfonic acid or an aromatic sulfonic acid.

9. A process according to Claim 8, wherein the acid catalyst is methanesulfonic acid or /? -toluenesulfonic acid.

10. A process according to any one of Claims 1-6, wherein the acid catalyst is a carboxylic acid.

11. A process according to any one of Claims 1-10, which is carried out under conditions which inhibit anionic polymerisation.

12. A process according to Claim 11, which is carried out in the presence of a weak acid.

13. A process according to Claim 12, wherein the weak acid is sulfur dioxide.

14. A process according to Claim 13, wherein gaseous sulfur dioxide is bubbled into the reaction mixture as a continuous stream.

15. A process according to any one of Claims 1-11, wherein the anionic polymerisation inhibitor is an ahphatic sulfonic acid, an aromatic sulfonic acid or carbon dioxide.

16. A process according to any one of Claims 1-15, which is carried out in the presence of a free radical polymerisation inhibitor.

17. A process according to Claim 16, wherein the free radical polymerisation inhibitor is benzoquinone, hydroquinone, methylhydroquinone or naphthoquinone.

18. A process according to any one of Claims 1-17, wherein the inert solvent is benzene, toluene, xylene, hexane or a chlorinated hydrocarbon.

19. A process according to any one of Claims 1-18, which is carried out at a temperature in the range 20-200°C.

20. A process according to any one of Claims 1-19, wherein the total volume of the reaction solvent is kept constant.

21. A process according to any one of Claims 1-20, wherein when 2-cyanoacrylic acid is used as a starting compound to prepare a 3-alkoxy-2-cyanopropionic acid ester, the water produced is continually removed by azeotropic distillation.

22. A process according to any one of Claims 1-21, wherein when the weak nucleophile is an alcohol or phenol, the alcohol or phenol is added gradually to the reaction mixture.

23. A process according to any one of Claims 1-3 and 7-22 for the preparation of a compound of the general formula (I):

wherein Rl is: i) Cj or higher saturated, optionally mono- or polysubstituted, hnear or branched alkyl;

ii) C5 or higher saturated, optionally mono- or polysubstituted cycloalkyl or poly (cycloalkyl);

iv) C3 or higher, optionally mono- or polysubstituted, hnear or branched alkynyl; or

v) a phenyl or optionally mono- or polysubstituted phenyl group,

and R² is: i) a hydrogen atom;

vi) a phenyl or optionally mono- or polysubstituted phenyl group; or

24. A process according to any one of Claims 1 , 4 and 7-20 for the preparation of a compound of the general formula (II) and its subsequent conversion into a 2-cyanoacrylate polymer:

wherein R³ is: i) Ci or higher saturated, optionally mono- or polysubstituted, hnear or branched alkyl or cycloalkyl;

ii) C3 or higher, optionally mono- or polysubstituted hnear or branched alkenyl or alkynyl; iii) a phenyl or optionally mono- or polysubstituted phenyl group;

iv) a mono- or polysubstituted biphenyl, naphthyl or other cychc or polycyclic aromatic or heteroaromatic group;

v) an acyl or thioacyl group;

vi) a dialkyl- or diarylphosphonyl group; or

vii) a dialkyl- or diarylthiophosphonyl group,

and R⁴ is: i) a hydrogen atom;

v) C3 or higher, optionally mono- or polysubstituted hnear or branched alkynyl;

vi) a phenyl or optionally mono- or polysubstituted phenyl group; or

vii) a mono- or polysubstituted biphenyl, naphthyl or other cychc or polycyclic aromatic or heteroaromatic group,

which comprises reacting 2-cyanoacrylic acid or an ester thereof with a sulfhydryl compound in the presence of an inert solvent under polymerisation inhibiting conditions and in the presence of an acidic catalyst, followed by later ehmination of the sulfhydryl addend to give a 2- cyanoacrylate monomer which then polymerises.

25. A process according to any one of Claims 1, 5 and 7-20 for the preparation of a compound of the general formula (III) and its subsequent conversion into a 2-cyanoacrylate polymer:

wherein R⁵ is: i) Ci or higher linear or branched saturated alkyl;

ii) C5 or higher cycloalkyl; or

iii) a phenyl or optionally mono- or polysubstituted phenyl group,

and R⁶ is: i) a hydrogen atom;

v) C3 or higher, optionally mono- or polysubstituted hnear or branched alkynyl; vi) a phenyl or optionally mono- or polysubstituted phenyl group; or

vii) a mono-or polysubstituted biphenyl, naphthyl or other cychc or polycyclic aromatic or heteroaromatic group,

and X is: i) an oxygen atom; or

ii) a sulfur atom;

which comprises reacting 2-cyanoacrylic acid or an ester thereof with a phosphite or thiophosphite in the presence of an inert solvent under polymerisation inhibiting conditions and in the presence of an acidic catalyst, followed by elimination of the addend to give a 2- cyanoacrylate monomer which then polymerises.

26. A process according to any one of Claims 1, 5 and 7-20 for the preparation of a compound of the general formula (IV) and its subsequent conversion into a 2-cyanoacrylate polymer:

wherein R⁷ is: i) C4 or higher saturated alkyl or cycloalkyl;

ii) phenyl except when R⁸ is an ethyl group; or

iii) a mono- or polysubstituted phenyl group,

and R⁸ is: i) a hydrogen atom;

vi) a phenyl or optionally mono- or polysubstituted phenyl group; or

and Y is: a negatively charged ion,

which comprises reacting 2-cyanoacrylic acid or an ester thereof with a phosphine in the presence of an inert solvent under polymerisation inhibiting conditions and in the presence of an acidic catalyst, followed by elimination of the phosphine to give a 2-cyanoacrylate monomer which then polymerises.

27. A process according to Claim 26, wherein Y is but is not limited to a halide ion, a trifluoroacetate ion or a perchlorate ion.

28. A process according to any one of Claims 1, 6 and 7-20 for the preparation of a compound of the general formula (V) and its subsequent conversion into a 2-cyanoacrylate polymer:

(V)

wherein R⁹ is: i) a hydrogen atom;

ii) an electron-withdrawing organic functional group selected from nitro, carboalkoxy, cyano, acyl, sulfonyl and phosphonyl groups;

and Rl° is: an electron- withdrawing organic functional group selected from nitro, carboalkoxy cyano, acyl, sulfonyl and phosphonyl groups,

and RH is: i) a hydrogen atom;

vi) a phenyl or optionally mono- or polysubstituted phenyl group; or

which comprises reacting 2-cyanoacrylic acid or an ester thereof with a singly or doubly activated carbon acid in an inert solvent under polymerisation-inhibiting conditions and in the presence of an acidic catalyst followed by elimination of the addend to give a 2-cyanoacrylate monomer which then polymerises.

29. A compound of the general formula (Ia):

wherein Rl is: i) a methyl group;

ii) C2 or higher saturated, optionally mono- or polysubstituted, hnear or branched alkyl;

v) C3 or higher, optionally mono- or polysubstituted, hnear or branched alkynyl; or

vi) a phenyl or optionally mono- or polysubstituted phenyl group,

and R² is: i) a hydrogen atom;

ii) Cj, optionally mono- substituted, alkyl;

iii) C₂ saturated alkyl except when Rl is methyl;

iv) C saturated, mono- or polysubstituted alkyl;

v) C3 or higher saturated, optionally mono- or polysubstituted, hnear or branched alkyl; vi) C5 or higher saturated, optionally mono- or polysubstituted cycloalkyl or poly (cycloalkyl);

vii) C3 or higher, optionally mono- or polysubstituted, hnear or branched alkenyl;

viii) C3 or higher, optionally mono- or polysubstituted, hnear or branched alkynyl;

ix) a phenyl or optionally mono- or polysubstituted phenyl group; or

x) a mono- or polysubstituted biphenyl, naphthyl or other cychc or polycyclic aromatic or heteroaromatic group.

30. A compound of the general formula (Ea):

wherein R³ is: i) Ci optionally monosubstituted alkyl wherein the substituent is not a free carboxyl group whenever R⁴ is an ethyl group;

iii) C3 hnear or branched, optionally mono- or polysubstituted saturated alkyl;

5 iv) C₄ hnear or branched, optionally mono- or polysubstituted saturated alkyl wherein the mono- substituent is not a hydrogen atom whenever R⁴ is an ethyl group;

v) C5 or higher linear or branched, optionally mono- 10 or polysubstituted saturated alkyl or cycloalkyl;

15 viii) an unsubstituted phenyl group whenever R⁴ is not an ethyl group;

ix) a mono- or polysubstituted phenyl group;

20 xi) an acyl group other than acetyl except when R⁴ is other than an ethyl group when R³ may then be any acyl group;

xii) a thioacyl group;

xiii) a dialkyl or diaryl phosphonyl group excluding 25 diethyl phosphonyl whenever R⁴ is an ethyl group; xiv) a dialkyl or diaryl thiophosphonyl group excluding diethyl thiophosphonyl when R⁴ is an ethyl group,

and including sulfoxides and sulfones derived from any of i) - x) above,

and R⁴ is: i) a hydrogen atom;

ii) Cj or higher, hnear or branched optionally mono- or polysubstituted saturated alkyl;

iii) C₅ or higher saturated, optionally mono- or polysubstituted cycloalkyl or poly (cycloalkyl);

vi) a phenyl or optionally mono- or polysubstituted phenyl group; or

vii) a mono- or polysubstituted biphenyl, naphthyl or other cychc or polycyclic aromatic or heteroaromatic group.

31. A compound of the general formula (Ela):

wherein R⁵ is: i) a methyl group;

ii) an ethyl group except when R⁶ is an ethyl group or a hydrogen atom;

iii) a propyl group or substituted propyl group;

vi) a cyclohexyl group;

vii) an unsubstituted phenyl group except when R⁶ is an ethyl group or a hydrogen atom and when X is an oxygen atom;

viii) a mono- or polysubstituted phenyl group; or

and R⁶ is: i) a hydrogen atom;

ii) C_\ or higher saturated, optionally mono- or polysubstituted, hnear or branched alkyl;

iv) C3 or higher, optionally mono- or polysubstituted, hnear or branched alkenyl; v) C3 or higher, optionally mono- or polysubstituted, linear or branched alkynyl;

vi) a phenyl or optionally mono- or polysubstituted phenyl group; or

and X is: i) an oxygen atom; or

ii) a sulfur atom.

32. A compound of the general formula (IVa):

wherein R⁷ is: i) C₄ or higher saturated alkyl or cycloalkyl;

ii) phenyl except when R⁸ is an ethyl group; or

iii) a mono- or polysubstituted phenyl group,

and R⁸ is: i) a hydrogen atom;

iii) C5 or higher saturated, optionally mono- or polysubstituted cycloalkyl or poly(cycloalkyl; iv) C3 or higher, optionally mono- or polysubstituted, hnear or branched alkenyl;

vi) a phenyl or optionally mono- or polysubstituted phenyl group; or

and Y is: a negatively charged ion.

33. A compound according to Claim 32, wherein Y is but is not hmited to a hahde ion, a trifluoroacetate ion or a perchlorate ion.

34. A compound of the general formula (Va):

wherein R⁹ is: i) a hydrogen atom except when RlO is a nitro group and RH is an ethyl group;

ii) a carboxymethyl group except when Rl° is a nitro group and RU is an ethyl group;

iii) a carboxyethyl group except when Rl° is a carboxyethyl group or an acetyl group or a cyano group when RU is an ethyl group; iv) a carboxyalkyl group wherein the alkyl radical is C³ or higher saturated, linear or branched;

v) an acyl or aroyl group;

vi) a compatible electron-withdrawing organic functional group selected from nitro, cyano, sulfonyl and phosphonyl groups,

RlO is: a compatible electron-withdrawing organic functional group selected from nitro, carboalkoxy, cyano, acyl, aroyl, sulfonyl and phosphonyl groups,

and RH is: i) a hydrogen atom;

vi) a phenyl or optionally mono- or polysubstituted phenyl group; or

35. A composition comprising a compound of the general formula (I) given and defined in Claim 23.

36. A composition comprising a compound of the general formula (II) given and defined in Claim 24.

37. A composition comprising a compound of the general formula (III) given and defined in Claim 25.

38. A composition comprising a compound of the general formula (IV) given and defined in Claim 26.

39. A composition comprising a compound of the general formula (V) given and defined in Claim 28.

40. A compound of the general formula (I) given and defined in Claim 23, for use in an adhesive composition.

41. A compound of the general formula (E) given and defined in Claim 24, for use in an adhesive composition.

42. A compound of the general formula (IE) given and defined in Claim 25, for use in an adhesive composition.

43. A compound of the general formula (IV) given and defined in Claim 26, for use in an adhesive composition.

44. A compound of the general formula (V) given and defined in Claim 28, for use in an adhesive composition.

45. A poly (cyanoacrylate) material formed from a compound of the general formula (I) given and defined in Claim 23.

46. A poly(cyanoacrylate) material formed from a compound of the general formula (II) given and defined in Claim 24.

47. A poly (cyanoacrylate) material formed from a compound of the general formula (IE) given and defined in Claim 25.

48. A poly(cyanoacrylate) material formed from a compound of the general formula (IV) given and defined in Claim 26.

49. A poly(cyanoacrylate) material formed from a compound of the general formula (V) given and defined in Claim 28.

50. A poly(cyanoacrylate) film formed from a compound of the general formula (I) given and defined in Claim 23.

51. A poly (cyanoacrylate) film formed from a compound of the general formula (II) given and defined in Claim 24.

52. A poly(cyanoacrylate) film formed from a compound of the general formula (III) given and defined in Claim 25.

53. A poly(cyanoacrylate) film formed from a compound of the general formula (IV) given and defined in Claim 26.

54. A poly(cyanoacrylate) film formed from a compound of the general formula (V) given and defined in Claim 28.

55. A poly (cyanoacrylate) film according to any one of Claims

50-54, which is a single or multi-layer Langmuir-Blodgett film.

56. Poly(cyanoacrylate) nanocapsules formed from a compound of the general formula (I) given and defined in Claim 23.

57. Poly (cyanoacrylate) nanocapsules formed from a compound of the general formula (E) given and defined in Claim 24.

58. Poly (cyanoacrylate) nanocapsules formed from a compound of the general formula (IE) given and defined in Claim 25.

59. Poly(cyanoacrylate) nanocapsules formed from a compound of the general formula (IV) given and defined in Claim 26.

60. Poly(cyanoacrylate) nanocapsules formed from a compound of the general formula (V) given and defined in Claim 28.

61. Poly (cyanoacrylate) nanocapsules according to any one of Claims 56-60 containing an active agent.

62. Poly (cyanoacrylate) nanocapsules according to Claim 61, wherein the active agent is a drug.