WO2011078675A1

WO2011078675A1 - Security feature

Info

Publication number: WO2011078675A1
Application number: PCT/NL2010/050885
Authority: WO
Inventors: Johannes Krul
Original assignee: Vhp Veiligheidspapierfabriek Ugchelen B.V.
Priority date: 2009-12-24
Filing date: 2010-12-23
Publication date: 2011-06-30
Also published as: EP2516582A1; NL2004018C2

Abstract

The invention relates to the use of a polyisocyano support structure provided with at least one functional group as a security feature, preferably a polyisocyanopeptide support structure, in particular in an article selected from the group comprising security paper, value paper, security documents, identity documents, value documents, vouchers, tickets, labels, prescription forms, certificates and packages. Examples of functional groups comprise luminescent chromophores, compounds having (para)magnetic properties, compounds having an absorption spectrum in the UV range and/or the visible range and/or the IR range or near IR range, compounds showing electrical conductivity, optionally via mutual orientation, biochemical compounds, compounds affording a liquid crystal behaviour to the security feature and combinations thereof.

Description

SECURITY FEATURE

The invention relates inter alia to the use of a certain type of security feature, the security feature itself, an article provided with a security feature and a method of authenticating an article provided with a security feature. The application of a security feature in articles like paper including synthetic "paper" predominantly prepared from plastic, and documents produced therefrom like banknotes and the like is known in the art. For securing this kind of paper and documents produced thereof many securing methods and materials are known in order to prevent easy counterfeiting. The protection, hereinafter named security feature, can be incorporated into the substrate during production. In case of a paper substrate a security paper is obtained. A watermark is the most familiar example of a security feature incorporated during production. Luminescent fibres and security threads in banknotes are generally known to the general public. Also after producing a substrate like paper one or more security features can be added to said substrate , e.g. with the aid of a special printing technique or by applying an optically active element like a hologram or kinegram. In such a situation the nature of the substrate is less significant. In both cases, i.e. during use of either normal paper or security paper as substrate a document comprising one or more security features is obtained.

Security paper is distinguished from paper protected in a different manner because of the fact that a security feature is incorporated in the paper mass during production.

The general public relies on sensory perception in order to recognize the genuineness (authenticating) of an article like a security document or value document, e.g. viewing with the eyes and sensing with the fingers often in order to determine the presence of a security feature and/or its position. In addition to the security threads and watermarks mentioned above security features suited for this purpose comprise inter alia also an optically active structure/print that shows an angularly dependent image/colour like a holographic structure at the front surface of EURO banknotes or an angularly dependent colour at the back thereof. For example, touching by the fingers and/or nails allows sensing a "ridged structure" in the striated rectangular trapezium left above the printed architectonic structure at the front of a EURO banknote.

A subsequent step in detecting a security feature is using simple and cheap aids like an UV lamp, polarisator, conductivity measuring device and the like. This kind of aids is used e.g. during checking the genuineness of a banknote upon payment at a cash deck in a store. These security features that can be detected by means of simple aids are also called second line features. Furthermore, security features are present in banknotes, the existence of which is only known to the competent authorities or persons like commercial banks and/or central banks, and for which specific and sometimes complicated detection equipment is required in order to determine the presence thereof. Then there is talk of third and fourth line features. Finally, there is a fifth level, used by e.g. forensic experts, as has been described in EP 1 902 855 A2.

A transponder is used more and more in order to ensure the genuineness of a document, in particular identity documents. The transponder is incorporated in the document and comprises inter alia data of the legitimate owner. Sometimes the use of a transponder is problematic, e.g. in banknotes. This is caused by the costs and vulnerability in view of the usual way of handling these articles.

Many security features starting from the second level are based on specific properties of chemical compounds. Some examples of patent documents describing certain properties of compounds for use in securing security documents and/or value documents comprise:

luminescence through excitation by electrical current (WO 2004 108426 A2) or by change of shape (WO 01 83237 A1 );

- magnetic behaviour (EP 1 646 057 A2, EP 1 646 056 A1 ); and

- electrical conductivity (US 2006 0075249 A1 ).

In the majority of luminescent features use is made of excitation by light. For the most part the luminescent properties are chosen in the visible or near IR range. Here compounds, materials and configurations are searched, which offer specific final luminescence properties and characteristics as is described for example in DE 10 2006 047 851 A1 , DE 10 2006 047 852 A1 , US 2007 0132984 A1 , US 2007 0187630 A1 and EP 1 801 759 A1

In addition to the paper itself, usually specific fibers, foils, security threads and inks are the direct carriers of the security features. Often in one and the same carrier such as e.g. a security thread, different security features are combined such as materials which show fluorescence and materials that show magnetism. Usually this means that a number of security features are present spatially distributed in/on the carrier. It is also possible to incorporate the security features in inks that are delivered subsequently onto the substrate. If one applies inks having different security features in succession, it is difficult though possible to do so in register, so that multiple, different security features can be detected at one position. It is also possible to incorporate different security features in one and the same ink, thereby simplifying the application in register. Then it is desired that the nature of the compounds comprising the security features, allows forming a stable blend. Using different compounds as security features, of which the dissolution behaviour is less compatible, may interfere with the forming of a stable blend, even including the risk of separation during of after the application. In DE 2005 047 609 A1 it has been tried to solve the problem of application in register of different security features/properties by manufacturing particles having a core-shell structure, wherein the core possesses other properties than the shell.

An object of the invention is to reduce or avoid one or more of the disadvantages of the state of the art mentioned above, and/or to offer a useful alternative.

More particularly, the invention aims at providing a security feature and its use, which feature allows different security features/securing properties to be positioned with respect to one another on molecular scale.

A further object is to provide a compound as security feature having a specific mutual molecular orientation of the active (to be detected) group or groups.

Yet an other object is to establish an efficient and/or specific intramolecular interaction between different active groups or compounds, such as for example between luminescent compounds.

Still another object is to provide a compound wherein functional groups having different properties are combined into one macromolecule.

Still another object is the provision of a security feature that can unite all security levels varying from the first visible level to the machine readable signals for the benefit of the forensic level within a molecule. According to a first aspect of the invention one or more objects are achieved by the use of a security feature according to claim 1 . In the context of the invention the following expressions are used.

A functional group is a compound that is present at the polyisocyano support structure, preferably polyisocyanopeptide support structure, having a visibly perceptible property and/or a measurable property. Properties are exemplified by among others colour, luminescence, (para)magnetism and electric conductivity. Functional groups of a biological kind can also be used such as for example, nucleic acid fragments, proteins, peptides or nucleotides. The expression support structure is used in the context of the present invention to denote a polyisocyano support structure as well as a polyisocyanopeptide support structure.

A reactive group is a group at the polyisocyano support structure or the peptide part or at the functional group, which allows coupling a functional group to the support structure, e.g. a polyisocyano mono and/or dipeptide support structure. Acetylene and azide groups are examples of such reactive groups.

Luminescence is understood to mean emitting electromagnetic radiation after excitation. This expressions comprises both fluorescence and phosphorescence.

Lifetime of the excited state is understood to mean the average lifetime of the excited state. This lifetime is inversely proportional to the rate of decay of the excited state.

The security feature according to the invention comprises a support structure (hereinafter sometimes referred to as the polymer), i.e. a polyisocyano support structure, preferably a chiral polyisocyanopeptide structure, which functions as a carrier for coupling one or more functional groups of the same or different nature and thus having separately visual perceptible or detectable properties or not. Many functional groups can be coupled to one and the same polymer molecule. Because functional groups are present at the chiral carrier in a spatially very specific configuration with respect to one another, very specific and unique intramolecular interactions are possible between the various functional groups that have been coupled and/or the chiral support structure. This results in a response of the security feature to e.g. electromagnetic irradiation that differs significantly from the response of a security feature, wherein the functional group as such, i.e. without the specific intramolecular interactions, is present. It is also possible to couple many different types of functional groups having distinguished functionality to the same support structure, usually the same polymeric support molecule. This allows to give one and the same support structure after functionalizing several properties that can be separately perceived and/or detected like colour, luminescence; (para)magnetic behaviour and e.g. conductivity.

Furthermore, it also belongs to the possibilities to prepare blends of different kinds of functionalized support structures, which have an identical or very similar dissolution behaviour because the molecules possess a corresponding base structure and additionally can be provided with specific groups which effect the dissolution behaviour, thereby reducing the risk of undesired separation during application.

The support structure can be functionalized with only one kind of functional group. Different functional groups can also be present attached to one and the same polymeric molecule, thereby causing the functionalized polymer to show a combination of totally different properties such as for example luminescence and (para)magnetism, a colour and conductivity or different colours in the visible region and absorption in the near infrared range. Also there can be interactions between different kinds of functional groups thereby modifying the behaviour of functional groups with respect to detection with e.g.

electromagnetic radiation. Then a unique signal is to be detected, which cannot be reproduced by blending of the individual functional groups, because in such a case the unique spatial positions and thus the specific intramolecular interactions of the functional groups with respect to one another would be absent. Because the support structure has a helical configuration the skeleton structure will show a CD (circular dichroism) signal, which is detectable by CD spectroscopy, in addition to all signals derived from the functional groups. Furthermore the signal of a functional group can be polarized by the chirality of the skeleton structure like polarized luminescence. In a preferred embodiment the polyisocyano support structure, advantageously the

polyisocyanopeptide support structure, provided with at least one functional group shows circularly polarised luminescence, in particular circularly polarised fluorescence. This characteristic may be derived from the support structure, e.g. the helix configuration, one or more functional groups or combination thereof. This kind of security feature can be detected by an appropiate fluorometer under electromagnetic radiation, e.g. UV illumination, using one or more circularly polarising filters (polarisers). Furthermore it is possible to adjust the solubility of the functionalized polymer by giving at least a part of the side chains of the polymer a character adapted to a desired

environment/solvent through additional groups. In order to establish a useful solubility in an aqueous environment the functionalized polymer is provided also with hydrophilic groups, for example ethylene glycol or cellulose side groups. This allows using the functionalized compounds directly in the (paper) manufacturing process. If the functionalized compound is to be incorporated in a plastic, a more apolar character is required. This can be set by means of apolar side chains and/or additional groups, which are to be attached. From such a plastic a foil can be produced, which then can be used as a socalled foil strip, a patch or a thread in or on the paper. This foil can also be further processed, so that it also attains other properties caused by this specific further processing step. Security fibers having a number of properties can also be manufactured from plastic comprising

functionalized compounds. Then these fibers can be processed e.g. into the paper mass.

The dissolution behaviour adjusted by means of suitable functional groups is also important, when the compounds are to be used in inks or pigments as security features.

A further advantage of the functionalized support structure is that the whole molecule is organic, which is an advantage for application in security inks.

The polyisocyano support structure can be prepared by means of Ni(ll) catalyzed

polymerization starting from an isocyano monomer, like tert-butyl isocyanide. The bulky alkyl groups effect stabilization of the helix thus formed. Functionalized polyisocyanides offering a detectable paramagnetic signal are described, e.g. in Vlietstra, E. J.; Nolte, R. J. M.;

Zwikker, J. W.; Drenth, W.; Meijer, E. W., Synthesis and magnetic properties of a rigid high- spin density polymer with piperidine-N-oxyl pending groups, Macromolecules, 1990, 23, (4), 946-948 and Abdelkader, M.; Drenth, W.; Meijer, E. W., Synthesis and characterization of a stable poly(iminomethylene) with pendant phenoxyl radicals, Chem. Mater. 1991 , 3, (4), 598- 602.

The presence of peptide side chains achieves a more stable helix having a larger rigidity because of the H bridge interactions between the peptide side chains. The preparation of polyisocyanopeptides is described, e.g. in Cornelissen, J. J. L. M.; Graswinckel, W. S.;

Adams, P. J. H. M.; Nachtegaal, G. H.; Kentgens, A. P. M.; Sommerdijk, N. A. J. M.; Nolte, R. J. M. Synthesis and characterization of polyisocyanides derived from alanine and glycine dipeptides. J. Polym. Sci., Part A: Polym. Chem. 2001 , 39, (24), 4255-4264, Cornelissen, J. J. L. M.; Donners, J. J. J. M.; de Gelder, R.; Graswinckel, W. S.; Metselaar, G. A.; Rowan, A. E.; Sommerdijk, N. A.; Nolte, R. J. M. beta -Helical polymers from isocyanopeptides. Science 2001 , 293, (5530), 676-680 en de thesis "Polymerization of Isocyanopeptides" van

Metselaar, G.A., 2006 (ISBN 90-9020135-1 ). In Cornelissen, J. J. L. M. Hierarchical transfer of stereochemical information in synthetic macromolecules, Pure Appl. Chem., 2002, 74, (11), 2021 -2030 diagram 1 shows a large number of synthesized polymers based on isocyanopeptide in view of rather simple amino acids like alanine, glycine, serine and histidine. Examples of reactive groups, in particular an acetylene group or an azide group are described in Schwartz, E.; Kitto, H. J.; de Gelder, R.; Nolte, R. J. M.; Rowan, A. E.;

Cornelissen, J. J. L. M. Synthesis, characterisation and chiroptical properties of 'click'able polyisocyanopeptides. J. Mater. Chem. 2007, 17, (19), 1876-1884, and Schwartz, E.; Koepf, M.; Kitto, H. J.; Espelt, M.; Nebot-Carda, V. J.; De Gelder, R.; Nolte, R. J. M.; Cornelissen, J. J. L. M.; Rowan, A. E. Water soluble azido polyisocyanopeptides as functional-sheet mimics. J. Polym. Sci., Part A: Polym. Chem. 2009, 47, 4150-4164 respectively.

Coupling a functional group via a reactive group to the polyisocyanopeptide support structure is described, e.g. in Rostovtsev, V. V.; Green, L. G.; Fokin, V. V.; Sharpless, K. B. A stepwise Huisgen cycloaddition process: Copper (I) -catalyzed regioselective "ligation" of azides and terminal alkynes. Angew. Chem., Int. Ed. 2002, 41 , (14), 2596-2599.

The functional groups can be selected from the group comprising luminescent

chromophores, compounds having (para)magnetic or electromagnetic properties, compounds having an absorption spectrum in the UV range and/or the visible range and/or the IR or near IR range, compounds showing electrical conductivity (optionally via mutual orientation), biochemical compounds, compounds affording a liquid crystal behaviour to the security feature and combinations thereof. In an embodiment the functional group is a luminescent chromophore. Thiophene, coumarin, perylene and porphyrin can be mentioned as examples. See Kitto, H. J.; Schwartz, E.;

Nijemeisland, M.; Koepf, M.; Cornelissen, J.; Rowan, A. E.; Nolte, R. J. M., Post- modification of helical dipeptido polyisocyanides using the 'click' reaction. J. Mater. Chem. 2008, 18, (46), 5615-5624. In a particular embodiment the chromophore coupled to the support structure exhibits luminescence characteristics through intramolecular interaction of the coupled groups, which characteristics differ from the luminescence characteristics of the same but uncoupled groups. In a further embodiment thereof the emission spectra and/or the lifetime of the exited state of luminescence as a result of the intramolecular interactions between at least one type of functional groups differ from the emission spectra and/or the lifetime of the excited state of the monomeric units of the respective type of functional groups.

According to a particularly preferred embodiment at least two different kinds of luminescent chromophores are coupled to the polyisocyano(peptide) support structure, wherein the emission spectrum of one kind of luminescent chromophore overlaps with the excitation spectrum of the other kind of luminescent chromophore. Examples of such a combination are platinum-porphyrin with perylene, and coumarin and perylene. Kitto et al., supra. In a particular embodiment a paragmagnetic functionality is coupled to the support structure like e.g. a porphyrin , such as is described for a polyisocyanopeptide support structure by Witte, P. A. J.; Castriciano, M.; Cornelissen, J. J. L. M.; Scolaro, L. M.; Nolte, R. J. M.;

Rowan, A. E. Helical polymer-anchored porphyrin nanorods. Chem. Eur. J. 2003, 9, (8), 1775-1781 , comprising a metal ion having unpaired spin, which is incorporated therein. See also Vlietstra, supra and Abdelkader, supra.

In a particular embodiment at least two different functional groups having different electromagnetic properties are bonded to the support structure. Perylene (diimide) is an example of a group for an electrical conductive functionalized polymer. See Schwartz, E.; Palermo, V.; Finlayson, C. E.; Huang, Y.-S.; Otten, M. B. J.;

Liscio, A.; Trapani, S.; Gonzalez-Valls, I.; Brocorens, P.; Cornelissen, J. J. L. M.; Peneva, K.;

Mullen, K.; Spano, F.; Yartsev, A.; Westenhoff, S.; Friend, R. H.; Beljonne, D.; Nolte, R. J.

M.; Samori, P.; Rowan, A. E. 'Helter Skelter-like' Perylene Polyisocyanopeptides. Chem. Eur. J. 2009, 15, 2536-2547.

In a further embodiment of the use according to the invention at least one functional group is a biochemical compound, for example selected from the group of nucleic acid fragments, protein structures, peptides and smaller biochemical compounds like for example the nucleotides thymine and adenine such as described in Otten, M. B. J. PhD thesis:

Functionalized Polyisocyanides. Radboud University, Nijmegen, Netherlands, ISBN: 978-90- 9024890-5. According to yet another embodiment the security feature exhibits the behaviour of a liquid crystal, such as nematic or cholesteric behaviour. See Metselaar, G. A.; Wezenberg, S. J.; Cornelissen, J. J. L. M.; Nolte, R. M.; Rowan, A. E. Lyotropic liquid-crystalline behavior of polyisocyanodipeptides. J. Polym. Sci., Part A: Polym. Chem. 2007, 45, (6), 981 -988.

According to a particular embodiment the security feature has a solubility, which is adapted to the matrix wherein it is incorporated or processed. An example of a group offering hydrophilic behaviour is an alcohol such as ethylene glycol. As described above, apolar functional groups can be used to facilitate incorporating the security feature in a plastic.

Use of the security feature is preferred in articles selected from the group comprising security paper, value paper, security documents, identity documents, value documents, vouchers, tickets, labels, prescription forms, certificates and packages.

According to a subsequent aspect the invention relates to an article, preferably selected from the group comprising security paper, value paper, security documents, identity documents, value documents, vouchers, tickets, labels, prescription forms, certificates and packages, the article comprising at least one security feature comprising a polyisocyano support structure having at least one functional group, preferably a polyisocyanopeptide structure.

According to yet another aspect the invention relates to a security feature comprising a polyisocyano support structure having at least one functional group, preferably a

polyisocyanopeptide structure. If the support structure itself has a characteristic which can be used for securing an article, then the support structure only may also be used as a security feature. E.g. the polyisocyanopeptide showing circularly dichroism due to its helical configuration is a useful security feature. According to yet another aspect the invention also relates to a method of authenticating articles provided with a security feature according to the invention, wherein a property dependent from the functional group and/or from the polyisocyano support is determined, for example via sensory perception, and preferably a machine detectable, more preferably measurable property. Advantageously the method according to the invention uses polarised luminescence spectroscopy to detect circularly polarised luminescence. In a particular embodiment thereof additionally the chirality of a polyisocyano support structure, preferably a polyisocyanopeptide support structure provided with at least one functional group is determined. E.g CD spectroscopy is preferably used to determine circular dichroism.

The preferred embodiments of the use of a security feature according to the first aspect of the invention, which have been described above, are applicable to these aspects of the invention in a similar way.

The invention will be illustrated by means of the attached drawing, wherein:

Fig. 1 is a diagram of a configuration of a polyisocyanopeptide support structure having reactive groups;

Fig. 2 a) - e) are diagrams presenting different possibilities of functionalizing the

polyisocyanopeptide support structure;

Fig. 3 a) - d) are diagrams of a polyisocyanopeptide support structure functionalized with a chromophore and associated spectra; and

Fig. 4 a) - c) are diagrams of a polyisocyanopeptide support structure functionalized with two chromophores and associated spectra.

In Fig. 1 a diagrammatic representation of the structure of a base molecule is shown. It consists of polymerized isocyanide provided with alanine side chains. By means of the side chains of the amino acids beta type H bridge interactions cause a stabilized structure of the helix, of which the helix can be laevorotary or dextrorotary depending on the stereospecific configuration of the amino acid side chains. The base structure exhibits a large stability, wherein the length can vary from about 100 nm to about 20 μηη. These values correspond to a molecular mass of 6.10⁵ to 1 .10^s grmol^"1 (Cornelissen, J.J.L.M.; Donners, J.J.J.M., ; de Gelder, R.; Graswinckel, W.S. ; Metselaar, G.A. ; Rowan, A.E.; Sommerdijk , N.A.J. M.; Nolte, R.J.M., Science 2001 , 293 (5530), 676-680). The terminal amino acid comprises a reactive group indicated by X, with which the functional groups can be attached to the polyisocyano support structure. Another method of preparing a polymer having functional groups is modifying the functional group in such a way that the functionalized polymer is derived therefrom through

polymerization.

Fig. 2 diagrammatically illustrates the flexibility of the polyisocyanopeptide support structure in view of obtaining a functionalized polymer. The functional group itself comprises a reactive group, which is able to react with the reactive group X. In Fig. 2a a schematic example is presented, wherein a polyisocyanopeptide is functionalized with one kind of functional group, indicated here as A.

Fig. 2b provides an example of a polyisocyanopeptide that comprises differing functional groups, indicated here as group A and group B, and that are distributed in blocks.

Fig. 2c provides a diagrammatic example of a polyisocyanopeptide, to which two functional groups, i.e. group A and group B are attached at random. Fig. 2d represents a polyisocyanopeptide having functional groups A and B in an alternating order.

Fig. 2e shows an example of a support molecule functionalized with groups A and B, to which a hydrophilic additional group indicated by a grey circle has been coupled at several positions, thereby allowing the molecule to dissolve in an aqueous environment.

In Fig. 2 only two different kinds of functional groups are shown, but it will be clear that many more different groups may be present. Fig. 3 shows a diagrammatic example of a molecule that comprises one luminescent chromophore as a functional group, i.e. perylene-diimide (A). The occupation level of the functional group is 100 % in this example (see Fig. 2a). De spectral data of this compound and those of the non-coupled units are shown in Figs. 3b - 3d. The black lines indicate the functionalized molecule (the polymer) in this figure; the grey lines the non-coupled units (monomers).

It is immediately evident that the spectral properties of the functionalized polymer differ from those of the assembling monomeric parts. Especially the differences in UV visible absorption (Fig. 3b), in emission (Fig. 3c) and in circular dichroism (CD, Fig. 3d) are striking. In the UV vis region it is clear that the spectrum of the polymer is broadened and shifted to longer wavelengths with respect to the non-coupled units. This is also reflected in the fluorescence- emission spectrum, where the spectrum of the polymer is shifted even tens of nanometers and moreover has a different intensity. A clear signal can be recognized in the perylene chromophore region of the CD spectrum in contrast to the non-coupled units where this signal is absent in this area. The polymer shown in Fig. 3 was prepared as follows. /V-methylmorpholine (NMM) (76 μΙ, 0.69 mmol, 2.5 equiv.) and perylene formamide (200 mg, 0.27 mmol) were dissolved in 50 mL CH₂CI₂ under Schlenk conditions. The resulting solution was cooled to -30°C using acetone/C0₂. Stepwise (3 portions ) a total amount of 180 μΙ_ NMM (1 .64 mmol, 6 equiv) and 39 μΙ diphosgene (0.32 mmol, 1.2 equiv.) were added. TLC was used to watch the reaction progress. First, 2.5 equiv. of NMM were added followed by dropwise addition in 10 minutes of 0.5 equiv. of diphosgene in CH₂CI₂ (3 mL). The temperature was maintained at -30°C during the addition. The same amounts were added a second time. The remaining amounts were needed to complete the reaction. The temperature of the reaction mixture was adjusted to 0°C. Under vigorous stirring the reaction mixture was added to 100 mL of an ice- cold saturated aqueous sodium bicarbonate solution. 100 mL of CHCI₃ was added. The organic layer was separated and washed with an aqueous 10% (w/w) sodium carbonate solution. After in vacuo evaporation of the solvent a red solid was obtained. The solid was purified by column chromatography. The yield was 171 mg (88%) of the isocyanide monomer. The isocyanide monomer (138 mg, 0.194 mmol) was dissolved in CHCI₃. 1/1000 equiv. of nickel (1 mL of a 0.19 mM solution of Ni(CI0₄)₂ in EtOH/CHCI₃) was added to the stirred solution. After 1 h. the isocyanide was consumed completely. The polymer was concentrated to about 10 mL and precipitated in 100 mL of methanol/water (1 :1 v/v) under vigorous stirring. Then the solid was collected by centrifugation and subsequent decantation of the solvent. The solid was again dissolved in chloroform (5 mL) and precipitated in about 60 mL methanol. The solid polymer was again collected. This purifying step was repeated until no monomer emission was observed. Finally the red solid was dried in vacuo. The yield was 135 mg (98%). In Fig. 4 a diagrammatic example shows a molecule that has been functionalized with two different chromophores, i.e. perylene diimide (black, Fig. 4a) (A) and coumarin (grey in Fig. 4a) (B). Fig. 4a diagram representing the functionalized polymer, the occupation of the polymer is 50% A and B respectively and is at random; Fig. 4b comprises the UV visible absorption spectrum and the emission spectrum of the assembling monomeric units. In both the UV visible absorption spectrum and the fluorescence spectrum of the functionalized molecule the presence of both chromophores, i.e. perylene (450-600 nm) and coumarin (300-400 nm) can be seen. Comparing the fluorescence spectrum of the molecule that has been functionalized with both perylene and coumarin (Fig. 4c; grey lines) with the fluorescence spectrum of a molecule that has been functionalized with coumarin only (like diagrammatically shown in Fig. 2a) (Fig. 4c; black line) reveals that in the first case the fluorescence of the coumarin is shifted clearly towards shorter wavelengths and thus there is a specific interaction between these chromophores.

In the abovementioned examples the occupation (degree) of the polymer is mentioned, that is to say that a certain percentage of all terminal amino acids is occupied with a functionality. One can select this percentage as desired upon synthesizing the compounds. A difference in percentage directly effects the intensity of the signal and the degree of the intramolecular interactions.

Claims

1 . Use of a polyisocyano support structure provided with at least one functional group as a security feature.

2. Use according to claim 1 , wherein the polyisocyano support structure is a

polyisocyanopeptide support structure.

3. Use according to claim 1 or 2, wherein the functional group has a sensory perceptible property and/or a physically detectable property.

4. Use according to claim 3, wherein the functional group is selected from the group comprising luminescent chromophores, compounds having (para)magnetic or

electromagnetic properties, compounds having an absorption spectrum in the UV range and/or the visible range and/or the IR range or near IR range, compounds showing electrical conductivity, biochemical compounds, compounds affording a liquid crystal behaviour to the security feature and combinations thereof.

5. Use according to claim 4, wherein the functional group is a luminescent

chromophore, which has luminescence characteristics through intramolecular interaction of the coupled groups, which characteristics differ from the luminescence characteristics of the same but non-coupled groups.

6. Use according to claim 5, wherein the emission spectra and/or the lifetime of the exited state of luminescence as a result of the intramolecular interactions between at least one type of functional groups differ from the emission spectra and/or the lifetime of the excited state of the monomeric units of the respective type of functional groups.

7. Use according to claim 4, wherin the functional group comprises at least two different kinds of luminescent chromophores, wherein the emission spectrum of one kind of luminescent chromophore overlaps with the excitation spectrum of the other kind of luminescent chromophore.

8. Use according to anyone of the preceding claims, wherein the polyisocyano support structure provided with at least one functional group shows circularly polarised

luminescence, in particular circularly polarised fluorescence.

9. Use according to anyone of the preceding claims, wherein a functional group emits in the visible region.

10. Use according to anyone of the preceding claims 1 -8, wherein a functional group 5 emits in the non-visible range.

1 1 . Use according to claim 4, wherein the support structure provided with functional groups shows electrical conductivity through the specific mutual orientation of the functional groups.

10

12. Use according to claim 4, wherein the biochemical compound is selected from the group of nucleic acid fragments, protein structures, peptides and nucleotides.

13. Use according to claim 4, wherein at least two different functional groups having 15 different electromagnetic properties are bonded to the support structure.

14. Use according to anyone of the preceding claims, wherein the security feature shows the behaviour of a liquid crystal.

20 15. Use according to claim 14, wherein the security feature shows a nematic behaviour.

16. Use according to claim 14, wherein the security feature show a cholesteric behaviour.

17. Use according to anyone of the preceding claims, wherein the support structure is 25 provided with an additional group for solubilising the security feature in an aqueous medium.

18. Use according to anyone of the preceding claims 1 -16, wherein the support structure is provided with an additional group for solubilising the security feature in an apolar medium.

30 19. Use according to anyone of the preceding claims, wherein the security feature is incorporated in an ink or pigment.

20. Use according to anyone of the preceding claims in articles selected from the group comprising security paper, value paper, security documents, identity documents, value

35 documents, vouchers, tickets, labels, prescription forms, certificates and packages.

21 . Article selected from the group comprising security paper, value paper, security documents, identity documents, value documents, vouchers, tickets, labels, prescription forms, certificates and packages, the article comprising at least one security feature comprising a polyisocyano support structure having at least one functional group, preferably

5 a polyisocyanopeptide structure.

22. Security feature comprising a polyisocyano support structure having at least one functional group, preferably a polyisocyanopeptide structure.

10 23. Security feature according to claim 22 showing circularly polarised luminescence, in particular circularly polarised fluorescence.

24. Method of authenticating articles provided with a security feature according to claim 21 , wherein a property dependent from the functional group and/or the polyisocyano support

15 structure is determined.

25. Method according to claim 24, wherein the chirality of a polyisocyanopeptide support structure provided with at least one functional group is determined.

20 26. Method according to claim 24 or 25 using polarised luminescence spectroscopy to detect circularly polarised luminescence, in particular circularly polarised fluorescence of the security feature.