EP3927762A1

EP3927762A1 - Contact-active antibacterial polymeric materials

Info

Publication number: EP3927762A1
Application number: EP20705218.4A
Authority: EP
Inventors: Helmut Kipphardt; Wolfgang Maison; Serge KLIEWER
Original assignee: Universitaet Hamburg
Current assignee: Metall-Chemie Technologies GmbH; Universitaet Hamburg
Priority date: 2019-02-21
Filing date: 2020-02-21
Publication date: 2021-12-29
Also published as: WO2020169828A1; LU101134B1

Abstract

The invention provides a new polymeric material coated by a cationic polymer, which is active as an anti-bacterial product and has low permeability for non-polar solvents. The coated polymeric material may be obtained by activating the surface of a polymeric carrier material by atmospheric-pressure plasma, treating the activated polymeric carrier material with a concentrated solution of a polymerizable quaternary phosphonium or ammonium salt, and polymerizing the quaternary phosphonium or ammonium salt by action of heat.

Description

Contact-active antibacterial polymeric materials

Background

It is a well-known problem that microorganisms form organized colonies on surfaces embedded in a matrix of extracellular polymeric substances and form sessile populations, known as microbial biofilms (microfouling). In some cases, this microbial biofilm is the conditioning layer for the settlement of larger organisms (macrofouling). Both, microfouling and macrofouling is a major issue for almost any type of material used, e.g., in hospitals, for water purification, water transportation and for textiles as well as in food and pharmaceutical industry. The strategies against biofilm formation include the release of antibiotics or biocides from the corresponding surfaces as well as the co-polymerization of standard polymers, such as polyacrylates, and poly- merizable monomers with biocidal activity; the latter is described, e.g., by C.J. Waschinski et ai. (Adv. Mater. 2008, 20, 104-108). However, the release of antibiotics from the material represents a serious environmental hazard that, e.g. when handling drinking water or foodstuff, can in general not be tolerated, and the co-polymerization with biocidal monomers may result in a polymer with undesired properties containing excessive amounts of critical compounds that are persistent and hard to dispose.

In case of polymeric materials, an alternative and particularly promising approach to prevent biofilm formation is the immobilization of a cationic polymer just on the surface of a carrier material to coat it with an antibacterial layer. With contact-active biocides, such as quaternary ammonium and quaternary phosphonium salts, tethered to the surface, early stages of biofilm formation can be interrupted by ceil lysis of bacteria upon contact to the surface. With such a product, many properties of the carrier material such as stiffness or color are not changed at all or just to a small degree.

Additionally, since the active ingredient is bound covalently to the surface of the carrier, this approach does not release any biocide into the surrounding media, and is thus preventing contamination of the environment and does not contribute to microbial resistance development.

The immobilization of cationic polymers on plastic carrier materials may be realized by a“grafting to” or“grafting from” approach. Both approaches require the activation of the carrier material by a suitable method. The resulting reactive functional groups on the surface of the carrier material may be attached to preformed cationic polymers (grafting to) or allow the assembly of cationic polymers via polymerization of suitable monomers (grafting from). The latter approach is particularly interesting from an economical point of view, because it allows the preparation of contact active plastics with well-established polymerization methods (e.g. radical polymerization) using cheap monomeric building blocks,

According to a publication by J. Thome et al. ( Surf Coat. Tech. 2003, 174-175, 584- 587), the surface of polyethylene (PE) films is treated with low pressure plasma and the plasma-activated material is immersed in solutions of polymerizable quaternary ammonium monomers, which are polymerized at increased temperature. The resulting materials were reported to show water contact angles of about 30-40° suggesting a hydrophilic modification of the initially non-poiar PE surface (water contact angle before functionalization was 105°). Although the high polarity of the surface suggests a successful immobilization of cations on the PE surface, the authors reported a layer thickness of only 1-2.5 nm, which corresponds to a very low density of contact active cations on the material. The use of low pressure plasma is limited to laboratory scale and cannot be scaled up in a straightforward manner to an industrial-scale process. Additionally, the approaches described in the prior art do not yield a truly functioning and durable biocidal product. Layer-thicknesses of only 1-2.5 ran suggest that only a low degree of polymerization of the antibacterial monomers was achieved on the surface of the polymeric carrier material. In view of the small reduction of contact angles and the minimal layer thickness ofbiocidal compounds on the surface of the product, it is clear that with the prior art methods only incomplete layers of antibacterial polymers are achieved. Consequently, the authors have described only relatively weak effects on the colonization of two germs (M lute us and E coli). A true antibacterial effect has not been demonstrated at all. Moreover, the extremely thin layers available from the prior art wear off easily and do not establish a durable product that could provide the desired effect over an extended period of time,

Description of the invention

In the development of an industrially feasible process for the preparation of polymeric materials coated with a highly biocidal and durable layer of a cationic polymer, it was found that the use of atmospher i c-pressure plasma for the activation of the outer surface of the polymeric carrier material in combination with a treatment of the plasma-activated carrier material with a highly concentrated solution of the polymerizable antibacterial monomer yields a sufficiently thick and durable biocidal coating that entirely covers the polymeric carrier. The polymeric materials that are coated by a cationic polymer of the present invention can be prepared quickly and cost-effectively in easily scaled-up, thus, large-scale processes; in particular, due to the use of air plasma, avoidance of vacuum conditions during plasma treatment, and the prevention of toxic or hazardous chemicals or procedures that are needed for common surface activations of polymeric carrier materials, Without releasing any biocides into the environment, the resulting, poly- QAS modified polymers show excellent antibacterial activity against a variety of gram-positive and gram-negative bacteria and provide promising properties for applications; for example, in clinical hygiene management, processing and transportation of drinking and cooling water or packaging and transportation in the food and pharmaceutical industry. Therefore, the present invention provides a polymeric material with strongly bound, homogenous, and robust - thus, stable and durable - surface with excellent antibacterial activity. Thereby, the bulk properties (strength, elasticity, flexibility, color etc.) of the originally employed polymeric carrier material are generally maintained. However, if desired, such properties can also be amended, e.g. by the addition of pigments and crosslinking agents to the solution, by which the antibacterial monomers are applied to the polymeric carrier material. With such additives, the surface of the final product can be further modified; e.g,, hardened or dyed. As carrier for the antibacterial coating, any polymeric material, which can be graft- polymerized (e.g., after plasma-activation) with polymerizable monomers, may be utilized; polyethylene (PE), polypropylene (PP), and Polyurethane (PU) and their derivatives - in particular, with the present invention the coating of PU is made possible and of special interest. In addition to the coated PU carrier materials, polymeric materials in general that are coated with an antibacterial layer in accordance with the present invention can be utilized for a wide range of applications including many examples, where hygiene management is crucial: food packaging, storage or transportation, processing and transportation of water, medical products such as catheters or as stable polymer for joint prostheses or any material surface in a clinical environment. Moreover, the coated polymeric materials can be used for the disinfection of liquids in contact with the surface of the coated materials (e.g., in cooling circuits) and as filter material for the cleavage of polar contaminations and pollutants. The surface of the carrier material (e.g., the PU surface) can be modified by several techniques via chemical activation prior to functionalization with the antimicrobial monomers. Chemical activation of the polymeric carrier material can be achieved with strong acids like sulfuric acid or with oxidants such as potassium chlorate or chromium agents. However, while these wet chemical protocols require rather harsh conditions and often problematic reagents, physical surface activation, like ultraviolet (UV) radiation or plasma (such as atmospheric plasma), does not require toxic reagents and can be integrated into existing production processes for polymeric products (made of, e.g., PE) such as films, foils, or devices. In addition, UV and plasma activation allow rather mild chemical modifications with minimal topological changes, if at all, only in the surface region of devices, maintaining the bulk polymer properties.

Thus, while alternative methods for the modification/activation of the surface of the polymeric carrier material may be used, activation by plasma, in particular of atmospheric-pressure air plasma, is preferred.

For the subsequent functionalization of the surface of the polymeric carrier material, the activated material is treated with a concentrated solution of a polymerizable quaternary phosphonium or ammonium salt. While other polar solvents may be used, aqueous solutions are preferred. The concentration of the polymerizable quaternary phosphonium or ammonium salt needs to be greater than at least 10 w.-%, preferably the concentration is greater than 25 w.-%, more preferably the concentration is greater than 40 w,-% The polymerizable quaternary phosphonium or ammonium salts are quaternized phosphanes and amines comprising at least one substituent that comprises at least one ally!-, styrene-, acrylate-, and/or methacrylate group. Amines as parent compound and, thus , quaternary ammonium salts are preferred. As polymerizable sidechains allyl- and styrene-groups, in particular styrene-groups, are preferred. Preferred polyme- rizable quaternary ammonium salts are [2-(methacryloyloxy)ethyl]tri- methylammonium chloride (METAC) and {vinyIbenzyl)trimethylammonium chloride (VBTAC).

The concentrated solution of a polymerizable quaternary phosphonium or ammonium salt may also comprise additives; e.g. to improve the graft-polymerization with the activated polymeric carrier material or the polymerization of the biocidal monomers with each other or to modify the final appearance (for example the color) of the product Thus, the additives within the concentrated solution of a polymerizable quaternary phosphonium or ammonium salt include crosslinking agents and pigments.

After treatment of the polymeric carrier material with the concentrated solution of a polymerizable quaternary phosphonium or ammonium salt, polymerization is initiated, by, e.g., Plasma, UV-light or heat. Preferably, the polymerization is induced by heating over a period of time, preferably at a temperature of 60-80 °C for 1-2 hours most preferably at a temperature of 70 °C for 1.5 hours.

A preferred method for the preparation of the polymeric material in accordance with the present invention that is coated by a cationic polymer comprises the activation (most preferred by atmospheric-pressure plasma) of the surface of a polymeric carrier material (such as a PE or PP product, most preferred a PE film), treatment of the activated polymeric carrier material with a concentrated solution of a polymerizable quaternary phosphonium or ammonium salt (in particular, of a quaternary ammonium salt that contains an ally!-, styrene-, acrylate-, and/or methacrylate group; preferably of a (vmyibenzyl)tfimethylammonium chloride), and polymerizing the quaternary phosphonium or ammonium salt (preferably by the action of heat; most preferred at a temperature of 70 °C).

THE SURFACE MODIFICATION OF THE PRESENT INVENTION is based on a two-step procedure starting with the activation (e.g., with atmospheric-pressure plasma using air as process gas) of the polymeric carrier (for example, a PE-film), followed by the immobilization of quaternary phosphonium or ammonium salts using radical polymerization protocol that may be heat induced. During plasma-activation, formation of carboxyl, hydroxyl, aldehyde/ketones, and peroxides is initiated through the carbon-hydrogen bond scission of the polymeric backbone. The generated hydrocarbon radicals combine with oxygen or ozone to produce alkoxy/peroxy radicals, which react further to the functional groups mentioned above and serve as initiators for free-radical polymerization of the applied polymerizable quaternary phosphonium and ammonium salts. The general procedure of preparing the layer of a cationic polymer on the surface of a polymeric carrier material is shown in scheme 1. There, the process of the present invention involving a two-step protocol of plasma surface activation and subsequent heat induced radical polymerization is depicted. The resulting cationic surfaces may act as contact biocides via ceil lysis of bacteria on the polymer film (scheme 1). The product that is made available with the present invention is characterized in that the formed biocidal polymer covers the carrier in its entirety, that it provides strong antibacterial activity, and that the biocidal polymer coating is extremely durable and resistant. The surfaces formed by the cationic polymer in accordance with the present invention have a water contact angle of less than 15° corresponding to a high loading of cations on the surface resulting in an extraordinary biocidal and antibacterial activity and a very low permeability for non-polar compounds such as hydrocarbons. Moreover, the thickness of the cationic polymer layer on the surface of the polymeric carrier material is at least 200 nm - preferably, the thickness is greater than 300 nm - , guaranteeing a long acting efficacy.

As demonstrated hereinafter, the polymeric material in accordance with the present invention that is coated by a cationic polymer can be used effectively and safely for anti -bacterial products. In particular, the material is useful in food-applications and medical products, such as work- surfaces, cutting boards, conveyor belts, syringes. catheters, tubings etc. In particular, the polymeric material of the present invention can be used as antibacterial plastic films and wraps for packaging foodstuff and medical devices. The polymeric materials of the present invention can also be used for antifouling applications, for example to prevent macro fouling in tubings for the transportation of cooling water or in closed circuits (e.g., for cooling applications). The products of the present invention can be produced in large scale processes, and while they produce durable anti-bacterial surfaces, overall they comprise only minor amounts of critical compounds and do not leak them into the environment. Thus, the products in accordance with the present invention provide a cost-effective and environmentally friendly solution, when anti- bacter tally or antifouling effective products and surfaces are required.

Moreover, it was surprisingly found that the polymer films modified in accordance with the present invention with a cationic polymer act as efficacious barriers against hydrocarbons. Despite being extremely thin and despite the fact that only extremely small overall amounts of the coating-material have to be used, it was observed that these coatings actively decrease the permeability of the carrier for such non-polar solvents.

In view of the antibacterial potency of the claimed coated polymeric carrier material, they allow to be used for the continuous disinfection of circulating liquids, such as the coolant of a cooling cycle. As observed experimentally, the use of the coated polymeric materials of the present invention stops the growth of microorganisms, prevents the formation of biofilms, and renders the use of biocidal-additives (such as antibiotics or silver salts) completely avoidable. In their application, the coated polymers that are made available with the present invention do not leach any biocidal quartemary ammonium or phosphonlum salt and, thus, provide environmentally and toxicologically unproblematic means for the provision of amicrobial conditions. Assisted by their low permeability for non-polar liquids, such as hydrocarbons, the antiseptic and amicrobial qualities of the coated polymeric carrier material according to present invention render the claimed material very suitable for pipes, hoses, and tubing; in particular, for the storage of water as well as for recirculating systems - e.g,, in cooling applications. Such continuously disinfected stationary or recirculating systems may be used for aqueous or non-aqueous liquids. Finally, it has surprisingly been observed that the highly polar and flexible surfaces of the coated polymeric materials of the present invention attract organic polar compounds that have to be regarded as critical contaminations and pollutants, such as medicaments (e.g., diclofenac), and antibiotics (e.g., amoxicillin), as well as toxic or even valuable inorganic anions (e.g., chromates and uranates). Therefore, coating polymeric carrier materials with large specific surface areas (e.g., sheets, sponge-like structures, and capillary systems) in accordance with the present invention allows for the preparation of filters and absorbers to extract dissolved polar compounds from a liquid phase - in particular, from an aqueous phase. Experimental

A) Instrumental

Atmospheric Air Plasma. For plasma activation, a plasma system from plasmatreat GmbH (Steinhagen, Germany) can be used. The atmospheric-pressure plasma system consists of the generator FG5001 with an applied working frequency of 21 kHz, generating a non-equilibrium discharge in a rotating j et nozzle RD 1004 in combination with the stainless steel tip No 22826 for expanded treatment width of approximately 22 mm. Additionally, the jet nozzle is mounted on a Janome desktop robot type 2300N for repetitious accuracy regarding treatment conditions. The process gas is dry and oil- free air at an input pressure of 5 bar in all experiments.

B) Modification of Polymeric Carrier Materials

Films of the polymeric carrier material (e.g,, PE films) with dimensions of 1x2.5 cm resulting in a surface area of 2.5 cm² were cleaned by dipping (<10 s) into isopropanol with subsequent drying for 20 min at 40 °C. The cleaned films were fixed on a microscope slide and treated with plasma. The jet nozzle velocity was set appropriately (e.g., to 6.6 m/min for PE and to 16.8 m/min for PP) and the gap distance between the plasma jet head and the surface of the polymeric carrier material to be modified was adjusted to 7.0 mm. After plasma treatment, the films were stored in air for 10 min prior to grafting. The concentrated aqueous solution containing the monomer was degassed with nitrogen for 10 min without the film followed by additional 15 min with film inside the vials, which were sealed with a rubber septum for all degassing steps. For the modification reaction, the films enclosed in degassed vials were put in a preheated oil bath (e.g., at 70 °C for 1.5 h polymerization reaction time), cleaned with deionized water in an ultrasonic bath for 3x10 min washing cycles afterwards and finally dried in a stream of nitrogen prior to analysis.

C) Analyses of the obtained coated materials

a) Contact angle measurements. Contact angle data are obtained with an OCA 20 goniometer from dataphysics (Filderstadt, Germany) equipped with three automated dispensing units for different liquid probes, a high-speed video system with CCD-camera, measuring stage and halogen-lighting for static and dynamic contact angle measurements.

b) Long-term stability test. The long-term storage stability was verified via contact angle measurements. The modified polymeric carrier materials were stored at room temperature for one year and every month within this timescale the hydrophilicity of the QAS-layer was investigated. Prior to contact angle measurements the material was washed with 10.0 mL water to clean off dust particles etc. from the surface and dried with nitrogen gas

c) Thickness of the coating layer. Film characterization was carried out by using a ToF-SIMS 5-100 machine of IONTOF company (Munster, Germany). The machine is equipped with a 25 keV Bi primary ion gun, 2 keV O₂ ⁺ and Cs⁺ gun sputter guns, a 30 keV Ga FIB gun and a 20 keV Ar-CIuster gun, which can be either used as analysis or sputter gun. For depth profiling the primary ion gun was operated in high-current bunched mode (/(Bi3⁺) = 0.16 pA), for imaging in low current bunched mode (/(Bi3⁺) - 0.08 pA) with a lateral resolution of about 2 mm. For crater wall imaging of the FIB cuts the burst alignment mode with a lateral resolution of about 300 nm was used (/(Bi3⁺) = 0.15 pA). Depth profiling of the film was done with a 10 keV Arisocf beam with a raster size of 300 x 300 mm² and a current of I Ar1500⁺ = 3.59 nA. Analysis was carried out in the centre of the sputter area by rastering the primary ion gun with 100 x 100 mm ² in noninterlaced mode with a pause time of 2 seconds for charge compensation.

cl) Contact biocidal activity of the QAS-coatings. The Agar-plate diffusion test is based on the DIN-Norm 20645:2005-02 and was used to verify the non-leachable Q AS polymer layer. For diffusion testing of modified carrier materials a two-layer agar-plate was used. The first layer consists of Luria-Bertani agar medium and the top-layer contains the desired bacteria suspended in Luria-Bertani agar medium. The modified polymeric carrier materials are placed on the wet agar medium in contact with the active QAS polymer layer and are incubated over night at optimal bacteria growth condition. After overnight incubation the inhibition zone between the polymeric carrier material and the viable bacteria is measured. Untreated PE material was used as negative control.

e) Surface polarity. The surface polarity of the original and the modified films was measured with deionized water as liquid probe and the Owens-Wendt-Rabel- Kaelble (OWRK)-model for estimation of the surface energy was used. The sessile-drop method and a liquid probe volume of 5 mL per drop were chosen for every contact angle evaluation.

f) Surface charge. For determination of accessible surface charges the fluorescein assay developed by Tiller (J. C. Tiller et ah, Proc Natl Acad Sci USA 2001 , 98, 5981-5985), with slight modifications similar to Murata (H. Murata et al.,

Biomaterials 2007, 28, 4870-4879) was used. Every incubation step was performed in an ultrasonic bath at ambient temperature. Modified polymer films with a total surface area of 1.0 cm² were treated with 10 0 mL of 1 wt% aqueous sodium fluorescein dye solution for 10 min. The films of the polymeric carrier were subsequently rinsed with 100 mL deionized water to remove residual fluorescein. In addition, the films were immersed in water (10.0 mL) three times for each 10 min in an ultrasonic bath. For desorbing the dye, the polymer films were treated with 9.00 mL of 0.1 wt% cetyl trimethyl ammonium chloride (CTAC) solution for 30 min. Subsequently, 10 vol% of PBS -buffer (100 HIM, pH 8,0) were added and the absorbance of the resulting solution at 501 nm was measured. The concentration of desorbed fluorescein was calculated with an extinction coefficient of 77 mM cm ¹. For evaluation of charge and grafting density, sextuple measurements of the modified polymer samples were carried out.

g) Antimicrobial evaluation of the modified polymer films. To examine the antimicrobial activity of the modified films of the present invention, the ASTM

E2149-01 standard test method “ Determining the antimicrobial activity of immobilized antimicrobial agents under dynamic contact conditions” was adopted (with some modifications regarding sample size and bacteria types). The films were charged with 10⁶ CFU/mL of gram- negative (E. coli K12, P. aeruginosa PAOl) and gram-positive (51 aureus ATCC 12600) bacteria. The modified and untreated films were sterilized in 70 %v/v ethanol and dried at room temperature prior to bacteria assays. The films with dimensions of 1x2.5 cm were treated with 2.50 mL diluted bacteria suspension in 15 mL falcon tubes for 1 h under gentle shaking (28 °C for P. aeruginosa, S. epidermidis, S. aureus, 37 °C for E. coli) After treatment time, an aliquot of 50 mL was plated on Luria-Bertani (LB) agar and incubated for 24 h at 28 °C or 37 °C in depending on bacteria strain, The determination of antibacterial activity of the modified films was performed in triplicate.

h) Barrier properties against hydrocarbons. To examine the barrier properties of the modified films against aliphatic hydrocarbons a gravimetric test method was used. For that investigation 10 mL crimp neck vials were filled with approx. 5 g hydrocarbon and enclosed with a circular shaped poly-QAS modified film, After enclosing the mass difference after 24 h was calculated according to the formula;

with:

Dm The mass difference

A Circular area of investigated modified film

t Time intervall

D) Results

As a preferred embodiment of the present invention, a PE film was utilized as polymeric carrier material and vinylbenzyltrimethylammonium chloride (VBTAC) was used as polymerizable quaternary ammonium salt (QAS-monomer). The activation was conducted with atmospheric-pressure air-plasma with a gap distance of 7.0 mm and a treatment speed of 6.6 ml min (for PE,; 16.8 m/min for PP). After treatment with an aqueous VBTAC-solution with a concentration of 40 w.-%, polymerization at a temperature of 70 °C for 1 5 hours was conducted, the material was washed 3-times in an ultrasonic bath with water, and dried in a stream of nitrogen.

As a result, a QAS-coated PE film with a contact angle of 12° and an almost completely wettable surface was obtained (figure 1). The modified PE-films of the present invention were repeatedly washed in water with ultrasonication, followed by contact angle measurement after each cycle to verify the stability of the QAS-polymer on the PE film. As depicted in figure 2, the initial contact angle of 12° was retained after repeated washing cycles of each 10 min in water confirming the presence and durability of highly polar QAS-polymer on the surface. The long term durability of poly-QAS modified PE-films was furthermore investigated by repeated washings over a period of one year (figure 3),

In figure 4 precise depth profiles of VBTAC modified films are shown. As an indicator for the end of the film, the decrease of the Cl signal was chosen. The Ci mass signal remains constant in the substrate. Those precise SIMS depth profiles reveal a thickness of about 300 nm.

The evaluation of the accessible surface charges of modified films via fluorescein assay resulted in a estimated grafting density of 12.6 ± 3.57 pg/cm². This corresponds to a charge density of approximately 3.6 ^. 10¹⁶ N⁺/cm².

The antimicrobial activity of poly-QAS modified polymeric films of the present invention was evaluated by an ASTM method (a standard test for contact active antibacterial films or fabrics) that relies on the incubation of test specimen with microorganisms of defined concentration under dynamic conditions. Aliquots taken from the resulting solution after 1 h, are plated on LB-agar media and incubated again, followed by determination of log reduction values, The modified polymeric materials in accordance with the present invention were challenged by different bacteria with a concentration of 10⁶ CFU / mL. The LB agar plates of incubated bacteria solution after treatment with modified and untreated PE films (50 mL inoculum from solution per plate was used; a) - c); E. coli, P, aeruginosa, S. aureus agar plates obtained after treatment of poly-QAS modified PE films d) - f) E. coli, P. aeruginosa, S. aureus agar plates obtained after treatment of unmodified PE films. Bacterial challenge: 10⁶ CFU/mL) are depicted in figure 5. As easily observable from this assay, a complete reduction of bacteria independent of the bacterial strain is achieved by the poly-QAS modified polymeric films of the present invention. In particular, the antibacterial polymer material coated by a cationic polymer in accordance with the present invention showed excellent activity against gram-negative bacteria like E. coli or P aeruginosa as well as gram-positive bacteria like S. aureus .

An Agar-plate diffusion test based on the DIN-Norm 20645:2005-02 was used to verify the contact biocidal activity of poly-QAS PE. As shown in figure 6, neither a poly-QAS modified PE film (A) nor an unmodified PE film (B) caused a bacteria-free areola around the test specimen confirming that no biocides are released to the medium.

Furthermore, the poly-QAS modified polymeric films of the present invention were evaluated by gravimetric permeation test method for barrier properties against aliphatic hydrocarbons like «-hexane, «-heptane and «-octane (figures 7a and 7b). As easily observable from this assay poly-QAS modified PE films reduced the amount of diffused hydrocarbons for all tested hydrocarbons by half in a timescale of 24 h compared to the original carrier material. For the poly-QAS modified PP films, the barrier properties compared to original PP film are even more enhanced. The amount of diffused «-heptane was reduced by a factor of 3 and for «-hexane by a factor of 7.

The technology of the present invention was also successfully applied to polymeric carrier materials in the form of PP- and PU-films. The preferred PE-, PP-, and PU- films were coated, in particular, with the following polymerizable quaternary phosphonium or ammonium salts:

- [2-(methacryloyloxy)ethyl]trimethylammonium chloride (METAC),

- (viny lbenzy l)trimethy 1 ammonium chloride (VBTAC),

- (vinylbenzyl)tributylphosphonium chloride (Bu-QPS),

- (viny lbenzy l)trimethylpho sphoni um chloride (Me-QPS), and

- diallyldimethylammonium chloride (DADMAC).

The approach, which employed surface-activation via atmospheric-pressure plasma, treatment of the activated polymeric carrier material with a concentrated solution of the polymerizable quaternary phosphonium or ammonium salt, and polymerization of the quaternary phosphonium or ammonium salt by the action of heat, yielded layers of the polymerized quaternary phosphonium or ammonium salt of at least 200 nm and coating loadings of at least 10¹⁵ N⁺/cm² The obtained cationic polymer coated polymeric materials showed highly reduced contact angles (vs. the naked polymeric carrier material) and impressive antimicrobial activities. Moreover, independent of the polymeric carrier material the cationic coatings of the present inventions decreased their permeability for unipolar substances, in particular hydrocarbons.

Claims

1 ) A polymeric material coated by a cationic polymer, obtainable by

• activating the surface of a polymeric carrier material with a surface consisting of polyurethane (PU) by atmospheric-pressure plasma,

• treating the activated polymeric carrier material with a concentrated solution of a polymerizable quaternary phosphonium or ammonium salt, and

• polymerizing the quaternary phosphonium or ammonium salt by action of heat,

to generate a layer of a cationic polymer on the surface of the polymeric carrier material.

2.) The polymeric material according to claim 1, whereby the polymerizable quaternary phosphonium or ammonium salt is a polymerizable quaternary ammonium salt comprising at least one ally!-, styrene-, acrylate-, and/or methacrylate group; preferably the polymerizable quaternary ammonium salt is a (vinylbenzyl)trimethylammonium chloride.

3.) The polymeric material according to claims 1-2, whereby the concentrated solution contains the polymerizable quaternary phosphonium or ammonium salt in a concentration of at least 10 w.-%, preferably at least 25 %, most preferably at least 40 w,-%.

4.) The polymeric material according to claims 1-3, whereby the layer of the cationic polymer on the surface of the polymeric carrier material has a thickness of more than 200 nm, preferably a thickness of more than 300 nm, and/or whereby the layer of the cationic polymer on the surface of the polymeric carrier material shows a water contact angle of less 15°.

5.) The polymeric material according to claims 1 -4, whereby the solution contains also a crosslinking agent and/or a pigment.

6.) Use of a polymeric material coated by a cationic polymer according to claims 1-5 as an anti-bacterial product, in particular as an anti -bacterial plastic film or plastic wrap.

7.) Use of a polymeric material coated by a cationic polymer as a product with low permeability for hydrocarbons.

8.) Use of a polymeric material coated by a cationic polymer for the continuous disinfection of a circulating liquid.

9.) Use of a polymeric material coated by a cationic polymer for the cleavage of organic or inorganic compounds or impurities from a liquid.

10.) The use according to claims 8-9, whereby the liquid is water-based.

11.) The use according to claims 7-10, whereby the polymeric material coated by a cationic polymer is obtainable by

• activating the surface of a polymeric carrier material by atmospheric-pressure plasma,

• polymerizing the quaternary phosphonium or ammonium salt by action of heat.

12.) The use according to claim 1 1, whereby the polymeric carrier material is selected from the list consisting of polyethylene (PE), polypropylene (PP), and polyurethane (PU).

13.) Method for the preparation of a polymeric material coated by a cationic polymer comprising

• activating the surface of a polymeric carrier material with atmospheric- pressure plasma,

• treating the activated polymeric carrier material with a concentrated solution of a polymerizable quaternary phosphonium or ammonium salt, whereby the concentrated solution contains more than 15 w.-% of said quaternary phosphonium or ammonium salt, and

• polymerizing the quaternary phosphonium or ammonium salt by action of heat.