Polymers with antimicrobial properties

Abstract

A functionalised polyolefin, a process for preparing the same, and a polyolefin blend comprising the same are provided. The functionalised polyolefin may be used as an antimicrobial polymer additive.

Description

[0001] POLYMERS WITH ANTIMICROBIAL PROPERTIES

[0002] FIELD OF THE INVENTION

[0003] This invention relates to a functionalised polyolefin, a process for preparing the same, and a polyolefin blend comprising the same. The functionalised polyolefin may be used as an antimicrobial polymer additive.

[0004] BACKGROUND TO THE INVENTION

[0005] Antimicrobial resistance and its effects on global health and the associated economic costs are a growing concern. The excessive use of antibiotics as prescription drugs has affected their efficiency and many commonly used small molecule antibiotics have now become ineffective for certain treatments. Furthermore, there is an increasing need for the development of antimicrobial paints and coatings for applications such as food packaging, medical devices and anti-fouling paints, for example for ship hulls. An alternative approach to using small molecule antibiotics or antimicrobial disinfectants is the use of polymeric agents with antimicrobial properties, which will prevent spreading of bacteria in the first place. Antimicrobial polymers possess several advantages such as long-term activity, nonvolatility, chemical stability and minimal residual toxicity. Polymers with antimicrobial activity have become an important field of research and a number of different materials have already entered the market, together with regulatory standards such as ISO 22196. One approach is the incorporation of metal ions such as copper or silver, but these materials tend to have only a limited lifespan as the metal ions will gradually leach out from the polymer material. Biocidal polymers, the type of polymers investigated here, are polymers with intrinsic antimicrobial activity due to the presence of functional groups. Examples of functional groups that have shown antimicrobial properties are quaternary ammonium ions (quats) and related guanidinium, amidinium, imidazolium and phosphonium cations. In addition to ionic interactions, hydrogen bonding is also believed to be important for efficient antimicrobial activity and hence, protonated primary and secondary amines interact more strongly with bacterial cell membranes compared to quaternary ammonium ions, due to the presence of hydrogen bonding interactions.

[0006] The extensive use of small molecule antimicrobial agents including quats, together with their fate after use, has raised some environmental concerns as their disposal could lead to ecological hazards. The use of polymeric quats as polymer additives could provide a solution to this problem through incorporation of the active ingredient into the main polymer, resulting in antimicrobial polymer surfaces after melt blending. F. F. Rossetti, K. Siegmann, J. Koser, I. Wegner, I. Keskin, G. Schlotterbeck and M. Winkler, International Journal of Polymer Science, 2017, 2017, 1-10 describes the use of quats with Cis alkyl chains which were blended together with LDPE through melt compounding. While some of these blended materials showed good antibacterial activity against various bacterial strains such as S. aureus, E. coli and P. aeruginosa, noticeable leaching of the antimicrobial agents was observed, most likely due to poor entanglement of the short alkyl chains with the polymer matrix. Similar observations were made in US20160150778 and EP2824139.

[0007] There is a need for effective antimicrobial polymers that do not exhibit leaching of the antimicrobial agent and have good mechanical and thermal properties.

[0008] SUMMARY OF THE INVENTION

[0009] In a first aspect, provided herein is a functionalised polyolefin of formula PO-X, wherein PO is a polyolefin having a chain length of at least 20 carbon atoms and X is a positively charged functional group or a functional group capable of forming a cation at pH 7.

[0010] In a second aspect, provided herein is a process for preparing the functionalised polyolefin according to the first aspect, the process comprising reacting Zn(PO)2 with iodine to obtain PO-I and reacting PO-I to obtain PO-X, wherein PO has a chain length of at least 20 carbon atoms.

[0011] In a third aspect, provided herein is a polyolefin blend comprising a first polyolefin and a second polyolefin, wherein the first polyolefin is a functionalised polyolefin according to the first aspect.

[0012] In a fourth aspect, provided herein is a process for preparing the polyolefin blend according to the third aspect, the process comprising melt blending the first polyolefin with the second polyolefin.

[0013] In a fifth aspect, provided herein is use of a functionalised polyolefin according to the first aspect as an antimicrobial polymer additive.

[0014] In a sixth aspect, provided herein is a method for imparting antimicrobial properties to a surface, the method comprising applying a functionalised polyolefin according to the first aspect or a polyolefin blend according to the third aspect to the surface.

[0015] In a seventh aspect, provided herein is a surface or article comprising (i) a functionalised polyolefin according to the first aspect or (ii) a polyolefin blend according to the second aspect.

[0016] BRIEF DESCRIPTION OF FIGURES

[0017] Figure 1 shows fold change viable bacteria compared to LDPE control. ** shows the statistical significance with P-value < 0.001.

[0018] Figure 2 shows the weight fraction of the active antimicrobial compounds in the PE additive. DETAILED DESCRIPTION

[0019] The commercial availability of alkyl chains in the form of alkyl halides, generally derived from naturally occurring fatty acids, is limited to chain lengths up to Cis. Given the low entanglement molecular weight of polyethylene (Te-1200 Da), longer alkyl chains should ensure permanent entanglement of the antimicrobial agent within the PE matrix during melt blending and thereby minimize the risk of leaching of the active antimicrobial agent into the environment. Methods described herein enable the synthesis of various chain lengths, such as an average of Cis, C30, Ces, and Ciso. As described in R. von Goetze, A. Aljaber, K.-Y. Lee, G. Hill, C. Wallis and G. J. P. Britovsek, Polymer Chemistry, 2022, 13, 6377-6385 (incorporated herein by reference), such longer alkyl halides are easily prepared via an catalysed chain growth reaction (CCG) starting from diethyl zinc and ethylene to generate ZnPE2.

[0020] After quenching, for example with iodine, this unique CCG method based on an iron bis(imino)pyridine catalyst and diethyl zinc, generates 1-iodo alkanes with high selectivity as a Poisson distribution of any desired chain length.

[0021] Described herein is a functionalised polyolefin of formula PO-X, wherein PO is a polyolefin having a chain length of at least 20 carbon atoms. X may be a positively charged functional group. X may be a functional group capable of forming a cation at pH 7. X may be an antimicrobially active polar moiety. Functionalised polyolefins as described herein may be used as antimicrobial polymer additives and in methods for imparting antimicrobial properties to a surface.

[0022] Antimicrobially active groups

[0023] X is an antimicrobially active group and can interact with and disrupt negatively charged cell membranes. Due to its polarity, X repels the non-polar polymer matrix (e.g. the second polyolefin in polymer blends as described herein) and diffuses to the surface, thereby providing antimicrobial activity at the surface of the polymer.

[0024] As described herein, X is present at the end of a polyolefin chain. Accordingly, “PO-X” means that X is present at the end of a polyolefin (PO) chain. PO-X can be described as an end-functionalised polyolefin.

[0025] X may be a cation or capable of forming a cation at pH 7, wherein the cation is selected from an ammonium cation, a phosphonium cation, a pyridinium cation, an imidazolium cation, an amidinium cation, and a guanidinium cation. An ammonium cation may be represented by the formula: wherein each R1is independently selected from H and an organic moiety, such as alkyl (e.g. C1-C10 alkyl (e.g. C3-C10 cycloalkyl), Ci-Ce alkyl or C1-C2 alkyl), alkenyl (e.g. C2-C10 alkenyl, C2-C6 alkenyl or C2-C3 alkenyl), alkynyl (e.g. C2-C10 alky ny I, C2-C6 alkynyl or C2-C3 alkynyl), aryl (e.g. Ce-C-io aryl) or heteroaryl (e.g. C5-C10 heteroaryl). It will be appreciated that each of the organic moieties may be optionally substituted e.g. by halo, amino, thiol, alkoxy (e.g. Ci-Ce alkoxy or C1-C2 alkoxy), -OH group, or a combination thereof. In some embodiments, the ammonium cation is a quaternary ammonium cation, i.e. each R1is other than H.

[0026] A phosphonium cation may be represented by the formula: wherein each R2is independently selected from H and an organic moiety, such as alkyl (e.g. C1-C10 alkyl (e.g. C3-C10 cycloalkyl), Ci-Ce alkyl or C1-C2 alkyl), alkenyl (e.g. C2-C10 alkenyl, C2-C6 alkenyl or C2-C3 alkenyl), alkynyl (e.g. C2-C10 alkynyl, C2-C6 alkynyl or C2-C3 alkynyl), aryl (e.g. Ce-C-io aryl) or heteroaryl (e.g. C5-C10 heteroaryl). It will be appreciated that each of the organic moieties may be optionally substituted e.g. by halo, amino, thiol, alkoxy (e.g. Ci-Ce alkoxy or C1-C2 alkoxy), -OH group, or a combination thereof. In some embodiments, the phosphonium cation is a quaternary phosphonium cation, i.e. each R2is other than H.

[0027] A pyridinium cation may be represented by the formula: wherein each R3, if present, may independently be selected from halo, amino, thiol, -OH group, alkyl (e.g. C1-C10 alkyl (e.g. C3-C10 cycloalkyl), Ci-Ce alkyl or C1-C2 alkyl), alkenyl (e.g. C2-C10 alkenyl, C2-C6 alkenyl or C2-C3 alkenyl), alkynyl (e.g. C2-C10 alkynyl, C2-C6 alkynyl or C2-C3 alkynyl), aryl (e.g. Ce-C-io aryl), heteroaryl (e.g. C5-C10 heteroaryl), alkoxy (e.g. Ci-Ce alkoxy or C1-C2 alkoxy), or a combination thereof. It will be appreciated that each of the organic moieties (e.g. alkyl, alkenyl, alkynyl, aryl, heteroaryl and alkoxy) may be optionally substituted e.g. by halo, amino, thiol, alkoxy (e.g. Ci-Ce alkoxy or C1-C2 alkoxy), -OH group, or a combination thereof. In some embodiments, the pyridinium cation is pyridinium (i.e. no R3is present). An imidazolium cation may be represented by the formula: wherein R4may be selected from H and an organic moiety, such as alkyl (e.g. C1-C10 alkyl (e.g. C3-C10 cycloalkyl) or Ci-Ce alkyl), alkenyl (e.g. C2-C10 alkenyl), alkynyl (e.g. C2-C10 alkynyl), aryl (e.g. Ce-C-io aryl) or heteroaryl (e.g. C5-C10 heteroaryl), and R5may be selected from H, halo, amino, thiol, -OH group, alkyl (e.g. C1-C10 alkyl (e.g. C3-C10 cycloalkyl), Ci-Ce alkyl or C1-C2 alkyl), alkenyl (e.g. C2-C10 alkenyl, C2-C6 alkenyl or C2-C3 alkenyl), alkynyl (e.g. C2-C10 alkynyl, C2-C6 alkynyl or C2-C3 alkynyl), aryl (e.g. Ce-C-io aryl), heteroaryl (e.g. C5-C10 heteroaryl), alkoxy (e.g. Ci-Ce alkoxy or C1-C2 alkoxy), or a combination thereof. It will be appreciated that each of the organic moieties may be optionally substituted e.g. by halo, amino, thiol, alkoxy (e.g. Ci-Ce alkoxy or C1-C2 alkoxy), -OH group, or a combination thereof. In some embodiments, the imidazolium cation is imidazolium (i.e. R4and R5are both H).

[0028] An amidinium cation may be represented by the formula: wherein each R6is independently selected from H and an organic moiety, such as alkyl (e.g. C1-C10 alkyl (e.g. C3-C10 cycloalkyl), Ci-Ce alkyl or C1-C2 alkyl), alkenyl (e.g. C2-C10 alkenyl, C2-C6 alkenyl or C2-C3 alkenyl), alkynyl (e.g. C2-C10 alkynyl, C2-C6 alkynyl or C2-C3 alkynyl), aryl (e.g. Ce-C-io aryl) or heteroaryl (e.g. C5-C10 heteroaryl). It will be appreciated that each of the organic moieties may be optionally substituted e.g. by halo, amino, thiol, alkoxy (e.g. Ci-Ce alkoxy or C1-C2 alkoxy), -OH group, or a combination thereof.

[0029] A guanidinium cation may be represented by the formula: wherein each R7is independently selected from H and an organic moiety, such as alkyl (e.g. C1-C10 alkyl (e.g. C3-C10 cycloalkyl), Ci-Ce alkyl or C1-C2 alkyl), alkenyl (e.g. C2-C10 alkenyl, C2-C6 alkenyl or C2-C3 alkenyl), alkynyl (e.g. C2-C10 alkynyl, C2-C6 alkynyl or C2-C3 alkynyl), aryl (e.g. Ce-C-io aryl) or heteroaryl (e.g. C5-C10 heteroaryl). It will be appreciated that each of the organic moieties may be optionally substituted e.g. by halo, amino, thiol, alkoxy (e.g. Ci-Ce alkoxy or C1-C2 alkoxy), -OH group, or a combination thereof. Chain length

[0030] As used herein, “chain” refers to the main chain (backbone) of a polymer, e.g. polyolefin. Accordingly, “chain length” refers to the number of atoms (e.g. carbon atoms) in the chain. For example, in the following example where PO is PE and n is 31 , the chain length is 66 carbon atoms:

[0031] 3

[0032] To ensure permanent entanglement of the functionalised polyolefin (PO-X) within another polyolefin (such as the second polyolefin in polymer blends as described herein), the chain length of PO-X should preferably be larger than the entanglement molecular weight of the other polyolefin. For linear polyethylene (PE), the entanglement molecular weight is approximately 1000-1200 g / mol (C / o-Cao), but this will be shorter for branched PE. As described herein, PO has a chain length of at least 20 carbon atoms. As the chain length increases, functionalisation of a given chain becomes more difficult because chain length influences solubility. In some embodiments, the PO chain of PO-X contains 20 to 100 carbon atoms, 24 to 96 carbon atoms, 26 to 92 carbon atoms, 30 to 90 carbon atoms, 34 to 88 carbon atoms, 38 to 86 carbon atoms, 42 to 84 carbon atoms, 46 to 82 carbon atoms, 50 to 80 carbon atoms, 54 to 76 carbon atoms, or 60 to 70 carbon atoms. In some embodiments, the PO chain of PO- X contains 20 to 100 carbon atoms, 24 to 96 carbon atoms, 26 to 92 carbon atoms, 30 to 90 carbon atoms, 34 to 88 carbon atoms, 38 to 86 carbon atoms, 42 to 84 carbon atoms, 46 to 82 carbon atoms, 50 to 80 carbon atoms, 54 to 76 carbon atoms, or 60 to 70 carbon atoms on average. In some embodiments, the PO chain of PO-X contains 50 to 80 carbon atoms on average.

[0033] The average number of carbon atoms in a chain may be determined by methods known to the skilled person, such as13C-NMR analysis or GO analysis. Methods described herein result in a Poisson distribution of linear alkanes. This allows quantitative13C NMR analysis to be used to estimate the mean chain length Cnby comparing integrals for CH3 with those for CH2 signals. Further analysis can be achieved by GC-FID. The average molecular weight is generally too low for accurate GPC analysis, whereas analysis by GC-FID will only capture part of the total distribution, because the longer alkanes are only partially soluble and insufficiently volatile for GC analysis. Only the first part of the total distribution is therefore quantifiable, and these values can be used as inputs for the Poisson equation to extract A, the mean number of inserted ethylene units ( / _ is the amount of catalyst used). The total amount of each alkane of chain length n obtained at the end of the reaction can then be calculated:

[0034] Poisson equation : mol Comparison of the average chain lengths determined by GC and NMR analysis shows excellent agreement.

[0035] Accordingly, when reference is made herein to an “average” chain length, this refers to the mean chain length Cnas determined by13C NMR analysis. Alternatively, this may refer to the mean chain length as determined by GC (such as GC-FID).

[0036] There appears to be no convenient nomenclature to describe mixtures of compounds with long alkyl chains, where the length of the chains follows a Poisson distribution, other than quoting an Mnvalue. In order to describe the chain length in the product mixtures, the italicised n value (n) is used herein to describe an average chain length, i.e. CnH2n±2to describe a mixture of alkanes with an average chain length n. The same nomenclature is used for other related compounds, i.e. Zn(C3oHei)2 will result in C30H62 upon hydrolysis, or C30H61I upon reaction with iodine.

[0037] Polymer blends

[0038] Described herein is a polyolefin blend comprising a first polyolefin and a second polyolefin, wherein the first polyolefin is a functionalised polyolefin as described herein. It will be appreciated that the second polyolefin is distinct in structure from the first polyolefin.

[0039] The first polyolefin and the second polyolefin may both comprise the same repeating units. For example, the first polyolefin may be a functionalised polyethylene and the second polyolefin may be polyethylene. Alternatively, the first polyolefin and the second polyolefin may each comprise different repeating units. For example, the first polyolefin may be a functionalised polyethylene and the second polyolefin may be polypropylene.

[0040] When reference is made to the loading of a component, this is relative to the total mass. For example, for a polymer blend in which PE-X (wherein X is the antimicrobial agent) is present at a loading of 2 wt%, 10 g of the polymer blend contains 0.2 g of PE-X.

[0041] When incorporated in a polymer blend, even very low loadings of functionalised polyolefins provide antimicrobial properties. In a polymer blend as described herein, the first (functionalised) polyolefin may be provided at a loading of at least 0.01 wt%, at least 0.05 wt%, at least 0.1 wt%, at least 0.5 wt%, at least 0.75 wt%, at least 1 wt%, at least 1 .25 wt%, at least 1 .5 wt%, at least 1 .75 wt%, or at least 2 wt% relative to the total mass of the polyolefin blend. The first (functionalised) polyolefin may be provided at a loading of at most 4 wt%, at most 3.5 wt%, at most 3 wt%, at most 2.5 wt%, at most 2 wt%, at most 1 .75 wt%, at most 1 .5 wt%, at most 1 .25 wt%, at most 1 wt%, at most 0.75 wt%, or at most 0.5 wt% relative to the total mass of the polyolefin blend. For example, the first (functionalised) polyolefin may be provided at a loading of 0.01 wt% to 4 wt%, 0.05 wt% to 3 wt%, 0.1 wt% to 2.5 wt%, 0.5 wt% to 2 wt%, or 1 wt% to 2 wt% relative to the total mass of the polyolefin blend. In some embodiments, the first (functionalised) polyolefin may be provided at a loading of about 2 wt% relative to the total mass of the polyolefin blend.

[0042] Processes for preparing functionalised polyolefins and polyolefin blends

[0043] Functionalised polyolefins as described herein may be prepared, for example, by a process comprising reacting Zn(PO)2 with iodine to obtain PO-I and reacting PO-I to obtain PO-X, wherein PO has a chain length of at least 20 carbon atoms. Zn(PO)2 may be produced by polymerising an olefin in the presence of a zinc alkyl and a catalyst system. The steps for reacting PO-I to obtain PO-X will depend on the identity of X. For example, this step may comprise reacting PO-I with a tertiary amine, with a pyridine, or with a tertiary phosphine. In some embodiments, PO-I may be converted to PO- NH2, followed by a reaction with a cyanoguanidine.

[0044] As described herein, the functionalised polyolefins may be incorporated into polyolefin blends. Polyolefin blends as described herein may be prepared, for example, by melt blending the functionalised polyolefin with a second polyolefin.

[0045] Aspects and embodiments of a functionalised polyolefin, a process for preparing the functionalised polyolefin, a polyolefin blend, a process for preparing a polyolefin blend, uses of a functionalised polyolefin, methods for imparting antimicrobial properties to a surface, and a surface or article comprising a functionalised polyolefin or a polyolefin, as described herein, are set out in the following clauses.

[0046] 1 . A functionalised polyolefin of formula PO-X, wherein:

[0047] PO is a polyolefin having a chain length of at least 20 carbon atoms; and

[0048] X is a positively charged functional group or a functional group capable of forming a cation at pH 7.

[0049] 2. The functionalised polyolefin of clause 1 , wherein PO is polyethylene (PE) or polypropylene (PP).

[0050] 3. The functionalised polyolefin of clause 2, wherein PO is polyethylene (PE).

[0051] 4. The functionalised polyolefin of any preceding clause, wherein X is a positively charged functional group.

[0052] 5. The functionalised polyolefin of any preceding clause, wherein X is selected from an ammonium cation, a phosphonium cation, a pyridinium cation, an imidazolium cation, an amidinium cation, and a guanidinium cation.

[0053] 6. The functionalised polyolefin of any preceding clause, wherein X is selected from an ammonium cation, a phosphonium cation, a pyridinium cation, and a guanidinium cation. 7. The functionalised polyolefin of any preceding clause, wherein X is selected from an ammonium cation, a pyridinium cation, and a guanidinium cation.

[0054] 8. The functionalised polyolefin of any preceding clause, wherein X is an ammonium cation.

[0055] 9. The functionalised polyolefin of clause 8, wherein the ammonium cation is a quaternary ammonium cation.

[0056] 10. The functionalised polyolefin of any preceding clause, wherein X is a pyridinium cation.

[0057] 11 . The functionalised polyolefin of any preceding clause, wherein X is a guanidinium cation.

[0058] 12. The functionalised polyolefin of any preceding clause, wherein X is a phosphonium cation.

[0059] 13. The functionalised polyolefin of clause 12, wherein the phosphonium cation is a quaternary phosphonium cation.

[0060] 14. The functionalised polyolefin of any preceding clause, wherein X is a functional group capable of forming a cation at pH 7.

[0061] 15. The functionalised polyolefin of any preceding clause, wherein the cation is selected from an ammonium cation, a phosphonium cation, a pyridinium cation, an imidazolium cation, an amidinium cation, and a guanidinium cation.

[0062] 16. The functionalised polyolefin of any preceding clause, wherein the cation is selected from an ammonium cation, a phosphonium cation, a pyridinium cation, and a guanidinium cation.

[0063] 17. The functionalised polyolefin of any preceding clause, wherein the cation is selected from an ammonium cation, a pyridinium cation, and a guanidinium cation.

[0064] 18. The functionalised polyolefin of any preceding clause, wherein the cation is an ammonium cation.

[0065] 19. The functionalised polyolefin of clause 18, wherein the ammonium cation is a quaternary ammonium cation.

[0066] 20. The functionalised polyolefin of any preceding clause, wherein the cation is a pyridinium cation. 21 . The functionalised polyolefin of any preceding clause, wherein the cation is a guanidinium cation.

[0067] 22. The functionalised polyolefin of any preceding clause, wherein X is selected from:

[0068] 23. The functionalised polyolefin of any preceding clause, wherein the cation is a phosphonium cation.

[0069] 24. The functionalised polyolefin of clause 23, wherein the phosphonium cation is a quaternary phosphonium cation.

[0070] 25. The functionalised polyolefin of any preceding clause, wherein X is selected from triphenylphosphonium and tributylphosphonium.

[0071] 26. The functionalised polyolefin of any preceding clause, wherein the chain length of PO follows a Poisson distribution.

[0072] 27. The functionalised polyolefin of any preceding clause, wherein PO has a chain length of 20 to 200 carbon atoms.

[0073] 28. The functionalised polyolefin of any preceding clause, wherein PO has a chain length of 20 to 180 carbon atoms.

[0074] 29. The functionalised polyolefin of any preceding clause, wherein PO has a chain length of 20 to 100 carbon atoms.

[0075] 30. The functionalised polyolefin of any preceding clause, wherein PO has a chain length of 24 to 96 carbon atoms.

[0076] 31 . The functionalised polyolefin of any preceding clause, wherein PO has a chain length of 26 to 92 carbon atoms.

[0077] 32. The functionalised polyolefin of any preceding clause, wherein PO has a chain length of 30 to 90 carbon atoms. 33. The functionalised polyolefin of any preceding clause, wherein PO has a chain length of 34 to 88 carbon atoms.

[0078] 34. The functionalised polyolefin of any preceding clause, wherein PO has a chain length of 38 to 86 carbon atoms.

[0079] 35. The functionalised polyolefin of any preceding clause, wherein PO has a chain length of 42 to 84 carbon atoms.

[0080] 36. The functionalised polyolefin of any preceding clause, wherein PO has a chain length of 46 to 82 carbon atoms.

[0081] 37. The functionalised polyolefin of any preceding clause, wherein PO has a chain length of 50 to 80 carbon atoms.

[0082] 38. The functionalised polyolefin of any preceding clause, wherein PO has a chain length of 54 to 76 carbon atoms.

[0083] 39. The functionalised polyolefin of any preceding clause, wherein PO has a chain length of 60 to 70 carbon atoms.

[0084] 40. The functionalised polyolefin of any preceding clause, wherein PO has a chain length of 20 to 200 carbon atoms on average.

[0085] 41 . The functionalised polyolefin of any preceding clause, wherein PO has a chain length of 20 to 180 carbon atoms on average.

[0086] 42. The functionalised polyolefin of any preceding clause, wherein PO has a chain length of 20 to 100 carbon atoms on average.

[0087] 43. The functionalised polyolefin of any preceding clause, wherein PO has a chain length of 24 to 96 carbon atoms on average.

[0088] 44. The functionalised polyolefin of any preceding clause, wherein PO has a chain length of 26 to 92 carbon atoms on average.

[0089] 45. The functionalised polyolefin of any preceding clause, wherein PO has a chain length of 30 to 90 carbon atoms on average. 46. The functionalised polyolefin of any preceding clause, wherein PO has a chain length of 34 to 88 carbon atoms on average.

[0090] 47. The functionalised polyolefin of any preceding clause, wherein PO has a chain length of 38 to 86 carbon atoms on average.

[0091] 48. The functionalised polyolefin of any preceding clause, wherein PO has a chain length of 42 to 84 carbon atoms on average.

[0092] 49. The functionalised polyolefin of any preceding clause, wherein PO has a chain length of 46 to 82 carbon atoms on average.

[0093] 50. The functionalised polyolefin of any preceding clause, wherein PO has a chain length of 50 to 80 carbon atoms on average.

[0094] 51 . The functionalised polyolefin of any preceding clause, wherein PO has a chain length of 54 to 76 carbon atoms on average.

[0095] 52. The functionalised polyolefin of any preceding clause, wherein PO has a chain length of 60 to 70 carbon atoms on average.

[0096] 53. The functionalised polyolefin of any preceding clause or any of clauses 55-57, wherein the functionalised polyolefin exhibits antimicrobial activity against gram-negative bacteria.

[0097] 54. The functionalised polyolefin of clause 53, wherein the gram-negative bacteria is E. coli.

[0098] 55. A functionalised polyolefin of formula PO-X, wherein:

[0099] PO is a polyolefin having a chain length of at least 20 carbon atoms; and

[0100] X is an antimicrobially active polar moiety.

[0101] 56. A functionalised polyolefin of formula PO-X, wherein:

[0102] PO is a polyolefin having a chain length of at least 20 carbon atoms on average; and

[0103] X is a positively charged functional group or a functional group capable of forming a cation at pH 7.

[0104] 57. A functionalised polyolefin of formula PO-X, wherein:

[0105] PO is a polyolefin having a chain length of at least 20 carbon atoms on average; and

[0106] X is an antimicrobially active polar moiety.

[0107] 58. The functionalised polyolefin of any of clauses 55-57, wherein PO and / or X is as defined in any of clauses 2-52. 59. A process for preparing the functionalised polyolefin of any one of clauses 1-58, the process comprising: reacting Zn(PO)2 with iodine to obtain PO-I; and reacting PO-I to obtain PO-X, wherein PO has a chain length of at least 20 carbon atoms.

[0108] 60. The process of clause 59, wherein Zn(PO)2 is produced by polymerising an olefin in the presence of a zinc alkyl and a catalyst system.

[0109] 61 . The process of clause 60, wherein the zinc alkyl is ZnEt2.

[0110] 62. The process of clause 59 or 60, wherein the olefin is selected from ethylene and propylene.

[0111] 63. The process of clause 62, wherein the olefin is ethylene.

[0112] 64. The process of clause 62, wherein the olefin is propylene.

[0113] 65. The process of any of clauses 60-64, wherein the catalyst system comprises a group 3-10 transition metal, a group 3 main group metal, a lanthanide, or an actinide.

[0114] 66. The process of any of clauses 60-65, wherein the catalyst system comprises iron.

[0115] 67. The process of any of clauses 60-66, wherein the catalyst system comprises bis(imino)pyridine.

[0116] 68. The process of any of clauses 60-67, wherein the catalyst system comprises [(2,6- diacetylpyridinebis(2,6-diisopropylanil))FeCl2].

[0117] 69. The process of any of clauses 60-68, wherein the catalyst system further comprises methylaluminoxane (MAO).

[0118] 70. The process of any of clauses 61-69, wherein the ratio of Zn as present in ZnEt2 to Fe as present in the catalyst system is 270 to 500 molar equivalents.

[0119] 71 . The process of clause 70, wherein the ratio of Zn as present in ZnEt2 to Fe as present in the catalyst system is 300 to 450 molar equivalents.

[0120] 72. The process of any of clauses 59-71 , wherein reacting PO-I to obtain PO-X comprises reacting PO-I with a tertiary amine. 73. The process of clause 72, wherein the tertiary amine is dimethylbenzylamine.

[0121] 74. The process of clause 72 or 73, wherein the reaction with the tertiary amine is carried out in butanone.

[0122] 75. The process of clause 72 or 73, wherein the reaction with the tertiary amine is carried out by refluxing in the tertiary amine, optionally wherein PO has a chain length of 50 to 80 carbon atoms or 50 to 80 carbon atoms on average.

[0123] 76. The process of any of clauses 59-71 , wherein reacting PO-I to obtain PO-X comprises reacting PO-I with a pyridine.

[0124] 77. The process of clause 76, wherein the pyridine is pyridine.

[0125] 78. The process of clause 76 or 77, wherein the reaction with the pyridine is carried out in toluene, butanone, 1 ,2,4-trichlorobenzene or N,N-dimethylformamide.

[0126] 79. The process of clause 76 or 77, wherein the reaction with the pyridine is carried out by refluxing in the pyridine, optionally wherein PO has a chain length of 50 to 80 carbon atoms or 50 to 80 carbon atoms on average.

[0127] 80. The process of any of clauses 59-71 , wherein reacting PO-I to obtain PO-X comprises: reacting PO-I with an azide to obtain PO-N3; reducing the azide to obtain PO-NH2; and reacting PO-NH2 with a cyanoguanidine.

[0128] 81 . The process of clause 80, wherein reducing the azide is carried out using LiAIF .

[0129] 82. The process of clause 80, wherein reducing the azide is carried out using H2 and Pd / C.

[0130] 83. The process of any of clauses 59-71 , wherein reacting PO-I to obtain PO-X comprises: reacting PO-I with NH3 to obtain PO-NH2; and reacting PO-NH2 with a cyanoguanidine.

[0131] 84. The process of clause 83, wherein NH3 is provided in excess.

[0132] 85. The process of clause 83 or 84, wherein the reaction between PO-I and NH3 is carried out in toluene. 86. The process of any of clauses 83-85, wherein the reaction between PO-NH2 and cyanoguanidine is carried out in n-butanol.

[0133] 87. The process of any of clauses 83-86, wherein the cyanoguanidine is p-chlorophenyl cyanoguanidine.

[0134] 88. The process of any of clauses 59-71 , wherein reacting PO-I to obtain PO-X comprises reacting PO-I with a tertiary phosphine.

[0135] 89. The process of clause 88, wherein the tertiary phosphine is PPhs.

[0136] 90. The process of clause 88, wherein the tertiary phosphine is PBus.

[0137] 91 . The process of any of clauses 88-90, wherein the reaction with the tertiary phosphine is carried out in toluene.

[0138] 92. A functionalised polyolefin obtainable by the process of any one of clauses 59-91 .

[0139] 93. A polyolefin blend comprising a first polyolefin and a second polyolefin, wherein the first polyolefin is a functionalised polyolefin as defined in any one of clauses 1 -58 or 92.

[0140] 94. The polyolefin blend of clause 93, wherein the first polyolefin is provided at a loading of at least 0.01 wt% relative to the total mass of the polyolefin blend.

[0141] 95. The polyolefin blend of clause 93 or 94, wherein the first polyolefin is provided at a loading of at least 0.05 wt% relative to the total mass of the polyolefin blend.

[0142] 96. The polyolefin blend of any of clauses 93-95, wherein the first polyolefin is provided at a loading of at least 0.1 wt% relative to the total mass of the polyolefin blend.

[0143] 97. The polyolefin blend of any of clauses 93-96, wherein the first polyolefin is provided at a loading of at least 0.5 wt% relative to the total mass of the polyolefin blend.

[0144] 98. The polyolefin blend of any of clauses 93-97, wherein the first polyolefin is provided at a loading of at least 0.75 wt% relative to the total mass of the polyolefin blend.

[0145] 99. The polyolefin blend of any of clauses 93-98, wherein the first polyolefin is provided at a loading of at least 1 wt% relative to the total mass of the polyolefin blend. 100. The polyolefin blend of any of clauses 93-99, wherein the first polyolefin is provided at a loading of at least 1.25 wt% relative to the total mass of the polyolefin blend.

[0146] 101. The polyolefin blend of any of clauses 93-100, wherein the first polyolefin is provided at a loading of at least 1.5 wt% relative to the total mass of the polyolefin blend.

[0147] 102. The polyolefin blend of any of clauses 93-101 , wherein the first polyolefin is provided at a loading of at least 1.75 wt% relative to the total mass of the polyolefin blend.

[0148] 103. The polyolefin blend of any of clauses 93-102, wherein the first polyolefin is provided at a loading of at least 2 wt% relative to the total mass of the polyolefin blend.

[0149] 104. The polyolefin blend of any of clauses 93-103, wherein the first polyolefin is provided at a loading of at most 4 wt% relative to the total mass of the polyolefin blend.

[0150] 105. The polyolefin blend of any of clauses 93-104, wherein the first polyolefin is provided at a loading of at most 3.5 wt% relative to the total mass of the polyolefin blend.

[0151] 106. The polyolefin blend of any of clauses 93-105, wherein the first polyolefin is provided at a loading of at most 3 wt% relative to the total mass of the polyolefin blend.

[0152] 107. The polyolefin blend of any of clauses 93-106, wherein the first polyolefin is provided at a loading of at most 2.5 wt% relative to the total mass of the polyolefin blend.

[0153] 108. The polyolefin blend of any of clauses 93-107, wherein the first polyolefin is provided at a loading of at most 2 wt% relative to the total mass of the polyolefin blend.

[0154] 109. The polyolefin blend of any of clauses 93-108, wherein the first polyolefin is provided at a loading of at most 1 .75 wt% relative to the total mass of the polyolefin blend.

[0155] 110. The polyolefin blend of any of clauses 93-109, wherein the first polyolefin is provided at a loading of at most 1 .5 wt% relative to the total mass of the polyolefin blend.

[0156] 111. The polyolefin blend of any of clauses 93-110, wherein the first polyolefin is provided at a loading of at most 1 .25 wt% relative to the total mass of the polyolefin blend.

[0157] 112. The polyolefin blend of any of clauses 93-111 , wherein the first polyolefin is provided at a loading of at most 1 wt% relative to the total mass of the polyolefin blend. 113. The polyolefin blend of any of clauses 93-112, wherein the first polyolefin is provided at a loading of at most 0.75 wt% relative to the total mass of the polyolefin blend.

[0158] 114. The polyolefin blend of any of clauses 93-113, wherein the first polyolefin is provided at a loading of at most 0.5 wt% relative to the total mass of the polyolefin blend.

[0159] 115. The polyolefin blend of any of clauses 93-114, wherein the first polyolefin is provided at a loading of 0.01 wt% to 4 wt% relative to the total mass of the polyolefin blend.

[0160] 116. The polyolefin blend of any of clauses 93-115, wherein the first polyolefin is provided at a loading of 0.05 wt% to 3 wt% relative to the total mass of the polyolefin blend.

[0161] 117. The polyolefin blend of any of clauses 93-116, wherein the first polyolefin is provided at a loading of 0.1 wt% to 2.5 wt% relative to the total mass of the polyolefin blend.

[0162] 118. The polyolefin blend of any of clauses 93-117, wherein the first polyolefin is provided at a loading of 0.5 wt% to 2 wt% relative to the total mass of the polyolefin blend.

[0163] 119. The polyolefin blend of any of clauses 93-118, wherein the first polyolefin is provided at a loading of 1 wt% to 2 wt% relative to the total mass of the polyolefin blend.

[0164] 120. The polyolefin blend of any of clauses 93-119, wherein the first polyolefin is provided at a loading of about 2 wt% relative to the total mass of the polyolefin blend.

[0165] 121. The polyolefin blend of any of clauses 93-120, wherein the second polyolefin is selected from polyethylene (PE), polypropylene (PP), and mixtures thereof.

[0166] 122. The polyolefin blend of clause 121 , wherein the second polyolefin is PE.

[0167] 123. The polyolefin blend of clause 122, wherein PO is PE and the second polyolefin is PE.

[0168] 124. A process for preparing the polyolefin blend of any one of clauses 93-123, the process comprising melt blending the first polyolefin with the second polyolefin.

[0169] 125. The process of clause 124, wherein the melt blending is carried out via co-extrusion.

[0170] 126. The process of clause 124 or 125, wherein the melt blending is carried out at 100 °C to 200 °C. 127. The process of any of clauses 124-126, wherein the melt blending is carried out at 120 °C to 150 °C.

[0171] 128. The process of any of clauses 124-127, wherein the melt blending is carried out at 130 °C.

[0172] 129. Use of a functionalised polyolefin as defined in any one of clauses 1-58 or 92 as an antimicrobial polymer additive.

[0173] 130. A method for imparting antimicrobial properties to a surface, the method comprising applying a functionalised polyolefin as defined in any one of clauses 1-58 or 92 or a polyolefin blend according to any one of clauses 93-123 to the surface.

[0174] 131. The method of clause 130, wherein the functionalised polyolefin or polyolefin blend is applied in the form of a film.

[0175] 132. A surface or article comprising (i) a functionalised polyolefin as defined in any one of clauses 1-58 or 92 or (ii) a polyolefin blend according to any one of clauses 93-123.

[0176] 133. The article of clause 132, wherein the article is a medical device.

[0177] 134. The article of clause 133, wherein the medical device is a catheter.

[0178] The present invention will now be described by way of reference to the following examples and accompanying drawings which are present for the purposes of illustration only and are not to be construed as being limiting on the invention.

[0179] EXAMPLES

[0180] Example 1. Catalysed chain growth (CCG) reaction

[0181] Long chain 1-iodo alkanes were prepared via a CCG reaction starting from diethyl zinc and ethylene. An example of this is shown in Scheme 1 . The bis(imino)pyridine iron complex was activated with MAO to insert ethylene monomers into the C-Zn bond of ZnEt2, resulting in a narrow molecular weight distribution of ZnPE2.

[0182] Scheme 1 Preparation of Zn(PE>2

[0183] Zn(PE)2 was prepared as described in W003014046. (2,6-diacetylpyridinebis(2,6- diisopropylanil))FeCl2 (6.5 mg, 0.01 mmol) was placed in 5 ml toluene resulting in a blue suspension. After the addition of 100 equivalents of MAO (0.93 ml of 7 wt% sol. in toluene), the solution turned orange. To the orange solution was added ZnEt2 dissolved in 25 ml of toluene (3 mmol, 2.63 ml of 15 wt.% solution in toluene), resulting in a yellow solution. The polymerisation was started by the addition of ethylene (1 bar(g)) at room temperature. After the desired time (typically less than 1 hour), the polymerisation was stopped by closing the ethylene supply and the resulting precipitate was filtered resulting in 1.94 g of Zn(PE)2 polymer, after multiple washes with toluene under N2. Contamination with PE due to partial hydrolysis during workup is often observed, and it is recommended to convert Zn(PE)2 in situ, without isolation.1H-NMR (400 MHz, da-toluene, 100 °C): 5 1 .53 (m, ZnCH2C / 2), 1 .36 (C / 2), 0.83 (C / 3), 0.30 (t, J = 8Hz, ZnCH2).13C NMR (400 MHz, d8-toluene, 100 °C): 37.1 (ZnCH2CH2), 26.8 (CH2CH3), 16.3 (ZnCH2), 14.2 (CH3). IR (ATR, neat): cm1291 1 (vCHas), 2846 (vCHs), 1467 (6CH2), 1379 (6CH3), 717 (6CH2), 625 (pZnCH2).

[0184] Preparation of PE-I

[0185] Zn(PE)2 (28 mg, 0.028 mmol, Zn(C34He9)2) was suspended in 10 ml toluene. A solution of iodine (14.2 mg, 0.056 mmol, 2 equiv.) in 5 ml of toluene was added to the mixture over 1 h at room temperature. The reaction was kept at 60 °C for 1 h. The reaction was quenched by the addition of the reaction mixture to 20 ml methanol and 1 ml of 1 M aqueous HCI solution. The precipitate was filtered and dried to yield the product polymer (16 mg, 48% yield). The product was analysed by1H which indicated 84% iodine-functionalisation.1H-NMR (400 MHz, CDCI3, 25 °C): 5 3.19 ppm (t, 2H,3JH-H = 7 Hz, CH2-I), 1.82 ppm (m, 2H, CH2-CH2-I), 1.25 ppm (s, 67H, -CH2-), 0.88 ppm (t, 3H,3JH-H = 7 Hz, -CH3).

[0186] Example 2. Chain length variations in Zn(PE)2 at different Zn / Fe ratios

[0187] The CCG reaction provides full control of the chain length of the growing alkane via adjusting the Zn / Fe ratio.

[0188] In the absence of the chain transfer agent ZnEt2, the catalyst system polymerises ethylene with very high activity and produces high molecular weight polyethylene (run 1 in Table 1). At Zn / Fe ratios of >300 equiv., catalysed chain growth to form Zn(PE) is observed. While larger Zn / Fe ratios will produce more Zn(PE)2, this results in shorter chains within a given time and also lowers the catalytic activity, probably due to competitive binding of ZnEt2 versus ethylene to the catalyst. Table 1 . Chain length variations in Zn(PE)2 at different Zn / Fe ratios.

[0189] ZnEt2ZnEt2Activity

[0190] Run [mmol] Equiv. [g mmol”1h bar"1]aCnb

[0191] 1 0 0 PEC—

[0192] 2 2.5 250 PEC

[0193] 3 3.0 300 1380 31 64

[0194] 4 3.5 350 1420 21 44

[0195] 5 4.0 400 820 14 30

[0196] 6 4.5 450 600 11 24

[0197] 7 5.0 500 690 8 18

[0198] 8 5.5 550 482 7 16

[0199] 9 6.0 600 500 4 10

[0200] Conditions: catalyst (10 pmol), MAO (100 eq.), toluene solvent (30 mL), room temperature, 1 barg ethylene, 1 hour reaction time.aA = mean number of ethylene units inserted, determined by GC analysis.bCn= mean chain length, determined by13C-NMR analysis.cNo exchange to zinc is observed.

[0201] Example 3. Synthesis of antimicrobial additives

[0202] PE-N-(4-chlorophenyl)-N'-alkylimidodicarbonimidic diamide (PE-CH), PE-dimethylbenzylammonium iodide (PE-DMBA), and PE-pyridinium iodide (PE-PYR) were synthesized as illustrated in Scheme 2.

[0203] PE-triphenylphosphonium iodide and polyethylene-tributylphosphonium iodide were also synthesised. Synthesis of p-chlorophenyl cyanoguanidine

[0204] 0.7 g of sodium dicyanamide (7.84 mmol) and 1 .0 g of 4-chloroaniline (7.84 mmol) were dissolved in 40 ml of water. 0.7 ml of HCI (aq, 37%, 7.8 mmol) was added to the aqueous solution, and the mixture was left to stir for 3 hours at 60 °C. The mixture was then cooled to 0 °C resulting in white powder. The product was filtered over a filter paper and washed with 50 ml of ether, resulting in 1 .36 g of white powder (90 % yield).1H NMR (500 MHz, DMSO, 393 K) 6 6.64 (s, 2H), 7.33 (d, J = 7.5 Hz, 2H), 7.36 (d, J = 7.3 Hz, 2H), 8.83 (s, 1 H).13C NMR (101 MHz, DMSO) 6 117.42, 123.28, 127.92, 129.12, 137.53, 159.89 ppm.

[0205] Synthesis of PE-NH2

[0206] PE-I can be converted to PE-NH2 using a two-step protocol via PE-N3 and subsequent reduction, either with IJAIH4, or using H2 and Pd / C. The latter method, which was used to prepare PE-N-(4- chlorophenyl)-N'-alkylimidodicarbonimidic diamide as used in the examples herein, works well for shorter alkyl chains that can easily be dissolved in hot toluene and separated from the catalyst by filtration, but this may become a problem for larger alkyl chains. A more convenient one-step method may be used. This avoids the use of azides and IJAIH4 altogether and involves simply reacting PE-I with an excess of liquid ammonia at elevated temperature and pressure in toluene. An excess of ammonia is needed to avoid over-alkylation.

[0207] Option 1. Two-step synthesis of PE-NH2

[0208] Approximately 1 g of PE-I (CaoHe?-!, ~1.8 mmol, 1 equiv.) and 0.14 g of sodium azide (2.2 mmol, 1.2 equiv.) were added to 20 mL of DMF. The reaction was purged with nitrogen and stirred at 120 °C for 4 hours. Subsequently, the suspension was filtered, washed with methanol, and dried under vacuum overnight, resulting in 0.75 g of PE-N3 as a white powder (90% yield). C30H61-N3 functionality was confirmed by FTIR spectroscopy with a peak at 2094 cm-1(N3) and quantified by1H NMR spectroscopy.1H NMR (500 MHz, d2-TCE / 1 ,2,4- trichlorobenzene, 363K) 6 1 .03 - 1 .07 (t, J = 6.8 Hz, 3H), 1 .35 - 1 .56 (d, J = 4.0 Hz, 72H), 1 .70 - 1 .75 (m, 2H), 3.33 - 3.38 (t, J = 6.9 Hz, 2H) ppm.13C NMR (500 MHz, d2- TCE / 1 ,2,4- trichlorobenzene, 363K) 5 12.81 , 21 .59, 27.74 - 28.53 (m), 28.69, 29.08, 30.90, 50.68 ppm.

[0209] 0.5 g of PE-N3 (CaoHeiNa, ~1 mmol), 20 mg of Pd / C, and 10 mL of toluene were added to a 100 mL Hastelloy Parr reactor. The reactor was sealed, purged with nitrogen, and set to a pressure of 10 bar of hydrogen at room temperature. The reaction was stirred for 20 hours at room temperature. The reaction mixture, dissolved in toluene, was heated to 80 °C, followed by a hot filtration over a glass fiber filter to remove the Pd / C catalyst. The filtrate was then cooled to room temperature, poured into methanol, resulting in PE-NH2 as a white powder precipitate. The white powder was washed with methanol and dried under vacuum overnight. Yield: 0.42 g (85%). CaoH6)-NH2 purity was confirmed by FTIR showing the disappearance of the azide peak at 2094 cm-1(N3) and the appearance of the amine peak at 3333 cm'1(NH stretch) and quantified by1H NMR (500 MHz, d2-TCE / 1 ,2,4- trichlorobenzene, 363K) 5 0.84 - 0.91 (m, 3H), 1 .22 - 1 .43 (s, 22H), 2.53 - 2.61 (t, J = 6.7 Hz, 2H) ppm.13C NMR (500 MHz, d2-TCE / 1 ,2,4- trichlorobenzene, 363K) 5 12.81 , 21 .58, 25.79, 27.78 - 29.71 (m), 30.89, 39.08 ppm. Option 2. One-step synthesis of PE-NH2

[0210] 700 mg of PE-I (C42H85-I, ~1 mmol) was weighed and transferred into a 100 mL Hastelloy Parr autoclave. This was followed by the addition of 20 ml of toluene and 30 ml (approximately 1200 mmol) of liquid ammonia (cooled at -33 °C) into the autoclave, while the reaction vessel was kept cool in a dry ice / acetone bath. The autoclave was sealed, allowed to warm to room temperature and gradually heated to 60 °C while stirring. The pressure in the autoclave reached 20 bars when the system was at 60 °C. After 10 hours, the autoclave was cooled to room temperature, and the pressure was gradually released. The mixture was poured into methanol to give a white precipitate. The white solid was filtered and washed with 50 ml of methanol. The final product was collected and dried in a vacuum oven at 40 °C overnight. The mass of the product was 494 mg (83% yield) and a 92% purity of PE-NH2 (a small amount of (PE)2NH is also observed, ~8 % by1H NMR spectroscopy).

[0211] Synthesis of N-(4-chlorophenyl)-N'-alkylimidodicarbonimidic diamide (PE-CH)

[0212] 5.3 mmol of CnH2n+i-NH2, 5.3 mmol of p-chlorophenyl cyanoguanidine, 5.3 mmol of HCI, and 50.0 ml of butanol were added to a round bottom flask. The mixture was stirred at 150 °C overnight under reflux. The product was isolated by removing butanol under vacuum and washing the powder using diethyl ether three times, resulting in white powder.1H NMR (500 MHz, DMSO, 393K) 5 0.82 - 0.99 (m, 3H), 1 .11 - 1 .41 (m), 1 .57 - 1 .71 (m, 2H), 2.76 - 2.85 (m, 2H), 6.87 (s, 2H), 7.22 - 7.35 (d, J = 7.5 Hz, 2H), 7.38 - 7.50 (d, J = 7.4 Hz, 2H), 7.98 (s, 3H).13C NMR (126 MHz, DMSO) 5 12.89, 17.88, 21.19, 28.20, 30.50, 34.04, 39.34, 122.58, 127.52, 136.52, 145.24, 156.38 ppm.

[0213] Synthesis of alkyl pyridinium iodide (PE-PYR)

[0214] 3.0 g of C68-H137-I (2.78 mmol) was refluxed in 20 ml of pyridine at 150 °C for 48 hours, resulting in an orange solution. After cooling to room temperature, the product was filtered over a filter paper, affording green solids, which was then washed three times with 30 ml of methanol and placed in a vacuum oven at 40 °C overnight. The product was then ground, resulting in 2.4 g of a pale green powder (78% yield).1H NMR (500 MHz, d2-TCE / 1 ,2,4-trichlorobenzene1 / 2v / v, 393K) 5 1 .07 (t, J = 6.6 Hz, 3H), 1 .47 (m, 86H), 2.27 (m, 4H), 5.10 (t, J= 4.8Hz, 2H), 8.38 (m, 2H), 8.84 (m, 1 H), 9.50 (d, J = 7.5 Hz, 2H).13C NMR (101 MHz, d2-TCE / 1 ,2,4-trichlorobenzene1 / 2v / v, 393K) 5 12.70, 21.67, 23.55, 25.80, 28.12, 29.19, 31.02,53.84, 59.94, 131.12, 145.43, 148.32.

[0215] Synthesis of PE-dimethylbenzylammonium iodide (PE-DMBA)

[0216] 3.0 g of C68-H137-I (2.78 mmol) was refluxed in 20 ml of N,N-dimethyl benzylamine at 150 °C for 48 hours, resulting in a black solution. The reaction mixture was then cooled to room temperature, and the product was filtered over filter paper. The product was washed three times with 30 ml of methanol and dried in a vacuum oven overnight, resulting in 2.6 g of brown powder (76% yield).1H NMR (500 MHz, d2-TCE / 1 ,2,4-trichlorobenzene1 / 2v / v, 393K) 5 1 .06 (t, J = 7.0 Hz, 3H), 1 .47 (m, 75H), 1 .86 - 2.12 (m, 2H), 2.84 (s, 6H), 2.99 - 3.15 (m, 2H), 7.49 (m, 5H).13C NMR (101 MHz, d2-TCE / 1 ,2,4- trichlorobenzene1 / 2v / v, 393K) 5 12.80, 21.57, 23.05, 25.90, 28.02, 29.09, 30.88, 41.44, 49.10, 56.97, 73.27, 1 15.54, 122.90, 144.32.

[0217] Synthesis of PE-triphenylphosphonium iodide

[0218] Under a nitrogen atmosphere, PE-I (C60H121I, 0.91 g, approx. 1.0 mmol) and an excess PPhs (1.31 g, 5.0 mmol) were dissolved in toluene (10 mL). The reaction mixture was heated under reflux at 120 °C for 48 hours and then quenched with methanol (100 mL), resulting in a white solid, which was collected by filtration, washed with methanol and dried under vacuum (0.84 g, 0.72 mmol, 72 % yield).1H NMR (70 °C, 400 MHz, C6D6 / tetrachloroethene (1 / 2 vol / vol)): 5 = 0.84 (3H, t, CH3, J = 8 Hz), 1 .25 (m, CH2), 4.2 (m, 2H, PCH2), 6.96-7.95 (15H, m) ppm.31P{1H} NMR (70 °C, 162 MHz, C6D6 / tetrachloroethene (1 / 2 vol / vol)): 5 = 25.29 ppm.

[0219] Synthesis of PE-tributylphosphonium iodide

[0220] Under a nitrogen atmosphere, PE-I (C60H121I, 0.91 g, approx. 1.0 mmol) and PBus (1.25 mL, 5.0 mmol) were dissolved in toluene (10 mL). The reaction mixture was heated under reflux at 120 °C for 48 hours and then quenched with methanol (100 mL), resulting in a white solid which was collected by filtration, washed with methanol and dried under vacuum (0.62 g, 0.56 mmol, 56 % yield).

[0221] 1H NMR (120 °C, 400 MHz, d2-tetrachloroethane / 1 ,2,4-trichlorobenzene (1 / 2, vol / vol)): 5 = 1.05 (3H, t, CH3, J = 4 Hz), 1.16 (9H, t, J= 4 Hz), 1 .47 (m), 2.66 (8H, m) ppm.31P{1H} NMR (120 °C, 162 MHz, d2- tetrachloroethane / 1 ,2,4-trichlorobenzene (1 / 2, vol / vol)): 5 = 33.44 ppm.

[0222] Example 4. Conversion of PE-NH2 to PE-CH

[0223] Different molecular weights of amino end-functionalized PE (PE-NH2), ranging from C12 to Ces, have been used to prepare the PE-CH additive. The overall functionality of PE-CH decreases as the molecular weight of the alkyl chains increases due to the lower solubility of the long alkyl chains in butanol (Table 2). The conversion of PE-NH2to PE-CH ranges from 90% for Ci2H25-NH2to 85% for C6sHi37-NH2, resulting in 90% functionality for CI2H25-CH and C18H37-CH, 85% functionality for C30H61- CH and 75% functionality for C68H137-CH.

[0224] Table 2. Synthesis of N-(4-Chlorophenyl)-N'-alkylimidodicarbonimidic diamide (PE-CH).

[0225] Cn= average chain length, determined by13C NMR spectroscopy analysis, a) Functionality yield determined by1H NMR spectroscopy analysis. Conversion = PE-CH functionality (%) / PE-NH2 functionality (%).

[0226] Example 5. Conversion of PE-I to PE-PYR

[0227] A nucleophilic substitution (SN2) reaction was utilized to produce different molecular weights of alkyl pyridinium iodide (PE-PYR). Reacting C18H37-I with pyridine using toluene as a solvent afforded 86% conversion, while changing the solvent to butanone resulted in 90% conversion. The slight increase in the conversion using butanone as a solvent could result from the change in the polarity of the solvent. SN2 reactions are sensitive toward solvents, and polar aprotic solvents show generally higher conversion rates.

[0228] When longer alkyl chains were used, such as C68H137-I, the reaction was unsuccessful using butanone, 1 ,2,4-trichlorobenzene or N,N-dimethylformamide. These solvents were employed due to their ability to dissolve the long alkyl chains at higher temperature. Since the SN2 reaction rate depends on the concentration of both PE-I and pyridine, a higher reagent concentration could result in better conversion. Thus, C68H137-I was refluxed in pyridine at 150 °C, affording 90% conversion and 81 % functionalization of the PE-PYR. Increasing the alkyl chain length of PE-I to 180 carbons resulted in 36% conversion and only 30% functionality of PE-PYR due to the low solubility of PE chains in pyridine. Table 3. Synthesis of alkyl pyridinium iodide (PE-PYR). a) Functionality percentage determined by1H NMR spectroscopy analysis, b) Conversion= PE-PYR functionality (%) / PE-I functionality (%). Average chain length of PE-I was determined by13C NMR.

[0229] Example 6. Conversion of PE-I to PE-DMBA

[0230] The synthesis of n-alkyl dimethyl benzyl ammonium iodide was carried out by the reaction of N,N- dimethyl benzylamine with different molecular weights of PE-I.

[0231] Butanone has been reported multiple times for its ability to accomplish SN2 reactions. However, the solubility of the long functionalized alkanes in butanone is low. Thus, the reaction of C68H137-I with N,N-dimethyl benzylamine was unsuccessful when butanone was used as a solvent. The result was similar when 1 ,2,4-trichlorobenzene or N,N-dimethylformamide were used as solvents for the reaction. Since the SN2 reaction rate depends on the concentration of the reactants, C68H137-I was refluxed in pure N,N-dimethyl benzylamine at 150 °C, resulting in 82% conversion and 80 % functionality. In contrast, refluxing C180H361-I in N,N-dimethyl benzylamine at 150 °C afforded only 36% conversion and 30% functionality of PE-DMBA.

[0232] Table 4. Synthesis of PE-dimethylbenzylammonium iodide (PE-DMBA). a) Functionality yield determined by1H NMR spectroscopy analysis, b) Conversion = PE-DMBA functionality (%) / PE-I functionality (%). Average chain length of PE-I was determined by13C NMR spectroscopy analysis.

[0233] Example 7. Extrusion and thermal analysis

[0234] Melt blending of LDPE with antimicrobial PE additives

[0235] Melt blending of LDPE with antimicrobial PE additives was carried using a co-rotating twin-screw extruder (Eurolab XL, Thermo Fisher Scientific, Karlsruhe, Germany). The twin-screw extruder is equipped with a diameter of 16 mm and a length to diameter ratio of 25. The feeding zone of the extruder, the four subsequent zones, and the die temperatures were set to 130 °C during the fabrication of the LDPE / additives blends. The extrusions were processed at a speed of 15 rpm for the first cycle, 30 rpm for the second cycle, and 50 rpm for the third cycle. After each cycle, the extrudate was pelletized into 2 mm granules using a cutter (Haake VariCut, Thermo Fisher Scientific, Karlsruhe, Germany), mixed in a container, and fed into the extruder for the next cycle.

[0236] Extrusion of LDPE / PE-CH

[0237] The extrusion of 10 g of LDPE with 0.4 g of C66H133-CH was processed using a co-rotating twin-screw extruder (Eurolab XL, Thermo Fisher Scientific, Karlsruhe, Germany). The two materials where first mixed in a container and then fed into the extruder. The feeding zone of the extruder, the four subsequent zones, and the die temperatures were set to 130 °C during the fabrication of the LDPE / PE-CH blends. The extrusions were processed at a speed of 15 rpm for the first cycle, 30 rpm for the second cycle, and 50 rpm for the third cycle. After each cycle, the molten extrudate was left to recrystallize under air and then was pelletized into 2 mm granules using a cutter (Haake VariCut, Thermo Fisher Scientific, Karlsruhe, Germany), mixed in a container, and fed into the extruder for the next cycle. Table 5 shows the melt blending of antimicrobial additives with LDPE using different additive loadings (wt%).

[0238] Table 5. Melt blending of antimicrobial additives with LDPE.

[0239] Differential Scanning Calorimetry (DSC)

[0240] DSC measurements were carried out using a Discovery DSC (TA Instruments, Hertfordshire, UK) to evaluate the thermal behaviour of the LDPE and the additives under a nitrogen atmosphere. 2-5 mg samples were used for each measurement. The samples were heated from 0-200 °C at a rate of 10 °C / min, then cooled at a rate of 10 °C / min. The sample was reheated to 200 °C at a rate of 10 °C / min. The data was processed using Trios software.

[0241] The crystallinity percentage of LDPE and the antimicrobial LDPE blends was measured using the second heating cycle of the DSC analysis. The crystallinity was determined by quantifying the heat of fusion (AHm) associated with the melting stage and normalized to the heat of fusion of 100% crystalline polyethylene (A Ho) according to the equation: 100 where AHmis the heat of fusion (J / g), AHois the heat of fusion of 100% crystalline PE (293 J / g), and w is the fraction of LDPE in the blend.

[0242] Table 6 displays the experimental data obtained from the DSC analysis of the samples. The second heating cycle in the DSC scans was considered since a controlled crystallization was carried out in the first cooling cycle. This allows a more accurate comparison of the samples’ crystallinities. The pure LDPE showed 32.3% crystallinity and in general, a lowering of the crystallinity is observed upon the addition of the additives. LDPE blends with C66H133-CH and C18H37-CH showed a similar behaviour, whereby the crystallinity of the 2 wt% loading is higher than that of 4 wt% loading (Table 6). Increasing the alkyl chain length from C18 to Cee showed slightly higher crystallinity of the blends. A 2 wt% loading of PE-PYR and PE-DMBA into LDPE showed very little change in the crystallinity percentage, while 4 wt% loading of PE-DMBA decreased the crystallinity from 32.3 to 21 .8%. In general, the addition of the antimicrobial additives into LDPE showed a minimum impact on the melting temperature and the crystallinity of the LDPE, which indicate minimal change to the mechanical properties of the polymer.

[0243] Table 6. DSC measurements for LDPE and LDPE / antimicrobial PE additives blends via melt blending using the second heating cycle.

[0244] TGA

[0245] TGA analysis was also carried out to evaluate the impact of adding additives into LDPE on the degradation temperature. The thermal degradation measurements were carried out using Mettler Toledo TGA. 5-10 mg samples were used for each measurement. The temperature was ramped up from room temperature to 800 °C at a rate of 10 °C / min under a nitrogen atmosphere.

[0246] Further TGA measurements were carried out in which the degradation temperatures were increased from 435 °C by 20-50 °C in all cases. The results suggest that no negative impact on the thermal degradation of the blends has occurred. Example 8. Extraction experiments

[0247] In order to study the entanglement of the antimicrobial additives into LDPE, several extraction attempts have been carried out using two different approaches.

[0248] Additives extraction using agitation.

[0249] 1 g of LDPE / C18H37-CH blend with 4 wt.% loading was pressed into a film with 1 .5 mm thickness. The film was then placed into a vial with magnetic stirrer. The extraction was carried out using hexane at room temperature for 24 hours. The collected extract was then placed under vacuum to remove the volatiles. No precipitate was collected using this extraction method.

[0250] Additives extraction using Soxhlet.

[0251] 1 g of LDPE / C18H37-CH blend with 4 wt.% loading was pressed into a film with 1 .5 mm thickness. The film was then placed into a thimble for Soxhlet extraction. The extraction was carried out using hexane at 80 °C for 5 hours. Hot toluene at 80 °C was then used to wash the sample and dissolve any leached additives. A control experiment proved that hot toluene at 80 °C dissolves the antimicrobial additives and can go through the Soxhlet thimble. The collected extract was then placed under vacuum to remove the volatiles. In this case when LDPE / C18H37-CH blend with 4 wt.% loading was used, 9 mg of the additives was collected, accounting for 22.5 % of the total additives in the sample. The collected additives were then characterized by FTIR spectroscopy to confirm the vibrational bands of C18H37-CH with C=N stretch at 1634 cm1, C-N stretch at 1250 cm1and N-H bond vibration at 3100- 3500 cm1.

[0252] The extractions following the first approach did not show any leaching of the additives as no extract was collected. In the second approach where a Soxhlet was used, the leaching of additives was observed when LDPE-CISH37-CH-4% was subjected to hexane extraction at 80 °C for 5 hours. In order to ensure that leached additives will go through the thimble, hot toluene at 80 °C was used to wash the sample. Leaching of the additives was only observed when the active antimicrobial agents synthesized on C18. The amount of additives leached was 23% of the total additives loading (Table 7). When LDPE-CnH2n+i-CH blends were used with n=30 and 66, no residue was collected. Increasing the loading of the C66H133-CH to 10% did not show any leaching of the additive. FTIR spectroscopy measurements of the blends after extraction confirm the additive's presence with vibrational bands of C=N stretch at 1634 cm-1and C-N stretch at 1250 cm1. The Soxhlet extraction was also carried out for LDPE-C66H 133-PYR with 4 wt% loading. Also in this case, no leaching of the additives from the LDPE matrix was observed. FT-IR spectroscopy confirmed the presence of the additives with vibrational bands of C=N stretch at 1634 cm1, aromatic C-N stretch at 1373 cm1, and C-N stretch at 1 165 cm1. Table 7. Extraction attempts using a Soxhlet.

[0253] Example 9. Antimicrobial activity

[0254] LDPE-C66H133-DMBA, LDPE-C66H133-PYR, and LDPE-C66H133-CH were tested for antimicrobial activity. A total of six samples was prepared with two different loadings (2 and 4 wt%) for each of the antimicrobial additives. The first step involved growing E. coli bacteria on an agar plate. Then the microbial suspension was diluted using 1 .0 g of tryptone, the pancreatic digest of casein, 8.5 g NaCI and 1000 ml of water. To preserve the living bacteria during the counting process, a solution of 15.0 g tryptone, 5.0 g soya peptone, 5.0 g NaCI, 15.0 g agar, and 1000 ml of water was used. The surface of the sample and reference sample was first disinfected using ethanol and 1 mm thick sample with 1cm*1cm dimensions was used. 10 pL of the bacterial suspension with a known number of viable bacteria was exposed to the sample for 5 minutes. Subsequently, the viable bacteria were washed with a recovery solution containing 1 .0 g tryptone, 5.0 g of NaCI, 5.0 g of polysorbate, and 1000 ml of water. The final step involved counting the remaining living bacteria to determine the killing activity.

[0255] All six samples have shown killing efficiencies against E. coli bacteria with some variation in the degree of the viable bacteria remaining on the surface. Table 8 lists the percentages of bacteria remaining after 5 minutes of contact time with the LDPE / additive samples. LDPE-C66H133-DMBA showed the lowest killing efficiency among all six samples, with 88% for 4 wt% and 2 wt% loading. LDPE-C66H133-PYR exhibited the highest killing efficiency of 97% at both 4 wt% and 2 wt% loading. LDPE-CeeH I33-CH also showed excellent efficiency with 96% for 4 wt% and 2 wt% loading (Table 8 and Figure 1). Statistical significance calculations were applied to the obtained antimicrobial activity data with a p-value less than 0.001 . The close match in antimicrobial activities between 2 and 4 wt% loading indicates that the surface is saturated at 2 wt% and higher loading percentages are unlikely to have a substantial impact. Table 8. Antimicrobial efficiencies of various LDPE / PE-X blends against E.coli MC1000.

[0256] Conditions: Bacterial strain: E. coli M1000; 5 minutes contact time. The statistical analysis was performed with a two-tailed Student’s t test. The data are presented as the means ± SDs of two biological replicates and two replicates.

[0257] Since the PE additives contain alkyl chains of 66 carbons on average, the weight percentage of the actual active antimicrobial ingredients can be calculated. Figure 2 shows the molecular weight fraction of the active antimicrobial compound versus the alkyl chain for each additive. The actual loading percentage of the active material was calculated by considering the weight percentage of the additive into LDPE, the functionality percentage of the additive, and the weight fraction of the active ingredient in the additive (Table 9). Table 9 indicates that incorporating less than 1 wt% of the active antimicrobial agent into LDPE is sufficient to manufacture antimicrobial LDPE surfaces. For example, 0.3 wt% loading of pyridinium iodide is enough to show 97 % bacterial killing efficiency. Low loading percentages are crucial in antimicrobial packaging applications.

[0258] Table 9. Actual loading of the active antimicrobial compound (wt%). a) The weight fraction of the active antimicrobial compound in the PE additives was taken from Figure

[0259] 2. b) Functionality percentage of the additive was obtained using1H NMR. Actual loading of the active antimicrobial compound (wt%) = Additive loading (wt%) *

[0260] Functionality of the additive (%) Active antimicrobial compound weight fraction (wt.%) c) 100 100

[0261] Example 10. Activity of phosphonium-based additives

[0262] Phosphonium-based additives were synthesised as described in Example 3. The additives were then blended with LDPE and tested as discussed below.

[0263] Method of blending functionalized PE additives and LDPE

[0264] PE-PR3I polymers and LDPE were weighed according to the desired weight fraction, and then transferred to a 100 ml flask. 50 ml of dried toluene was added under stirring and the flask was gradually heated and kept at 120 °C for 10 minutes. The flask was cooled when all products had dissolved and the mixing was complete. The morphology of the product at this point looked like a gel. The product was precipitated in methanol, filtered and washed with methanol and dried in a vacuum oven at 60 °C overnight to give a white powder. The LDPE / PE-PnBu3l polymer blends were then hot-pressed into round discs of 4 cm diameter.

[0265] Antimicrobial testing of PE-PnBu3l

[0266] Anti-microbial performance tests have been performed using E. coli bacteria grown on agar plates and applied to various LDPE / PE-PnBu3l polymer squares of 1x1 cm. Three different additive loadings were used at 2, 4 and 10 wt% of PE-PnBu3l in LDPE and the viability of the E. coli bacteria after different exposure times of 3 minutes (Table 10) and 1 hour (Table 11) was determined. The testing results were compared with a control sample of pure LDPE, prepared and hot-pressed under the same conditions. The viability is expressed as a percentage relative to the control sample of pure LDPE, which was normalised at 100% viability.

[0267] Table 10. Viability after 3 minutes exposure time. Table 11 . Viability after 1 hour exposure time.

[0268] It will be appreciated that the above description is made by way of example and not a limitation of the scope of the appended claims, including any equivalents as included within the scope of the claims. Various modifications are possible and will be readily apparent to the skilled person in the art. Likewise, features of the described embodiments can be combined with any appropriate aspect described above and optional features of any one aspect can be combined with any other appropriate aspect.

Claims

CLAIMS1. A functionalised polyolefin of formula PO-X, wherein:PO is a polyolefin having a chain length of at least 20 carbon atoms; andX is a positively charged functional group or a functional group capable of forming a cation at pH 7.

2. The functionalised polyolefin of claim 1 , wherein PO is polyethylene (PE) or polypropylene (PP).

3. The functionalised polyolefin of claim 2, wherein PO is polyethylene (PE).

4. The functionalised polyolefin of any preceding claim, wherein X or the cation is selected from an ammonium cation, a phosphonium cation, a pyridinium cation, an imidazolium cation, an amidinium cation, and a guanidinium cation.

5. The functionalised polyolefin of claim 4, wherein X or the cation is selected from an ammonium cation, a pyridinium cation, and a guanidinium cation.

6. The functionalised polyolefin of any preceding claim, wherein X is selected from:

7. The functionalised polyolefin of any preceding claim, wherein PO has a chain length of 20 to 100 carbon atoms.

8. The functionalised polyolefin of claim 7, wherein PO has a chain length of 50 to 80 carbon atoms.

9. A process for preparing the functionalised polyolefin of any one of claims 1-8, the process comprising: reacting Zn(PO)2 with iodine to obtain PO-I; and reacting PO-I to obtain PO-X, wherein PO has a chain length of at least 20 carbon atoms.

10. The process of claim 9, wherein Zn(PO)2 is produced by polymerising an olefin in the presence of a zinc alkyl and a catalyst system.11 . The process of claim 9 or 10, wherein reacting PO-I to obtain PO-X comprises reacting PO-I with a tertiary amine.

12. The process of claim 9 or 10, wherein reacting PO-I to obtain PO-X comprises reacting PO-I with a pyridine.

13. The process of claim 9 or 10, wherein reacting PO-I to obtain PO-X comprises: reacting PO-I with an azide to obtain PO-N3; reducing the azide to obtain PO-NH2; and reacting PO-NH2 with a cyanoguanidine.

14. The process of claim 9 or 10, wherein reacting PO-I to obtain PO-X comprises: reacting PO-I with NH3 to obtain PO-NH2; and reacting PO-NH2 with a cyanoguanidine.

15. The process of claim 9 or 10, wherein reacting PO-I to obtain PO-X comprises reacting PO-I with a tertiary phosphine.

16. A functionalised polyolefin obtainable by the process of any one of claims 9-15.

17. A polyolefin blend comprising a first polyolefin and a second polyolefin, wherein the first polyolefin is a functionalised polyolefin as defined in any one of claims 1-8 or 16.

18. The polyolefin blend of claim 17, wherein the first polyolefin is provided at a loading of 0.01 wt% to 4 wt% relative to the total mass of the polyolefin blend.

19. The polyolefin blend of claim 18, wherein the first polyolefin is provided at a loading of 0.5 wt% to 2 wt% relative to the total mass of the polyolefin blend.

20. The polyolefin blend of any of claims 17-19, wherein the second polyolefin is selected from polyethylene (PE), polypropylene (PP), and mixtures thereof.21 . The polyolefin blend of any of claims 17-20, wherein PO is PE and the second polyolefin is PE.

22. A process for preparing the polyolefin blend of any one of claims 17-21 , the process comprising melt blending the first polyolefin with the second polyolefin.

23. Use of a functionalised polyolefin as defined in any one of claims 1-8 or 16 as an antimicrobial polymer additive.

24. A method for imparting antimicrobial properties to a surface, the method comprising applying a functionalised polyolefin as defined in any one of claims 1-8 or 16 or a polyolefin blend according to any one of claims 17-21 to the surface.

25. A surface or article comprising (i) a functionalised polyolefin as defined in any one of claims 1- 8 or 16 or (ii) a polyolefin blend according to any one of claims 17-21.

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