Polymer, packaging material and process for preparing polymer

Abstract

A polymer comprising repeating units comprising in the backbone an aromatic cyclic moiety, wherein a helical polymer structure is provided by pi-pi interactions between aromatic cyclic moieties, packaging comprising the polymer and process for preparing the polymer and the packaging. The polymer confers moisture and gas barrier properties on the packaging.

Description

[0001] POLYMER, PACKAGING MATERIAL AND PROCESS FOR PREPARING POLYMER

[0002] Field of the invention

[0003] The present invention concerns a polymer, packaging material and a process for preparing a polymer.

[0004] Background of the invention

[0005] Packaging of manufactured food products is a vital part of the food industry today as it ensures food safety, preserves food quality and plays an important role in production processes, in brand communication and in digitalization. Indeed, several studies show that for a large part of consumers the packaging of a product is one key aspect that drives the purchase decision.

[0006] Plastic packaging is used frequently in the economy and in people's daily lives. It has multiple advantages, such as its 3D shape flexibility, its light weight and its barrier properties. Such a weight reduction contributes to fuel saving and CO2 reduction during transport, for example. Its barrier properties help to reduce food waste due to a positive effect on increasing shelf life. The barrier properties also help to secure food safety.

[0007] To ensure that plastic waste is reduced, significant efforts are made in the industry and in commerce. Replacing plastics with paper or fibre-based solutions in food packaging is one way forward, but not an easy task. A change in packaging material must not compromise consumer safety or product quality, nor generate food waste. The packaging must serve to protect the food, but must also be robust enough to be handled by machines during the production process, and must allow that the food product is presented effectively.

[0008] There is a need in the art for materials that provide moisture and oxygen barrier properties.

[0009] Summary of the invention

[0010] The objective of the present invention is to improve the state of the art and, in particular, to provide new polymers for increased barriers to moisture and gasses; and to provide packaging materials comprising the new polymers and processes for preparing the new polymers. Consequently, the objectives of the present invention are achieved by the subject matter of the independent claims. The dependent claims further develop the concept of the present invention.

[0011] The present inventors propose to solve the above problems by providing a polymer having a backbone comprising repeating units containing an aromatic cyclic moiety, wherein a helical polymer structure is provided by pi-pi interactions between aromatic cyclic moieties.

[0012] The present invention further provides a packaging material comprising a polymer in accordance with the invention.

[0013] The present invention further provides a process for preparing polymers in accordance with the invention.

[0014] Detailed description of the invention

[0015] Definitions

[0016] As used in this specification, the words "comprises", "comprising", and similar words, are not to be interpreted in an exclusive or exhaustive sense. In other words, they are intended to mean "including, but not limited to".

[0017] Polymer

[0018] The present invention provides a polymer having a backbone comprising repeating units containing an aromatic cyclic moiety, wherein a helical polymer structure is provided by pi-pi interactions between aromatic cyclic moieties.

[0019] Several factors can contribute to a polymer's ability to act as a good water and gas vapor barrier. These include:

[0020] • Polymers with a high degree of crystallinity, low free volume, and high glass transition temperature (Tg) tend to have lower water vapor transmission rate (WVTR) values.

[0021] • Polymers with low polarity tend to have lower WVTR values due to the lack of attraction of the non-polar groups to water. The water molecules cannot pass easily through the matrix leading to higher barrier to water vapor. • Polymers with high molecular weight and low level of branching tend to have lower WVTR values due to their higher chain entanglement and reduced free volume.

[0022] • Crosslinking of polymer chains can reduce the free volume and increase the density of the polymer, resulting in a lower WVTR.

[0023] • The addition of barrier additives such as metal oxides, clays, or carbon nanotubes can improve the barrier properties of the polymer by reducing the free volume and increasing the tortuosity of the diffusion path for water vapor.

[0024] • Film thickness linearly influences diffusion and thus the WVTR due to the longer diffusion path for water vapor.

[0025] The inventors realised that polymers that contain aromatic rings in their backbone, such as isoquinoline linked to hydroxybenzoic acid or hydroxy picolinic acid by ester functions, and polymers of divinyl pyridine have the potential to exhibit a better water vapor barrier compared to conventional polymers. Without wishing to be bound by theory, the inventors propose that this is because the aromatic rings can interact through pi-pi stacking interactions, which can lead to the formation of a helical conformation. This helical conformation can confer a smaller polymer volume and higher stackability, which can reduce the free volume of the polymer and limit the diffusion of water molecules through it. The helical structures thus provide more stability than linear stacking structures in polymeric materials. The inventors realised that this is because the helical structure allows for greater packing efficiency and reduces the free volume of the polymer, which can increase its mechanical and thermal stability. Additionally, the aromatic rings confer hydrophobic properties to the polymer leading to a limited diffusion of water molecules through it.

[0026] In preferred embodiments, the polymer comprises repeating units comprising in the backbone an aromatic moiety selected from the group consisting of benzene, naphthalene, anthracene, pyridine, quinoline, isoquinoline, pyrazine, quinoxaline, acridine, pyrimidine, quinazoline, pyridazine, cinnoline, and phthalazine.

[0027] In preferred embodiments, the polymer comprises repeating units comprising in the backbone two aromatic moieties independently selected from the group consisting of benzene, naphthalene, anthracene, pyridine, quinoline, isoquinoline, pyrazine, quinoxaline, acridine, pyrimidine, quinazoline, pyridazine, cinnoline, and phthalazine. In preferred embodiments, the polymer backbone comprises repeating units of formula (I) wherein

[0028] 0, 1 or 2 of X1, X2, X3and X4are N,

[0029] 2, 3 or 4 of X1, X2, X3and X4are CR1,

[0030] 0, 1 or 2 of Y1, Y2, Y3, Y4, Y5and Y6are N,

[0031] 4, 5 or 6 of Y1, Y2, Y3, Y4, Y5and Y6are CR1,

[0032] L is selected from the group consisting of C(=O)O, OC(=O), NR1C(=O) and C(=O)NR1, M is selected from the group consisting of C(=O)O and OC(=O), each R1is independently selected from the group consisting of H and CH3.

[0033] In preferred embodiments, L is C(=O)O or C(=O)NR1.

[0034] In preferred embodiments, one of X1, X2, X3, X4, Y1, Y2, Y3, Y4, Y5and Y6is N and the rest are CR1. For instance, X1, X2, Y1or Y4is N.

[0035] In preferred embodiments, each R1is H.

[0036] In preferred embodiments, M is C(=O)O.

[0037] When L is NR1C(=O) or C(=O)NR1, the helical conformation can be stabilised and enhanced by hydrogen bonding of the amide groups with neighbouring hydroxyl groups conferring a smaller polymer volume and higher stackability. This may reduce the free volume of the polymer and limit the diffusion of water molecules through it.

[0038] In other embodiments, the polymer backbone comprises repeating units of formula (II) wherein

[0039] 0, 1 or 2 of X1, X2, X3and X4are N,

[0040] 2, 3 or 4 of X1, X2, X3and X4are CR2,

[0041] 0, 1 or 2 of Y1, Y2, Y3and Y4are N,

[0042] 2, 3 or 4 of Y1, Y2, Y3and Y4are CR2,

[0043] L2is an aliphatic hydrocarbon chain having length 2n+2, n is an integer from 0 to 4, each R2is independently selected from the group consisting of H, CH3, OR3and CH2OR3, and R3is H or Ci-C6alkyl.

[0044] In preferred embodiments, one of X1, X2, X3and X4and one of Y1, Y2, Y3and Y4are N and the rest are CR2. For instance, the polymers may be formed from divinyl pyridine monomers (DVP polymers).

[0045] In some embodiments, X1and Y1are the same, X2and Y2are the same, X3and Y3are the same, and X4and Y4are the same. In other embodiments, X1and Y1are different, X2and Y2are the same, X3and Y3are the same, and X4and Y4are the same.

[0046] In preferred embodiments, n is 0 or 1. L2is preferably CH2CH2or CH2CH2CH2CH2. When n is 0, L2is CH2CH2. When n is not 0, i.e. L is CH2CH2CH2CH2or longer, the flexible structure of the polymer allows freer adoption of different helical conformations giving rise to different WVTR properties. Polymers formed from divinyl pyridine monomers exhibit improved water vapor barrier properties due to their unique structure. DVP polymers can form helical structures due to the flexible ethylene backbone and the pi-stacking possibilities of the aromatic moieties, which can lead to a reduction in free volume and an increase in packing efficiency. This helical conformation can also lead to the formation of hydrogen bonds between the pyridine nitrogen and the carbonyl oxygen of adjacent monomers, further stabilizing the structure. The resulting polymer can have a higher glass transition temperature (Tg) and a lower WVTR compared to polymers that stack in a linear fashion. Additionally, the divinyl pyridine monomers confer hydrophobic properties to the polymer leading to a limited diffusion of water molecules through it.

[0047] In preferred embodiments, X1is CR2and R2is CH3. Otherwise, R2is preferably H.

[0048] In preferred embodiments, R3, when present, is H orCH3. In particularly preferred embodiments, R3, when present, is CH3.

[0049] Particularly preferred are polymers having a backbone comprising repeating units of any one of formulae

[0050] (1) to (10).

[0051]

[0052] The polymer according to the invention may be prepared as a homopolymer consisting of the repeating units disclosed herein, or as a copolymer comprising the repeating units disclosed herein and at least one additional repeating unit. When the polymer is provided as a copolymer, the polymer may comprise sections of polymer selected from the group consisting of ethylene acrylic and / or methacrylic acid copolymers, propylene acrylic acid copolymers, polyesters, polyolefins, polyvinylidene chloride (PVDC), polybutylene-succinate, thermoplastic starch, or a combination thereof. The copolymer may be provided as a block, random, alternate or graft copolymer.

[0053] The polymer defined herein is capable of being identified by reference to the repeating units in its backbone. A finished polymer in accordance with the present invention also has terminal groups. The terminal groups may be any suitable terminal groupcommonly found in polymers. In some embodiments, each terminal group is independently selected from the group consisting of R4, OR4, N(R4)2C(=O)OR4, OC(=O)R4, C(=O)NHR4, and NHC(=O)R4, wherein each R4is independently selected from the group consisting of H, C1-C12 alkyl (particularly methyl), C2-C12 alkenyl (particularly ethylenyl), and C2-C12 alkynyl.

[0054] In preferred embodiments of Formula (I), the terminal groups are independently selected from the group consisting of OR4, N(R4)2C(=O)OR4, OC(=O)R4, C(=O)NHR4, and NHC(=O)R4.

[0055] In preferred embodiments of Formula (II), the terminal groups are independently selected from the group consisting of C2-C6alkenyl, particularly ethylenyl.

[0056] Packaging material

[0057] The present invention provides a packaging material comprising a polymer according to the invention. In preferred embodiments, the packaging material is a film.

[0058] The polymer may be provided as a standalone film. The polymer may be incorporated into a composite packaging material, such as laminated films, foils and paper-based packaging materials.

[0059] In some embodiments, the polymer is a standalone film. The standalone film may have a thickness of 5 pm to 50 pm.

[0060] Composite packaging material, such as laminated films, foils and paper-based packaging materials may comprise the polymer according to the invention as an extruded or dispersed layer provided between other layers or as a coating. The polymer layer may have a grammage in the range of from about 1 gsm to about 30 gsm. The composite packaging material may include one or more of any of the following: an additional polymeric layer. For example, an additional polymeric layer may comprise a polymer selected from the group consisting of ethylene acrylic and / or methacrylic acid copolymers, propylene acrylic acid copolymers, polyesters, polyolefins, polyvinylidene chloride (PVDC), polybutylene-succinate, thermoplastic starch, ora combination thereof. The additional polymeric layer has a grammage in the range of from about 1 to about 100 gsm. a paper layer. For example, a paper layer may have a grammage in the range of from about 20 gsm to about 360 gsm, selected according to the application. an adhesive layer. For example, an adhesive layer may comprise a polymer selected from the group consisting of a latex / casein blend, starch, sugar derivatives, cellulose, amino resin, (poly)acrylate, polyvinyl alcohol (PVOH), ethylene vinyl alcohol (EVOH) polyvinyl acetate, polyacrylic acid, maleic acid-modified ethylene copolymers, methylcellulose, carboxymethylcellulose, carboxy-functional polyesters, polyethylene succinate, polybutylene succinate, ionomers or hydrophilic polyurethane, or a combination thereof. An adhesive layer may have a grammage in the range of from about 1 gsm to about 50 gsm a metallization layer. For example, a metallization layer may comprise any one selected from the group consisting of aluminium, aluminium oxide (AIOx) or silicon oxide (SiOx), or a combination thereof. A metallization layer may have a thickness in the range of from about 1 nm to about 500 nm. a polymeric film. For example, a polymeric film may comprise an oriented film. A polymeric film may comprise any one selected from the group consisting of oriented polypropylene (OPP), oriented polyester (OPET), oriented polyethylene (OPE), oriented polyamide (OPA) or oriented polylactic acid (OPLA), or a combination thereof. The polymeric film may have a grammage in the range of from about 1 gsm to about 100 gsm.

[0061] Without wishing to be bound by theory, the inventors believe that the unique helical polymer structure afforded by pi-pi stacking between the aromatic cyclic moieties will afford excellent moisture barrier (low WVTR) and gas barrier (low oxygen transmission rate - OTR) properties. Moreover, the aromatic nature of these polymers confers a hydrophobic character that affords moisture barrier properties. The packaging material prepared with the polymer according to the invention is thus expected to have a WVTR is below 2 (g • mm) / (m2• day) when measured at 25°C and 85 % Relative Humidity, more preferably below 1, below 0.5, below 0.1, or below 0.05 (g • mm) / (m2• day) .

[0062] Crucially, the packaging material provided with the polymer according to the invention is expected to have a WVTR that is 90% or less of the WVTR of a packaging material that is identical save for being prepared with polyethylene instead of the polymer according to the invention. Furthermore, a packaging material according to the present invention may preferably have a WVTR that is 80% or less, 70% or less, 60% or less, 50% or less, 40% or less, 30% or less, 20% or less, 10% or less, or even 5% or less of the WVTR of a packaging material that is identical save for being prepared with polyethylene instead of the polymer according to the invention.

[0063] The packaging material prepared with the polymer according to the invention is also expected to have an oxygen barrier transfer rate (OTR) is below 50 (cm3• mm) / (m2• day) when measured at 23°C and 50 % Relative Humidity and 20.95% oxygen concentration, more preferably below 45, below 40, below 30, below 25, below 10, below 1, or below 0.2 (cm3• mm) / (m2• day).

[0064] Crucially, the packaging material provided with the polymer according to the invention is expected to have a OTR that is 90% or less of the OTR of a packaging material that is identical save for being prepared with polyethylene instead of the polymer according to the invention. Furthermore, a packaging material according to the present invention may preferably have a OTR that is 80% or less, 70% or less, 60% or less, 50% or less, 40% or less, 30% or less, 20% or less, 10% or less, or even 5% or less of the OTR a packaging material that is identical save for being prepared with polyethylene instead of the polymer according to the invention.

[0065] Synthesis

[0066] A process for forming a polymer according to the invention comprises contacting a first reagent comprising an aromatic cyclic moiety with a second reagent comprising an aromatic moiety under conditions sufficient to form a polymer according to the invention. In preferred embodiments, the first reagent and the second reagent each comprise an aromatic moiety selected from the group consisting of benzene, naphthalene, anthracene, pyridine, quinoline, isoquinoline, pyrazine, quinoxaline, acridine, pyrimidine, quinazoline, pyridazine, cinnoline, and phthalazine.

[0067] For example, the first reagent may be a compound of formula (A) wherein

[0068] 0, 1 or 2 of X1, X2, X3and X4are N,

[0069] 2, 3 or 4 of X1, X2, X3and X4are CR1,

[0070] Q is OH or NH2, and each R1is independently selected from the group consisting of H and CH3.

[0071] The second reagent may be a compound of formula (B) wherein

[0072] 0, 1 or 2 of Y1, Y2, Y3, Y4, Y5and Y6are N,

[0073] 4, 5 or 6 of Y1, Y2, Y3, Y4, Y5and Y6are CR1,

[0074] T is OH or NH2, and each R1is independently selected from the group consisting of H and CH3.

[0075] In preferred embodiments, one of X1, X2, X3, X4, Y1, Y2, Y3, Y4, Y5and Y6is N and the rest are CR1. For instance, one of X1, X2, Y1or Y4is N.

[0076] In preferred embodiments, R1is H. In alternative embodiments, the first reagent and the second reagent each are a compound of formula (C) wherein

[0077] 0, 1 or 2 of X1, X2, X3and X4are N,

[0078] 2, 3 or 4 of X1, X2, X3and X4are CR2, n is an integer from 0 to 4, each R2is independently selected from the group consisting of H, CH3, OR3and CH2OR3, and

[0079] R3is H or Ci-C6alkyl.

[0080] In preferred embodiments, one of X1, X2, X3and X4is N and the rest are CR2. For instance, one of X2or X4is N.

[0081] In preferred embodiments, X1is CR2and R2is CH3.

[0082] In preferred embodiments, n is 0 or 1.

[0083] In preferred embodiments R2is H. In preferred embodiments, R3is H or CH3, preferably CH3.

[0084] The invention will now be illustrated by reference to the following non-limiting examples. Other arrangements are also envisaged within the scope of protection in accordance with the appended claims.

[0085] Example 1 - Isoquinoline esters of hydroxybenzoic acid or hydroxy picolinic acid

[0086] Isoquinoline esters of hydroxybenzoic acid or hydroxy picolinic acid can be synthesized using conventional esterification reactions, such as Fischer esterification using an acid catalyst or Steglich esterification using carbodiimide chemistry. Protection of the hydroxyl function of the hydroxybenzoic acid and the carboxylic acid of the isoquinoline moiety by a benzyl group can allow a selective coupling of both moieties. A subsequent deprotection affords the monomer that can then be reacted with itself using the Fischer esterification to form the polyester.

[0087] Example 2 - Isoquinoline esters of hydroxybenzoic acid or hydroxy picolinic acid

[0088] Isoquinoline amides of hydroxybenzoic acids or hydroxy picolinic acid can be synthesized using coupling reagents based on carbodiimide chemistry. Protection of the carboxylic acid of the isoquinoline amine and the hydroxy function of the hydroxybenzoic acid is required to have selective amide bond formation. A subsequent deprotection affords the monomer that can then be reacted with itself using the Fischer esterification to form the polyester.

[0089] Example 3 - Polymers of divinyl pyridine

[0090] Divinyl pyridine monomers can also be synthesised through olefin metathesis using ruthenium catalysts, such as Grubbs catalyst. This approach will afford the following structure:

[0091]

[0092] X4= CH and X3= N or X4= N and X3= CH

[0093] Y4= CH and Y3= N or Y4= N and Y3= CH

[0094] Example 4 - Moisture and oxygen barrier properties

[0095] Polymers comprising repeating units according to the invention were analysed computationally to evaluate their moisture barrier properties (WVTR) and oxygen barrier properties (OTR). The following values were obtained.

[0096] WVTR was evaluated at 23 °C and 85% relative humidity. OTR was evaluated at 23°C and 50 % Relative

[0097] Humidity and 20.95% oxygen concentration.

[0098] Embodiments

[0099] Various preferred features and embodiments of the present invention will now be described with reference to the following numbered paragraphs (paras).

[0100] 1. A polymer comprising repeating units comprising in the backbone an aromatic cyclic moiety, wherein a helical polymer structure is provided by pi-pi interactions between aromatic cyclic moieties.

[0101] 2. A polymer according to para 1, wherein the aromatic moiety is selected from the group consisting of benzene, naphthalene, anthracene, pyridine, quinoline, isoquinoline, pyrazine, quinoxaline, acridine, pyrimidine, quinazoline, pyridazine, cinnoline, and phthalazine.

[0102] 3. A polymer according to para 1 or para 2, wherein repeating units comprise two aromatic moieties in the backbone independently selected from the group consisting of benzene, naphthalene, anthracene, pyridine, quinoline, isoquinoline, pyrazine, quinoxaline, acridine, pyrimidine, quinazoline, pyridazine, cinnoline, and phthalazine.

[0103] 4. A polymer comprising repeating units of formula (I) wherein 0, 1 or 2 of X1, X2, X3and X4are N,

[0104] 2, 3 or 4 of X1, X2, X3and X4are CR1,

[0105] 0, 1 or 2 of Y1, Y2, Y3, Y4, Y5and Y6are N,

[0106] 4. 5 or 6 of Y1, Y2, Y3, Y4, Y5and Y6are CR1,

[0107] L is selected from the group consisting of C(=O)O, OC(=O), NR1C(=O) and C(=O)NR1,

[0108] M is selected from the group consisting of C(=O)O and OC(=O), and each R1is independently selected from the group consisting of H and CH3.

[0109] 5. A polymer according to para 4, wherein L is C(=O)O or C(=O)NR1.

[0110] 6. A polymer according to para 4 or para 5, wherein one of X1, X2, X3, X4, Y1, Y2, Y3, Y4, Y5and Y6is N and the rest are CR1.

[0111] 7. A polymer according to any of paras 4 to 6, wherein one of X1, X2, Y1or Y4is N.

[0112] 8. A polymer according to any of paras 4 to 7, wherein R1is H.

[0113] 9. A polymer according to any of paras 4 to 8, wherein M is C(=O)O.

[0114] 10. A polymer comprising repeating units of formula (II) wherein

[0115] 0, 1 or 2 of X1, X2, X3and X4are N,2, 3 or 4 of X1, X2, X3and X4are CR2,

[0116] 0, 1 or 2 of Y1, Y2, Y3and Y4are N,

[0117] 2, 3 or 4 of Y1, Y2, Y3and Y4are CR2, L2is an aliphatic hydrocarbon chain having length 2n+2, n is an integer from 0 to 4, each R2is independently selected from the group consisting of H, CH3, OR3and CH2OR3, and R3is H or Ci-C6alkyl.

[0118] 11. A polymer according to para 10, wherein one of X1, X2, X3and X4and one of Y1, Y2, Y3and Y4are N and the rest are CR2.

[0119] 12. A polymer according to para 10 or 11, wherein one of X2and X4is N and one of Y2and Y4is N.

[0120] 13. A polymer according to any of paras 10 to 12, wherein X1and one of Y1and Y2are CR2and R2is CH3.

[0121] 14. A polymer according to any of paras 10 to 13, wherein R2is H.

[0122] 15. A polymer comprising repeating units of any one of formulae (1) to (10).

[0123] 16. A packaging material comprising a polymer according to any of paras 1 to 15, preferably wherein the packaging material is a film.

[0124] 17. A packaging material according to para 16, wherein the moisture barrier transfer rate (WVTR) is below 2 (g • mm) / (m2• day) when measured at 25°C and 85 % Relative Humidity. 18. A packaging material according to para 16 or para 17, wherein the moisture barrier transfer rate (WVTR) is 90% or less of the moisture barrier transfer rate (WVTR) of an equivalent packaging material comprising polyethylene instead of the polymer according to any of claims 1 to 15.

[0125] 19. A packaging material according to any of paras 16 to 18, wherein the oxygen barrier transfer rate (OTR) is below 50 (cm3• mm) / (m2• day) when measured at 23°C and 50 % Relative Humidity and 20.95% oxygen concentration.

[0126] 20. A packaging material according to any of paras 16 to 19, wherein the oxygen barrier transfer rate (OTR) is 90% or less of the oxygen barrier transfer rate (OTR) of an equivalent packaging material comprising polyethylene instead of the polymer according to any of claims 1 to 15.

[0127] 21. A process for forming a polymer, wherein the process comprises contacting a first reagent comprising an aromatic cyclic moiety with a second reagent comprising an aromatic moiety under conditions sufficient to form a polymer according to any of paras 1 to 15.

[0128] 22. A process according to para 21, wherein the first reagent and the second reagent each comprise an aromatic moiety selected from the group consisting of benzene, naphthalene, anthracene, pyridine, quinoline, isoquinoline, pyrazine, quinoxaline, acridine, pyrimidine, quinazoline, pyridazine, cinnoline, and phthalazine.

[0129] 23. A process according to para 21 or para 22, wherein the first reagent is a compound of formula (A) wherein

[0130] 0, 1 or 2 of X1, X2, X3and X4are N,

[0131] 2, 3 or 4 of X1, X2, X3and X4are CR1,

[0132] Q is OH or NH2, and each R1is independently selected from the group consisting of H and CH3. 24. A polymer according to para 23, wherein R1is H.

[0133] 25. A process according to any of paras 21 to 24, wherein the second reagent is a compound of formula (B) wherein

[0134] 0, 1 or 2 of Y1, Y2, Y3, Y4, Y5and Y6are N,

[0135] 4, 5 or 6 of Y1, Y2, Y3, Y4, Y5and Y6are CR1,

[0136] T is OH or NH2, and each R1is independently selected from the group consisting of H and CH3.

[0137] 26 A polymer according to para 25, wherein one of X1, X2, X3, X4, Y1, Y2, Y3, Y4, Y5and Y6is N and the rest are CR1.

[0138] 27. A polymer according to para 25 or 26, wherein one of X1, X2, Y1or Y4is N.

[0139] 28. A process according to para 21 or para 22, wherein the first reagent and the second reagent each are a compound of formula (C) wherein

[0140] 0, 1 or 2 of X1, X2, X3and X4are N,

[0141] 2, 3 or 4 of X1, X2, X3and X4are CR2, n is an integer from 1 to 4, each R2is independently selected from the group consisting of H, CH3, OR3and CH2OR3, and R3is H or Ci-C6alkyl.

[0142] 29. A process according to para 28, wherein one of X1, X2, X3and X4is N and the rest are CR2.

[0143] 30. A polymer according to para 28 or 29, wherein one of X2or X4is N.

[0144] 31. A polymer according to any of paras 28 to 30, wherein X1is CR2and R2is CH3. 32. A polymer according to any of paras 28 to 31, wherein R2is H.

Claims

Claims1. A polymer comprising repeating units comprising in the backbone an aromatic cyclic moiety, wherein a helical polymer structure is provided by pi-pi interactions between aromatic cyclic moieties.

2. A polymer according to claim 1, wherein the aromatic moiety is selected from the group consisting of benzene, naphthalene, anthracene, pyridine, quinoline, isoquinoline, pyrazine, quinoxaline, acridine, pyrimidine, quinazoline, pyridazine, cinnoline, and phthalazine.

3. A polymer according to claim 1 or claim 2, wherein repeating units contain two aromatic moieties in the backbone independently selected from the group consisting of benzene, naphthalene, anthracene, pyridine, quinoline, isoquinoline, pyrazine, quinoxaline, acridine, pyrimidine, quinazoline, pyridazine, cinnoline, and phthalazine.

4. A polymer according to any of claims 1 to 3, comprising repeating units of formula (I)wherein0, 1 or 2 of X1, X2, X3and X4are N,2, 3 or 4 of X1, X2, X3and X4are CR1,0, 1 or 2 of Y1, Y2, Y3, Y4, Y5and Y6are N,4, 5 or 6 of Y1, Y2, Y3, Y4, Y5and Y6are CR1,L is selected from the group consisting of C(=O)O, OC(=O), NR1C(=O) and C^OJNR1,M is selected from the group consisting of C(=O)O and OC(=O), each R1is independently selected from the group consisting of H and CH3.

5. A polymer according to any of claims 1 to 3, comprising repeating units of formula (II)0, 1 or 2 of X1, X2, X3and X4are N,2, 3 or 4 of X1, X2, X3and X4are CR2,0, 1 or 2 of Y1, Y2, Y3and Y4are N,2, 3 or 4 of Y1, Y2, Y3and Y4are CR2,L2is an aliphatic hydrocarbon chain having length 2n+2, n is an integer from 0 to 4, each R2is independently selected from the group consisting of H, CH3, OR3and CH2OR3, and R3is H or Ci-C6alkyl.

6. A polymer according to any of claims 1 to 5, comprising repeating units of any one of formulae (1) to (10).

7. A packaging material comprising a polymer according to any of claims 1 to 6.

8. A packaging material according to claim 7, wherein the moisture barrier transfer rate (WVTR) is below 2 (g • mm) / (m2• day) when measured at 23°C and 85 % Relative Humidity.

9. A packaging material according to claim 7 or claim 8, wherein the moisture barrier transfer rate (WVTR) is 90% or less of the moisture barrier transfer rate (WVTR) of an equivalent packaging material comprising polyethylene instead of the polymer according to any of claims 1 to 8.

10. A packaging material according to any of claims 7 to 9, wherein the oxygen barrier transfer rate (OTR) is below 50 (cm3• mm) / (m2• day) when measured at 23°C and 50 % Relative Humidity and 20.95% oxygen concentration.

11. A packaging material according to any of claims 7 to 10, wherein the oxygen barrier transfer rate (OTR) is 90% or less of the oxygen barrier transfer rate (OTR) of an equivalent packaging material comprising polyethylene instead of the polymer according to any of claims 1 to 8.

12. A process for forming a polymer, wherein the process comprises contacting a first reagent comprising an aromatic cyclic moiety with a second reagent comprising an aromatic moiety under conditions sufficient to form a polymer according to any of claims 1 to 8.

13. A process according to claim 12, wherein the first reagent and the second reagent each comprise an aromatic moiety selected from the group consisting of benzene, naphthalene, anthracene, pyridine, quinoline, isoquinoline, pyrazine, quinoxaline, acridine, pyrimidine, quinazoline, pyridazine, cinnoline, and phthalazine.

14. A process according to claim 12 or claim 13, wherein the first reagent is a compound of formula (III)wherein l or 2 of X1, X2, X3and X4are N,2 or 3 of X1, X2, X3and X4are CR1,Q is OH or NH2, and each R1is independently selected from the group consisting of H and CH3; and wherein the second reagent is a compound of formula (B)wherein0, 1 or 2 of Y1, Y2, Y3, Y4, Y5and Y6are N,4, 5 or 6 of Y1, Y2, Y3, Y4, Y5and Y6are CR1,T is OH or NH2, and each R1is independently selected from the group consisting of H and CH3.

15. A process according to claim 12 or claim 13, wherein the first reagent and the second reagent each are a compound of formula (C)l or 2 of X1, X2, X3and X4are N,2 or 3 of X1, X2, X3and X4are CR2, n is an integer from 0 to 4, each R2is independently selected from the group consisting of H, CH3, OR3and CH2OR3, and R3is H or Ci-C6alkyl.

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