WO2026008409A1

WO2026008409A1 - Methods of preparing polymers using co2

Info

Publication number: WO2026008409A1
Application number: PCT/EP2025/067854
Authority: WO
Inventors: Daniel Stewart; Robert Raja; Panashe MHEMBERE
Original assignee: Viridico2 Ltd; University of Southampton
Current assignee: Viridico2 Ltd; University of Southampton
Priority date: 2024-07-01
Filing date: 2025-06-25
Publication date: 2026-01-08
Anticipated expiration: 2027-01-01
Also published as: GB2642304A; GB202409469D0

Abstract

The present invention relates to methods of forming polymers that lead to the incorporation of CO₂ into the polymer backbone. Due to the incorporation of hydrophobic end groups, the method can be used to produce high value surfactant-like end products while employing favourable reaction conditions, and avoiding the use of petrochemical feedstocks.

Description

Methods of Preparing Polymers Using CO2

Technical Field

The present invention relates to methods of forming polymers that lead to the incorporation of CO2 into the polymer backbone. By incorporating hydrophobic end groups, the method can be used to produce high value surfactant-like end products while employing favourable reaction conditions, and avoiding the use of petrochemical feedstocks.

Background

Finding "green" or environmentally favourable alternatives to unsustainable chemical compounds is a popular area of research in the chemical industry due to concerns regarding the poor environmental health of the planet.

Another major issue facing the world's environment, and one which has received much attention in recent years, is that of the release of CO2 into the atmosphere, driving climate change. Among solutions to curb this negative impact on the planet is that of recycling or capturing this CO2 before it is emitted into the atmosphere in a bid to decrease these CO2 emissions.

CO2 has utility in many reactions, for example its reduction into small molecules (carbon monoxide and methane) which can then be used for the synthesis of hydrocarbon fuels.

Research is underway into using CO2 for polymer formation, by way of heterogeneous and homogeneous catalytic polymerisation. Copolymerisation of CO2 and epoxides to furnish poly(alkylene)carbonates, is widely documented via a ring-opening copolymerisation reaction using a catalyst. Common catalysts used for this reaction include heterogeneous catalysts for example zinc catalysts and double metal cyanides, and homogeneous catalysts such as metal porphyrin complexes and metal catalysts based on salen ligands. The use of these catalysts however can often require unfavourable reaction conditions, such as high energy requirements. Considering heterogeneous catalysts, examples of recoverable, easily separated systems, with high polycarbonate selectivity have been limited to double metal cyanide (DMC) complexes and zinc glutarates (ZnGAs). For example, US4943677A, US4981948A and US5026676A all describe the synthesis of zinc glutarate catalysts which are used for the copolymerisation reaction between CO2 and epoxides to form poly(alkylene carbonates).

Similarly, Zhu, Q. et al., Polym. Int. 2002, 51 (10), 1079-1085; Eberhardt, R. et al., Macromol. Chem. Phys. 2004, 205 (1), 42-47; and Marbach, J.; et al., Catal. Sci. Technol. 2017, 7 (13), 2897-2905, Ree, M. et al., J. Polym. Sci. Part Polym. Chem. 1999, 37 (12), 1863-1876; and Ree, M. et al., Catal. Today 2006, 115 (1), 134-145 all describe the synthesis of zinc glutarate catalysts which are used for the copolymerisation reaction between CO2 and epoxides to form poly(alkylene carbonates).

Zinc glutarate catalysts suffer from a number of disadvantages: they require high pressures (typically 4-5 MPa CO2), relatively high temperatures (typically 60-100°C), high metal loadings (typically 30 wt% Zn) which typically increase the cost, and long reaction times (typically 40 hours), in order to obtain desirable polymer yields.

US4500704A, US4826953A, and CA1262597A, describe the synthesis of double metal cyanide catalysts which are used for the copolymerisation reaction between CO2 and epoxides to form poly(alkylene carbonates). Similarly, Meng, Q. et al., J. CO2 Util. 2016, 16, 86-96, describes the synthesis of a composite double metal cyanide/zinc glutarate catalyst which is used for the copolymerisation reaction between CO2 and epoxides to form poly(alkylene carbonates). However, double metal cyanides have very poor ability to insert CO2 into a polymer (typically 10-56 % CO2 insertion based on the literature). Therefore, when used to catalyse this copolymerisation reaction, the majority product tends to be polyether, not polycarbonate.

WO2021/123761 Al discloses methods for forming polymers in which CO2 is incorporated into the structure of the polymer.

Polymers with hydrophobic end groups are desirable for use in a wide variety of technical applications, due to their surfactant-like properties. These surfactant-like compounds can be used in detergents and lubricants, as well as additives such as dispersing agents, suspending agents, thickeners, coagulants, humectants, rheology modifiers, emulsifiers, fabric softeners, foaming and anti-foaming agents, soaps, adhesives etc. Due to their surfactant-like properties, polymers with hydrophobic end groups may replace typical surfactant and surfactant-like chemicals used in industry, for example as ingredients for the formulation of personal care products or industrial and household cleaning products.

Present methods for preparing polymers with hydrophobic end groups suffer from a number of disadvantages. These include, for example, reliance on the use of petrochemical feedstocks for raw materials and high energy consuming synthetic conditions such as high reaction temperatures and/or pressures, and/or lengthy reaction times. A further disadvantage associated with conventional methods for preparing polymers with hydrophobic end groups is that large volumes of organic solvents can be required. As many organic solvents release volatile organic compounds (VOCs), their use leads to an adverse effect on the environment. A further disadvantage can be low levels of CO2 incorporation.

It would be advantageous to provide a method for forming alternative high-value polymers such as surfactants, and surfactant- 1 ike chemicals that are not derived from petrochemical feedstocks. It would also be useful to provide a method for forming these polymers that does not require the use of Zn or cyanide-based catalysts, due to the disadvantages outlined above. It would be useful to provide a method of forming these polymers that has reduced reaction times. It would be useful to provide a method for forming these polymers that allows CO2 to be incorporated into the polymer.

It is an aim of the invention to obviate or mitigate one or more of the disadvantages associated with the prior art. It is also an aim of this invention to provide polymers with hydrophobic end groups that can reduce the dependence on polymers derived from petrochemical feedstocks.

It is an aim of this invention to provide a technology that can transform CO2 into high-value chemical products and intermediates, such as surfactant- 1 ike compounds, that are capable of replacing traditionally used petrochemically derived compounds. It is an aim of this invention to provide environmentally favourable polypropylene carbonate and polyethylene carbonate derived chemical intermediates and products than can replace traditional petrochemical based derivatives, such as surfactants and surfactant-like compounds. Furthermore, it is also an aim of this invention to utilise CO2 in the synthesis of these compounds, leading to its incorporation into the surfactant structure; this lends an environmentally favourable synthetic profile compared with traditionally used compounds. A route to such compounds which not only tackles the problem of sourcing desirable formulation ingredients to reduce or eliminate reliance on petrochemical feedstocks, but also has an environmentally favourable synthetic profile, is attractive.

It is also an aim of this invention to provide more environmentally favourable methods of producing high-value chemical products and intermediates based on CO2. By way of using more favourable reaction conditions, manufacturing energy requirements can be reduced in comparison to traditional methods. It is an aim of this invention to provide a method with more favourable reaction conditions. For instance, it is an aim of this invention to reduce energy requirements; and/or to reduce reaction temperatures; an/or to reduce reaction pressures; and/or to reduce reaction lengths; or any combination thereof. It is also an aim of this invention to negate or reduce the use of toxic and environmentally damaging chemicals, such as VOCs and cyanide-based catalysts.

Summary of the Invention

According to a first aspect of the present invention, there is provided a method of forming a polymer in which CO2 is incorporated into the structure of the polymer, wherein the method comprises reacting: an epoxide selected from propylene oxide, ethylene oxide, or a combination thereof; an alcohol; and

CO₂; in the presence of a catalyst, wherein the catalyst is a composition comprising a bulk material; and at least one surface; the bulk material comprising ions of a metal M bonded to one another via linker groups; the surface comprising ions of a metal M' bonded to one another via linker groups; the metals M and M' being the same or different; the surface comprising at least one first site A and at least one second, different site B; the site A having a hydroxyl bonded thereto; said site B being a Lewis acid site; said site A being capable of interacting with the epoxide and alcohol and optionally binding CO2; said site B being capable of binding the epoxide and alcohol and said site B being capable of binding CO2 such that the bound CO2 can react with the epoxide and alcohol; wherein the distance d between the site A and site B is such that the epoxide and alcohol and the bound CO2 can polymerise on the surface to form the polymer product.

Suitable catalysts for use in the invention, as well as methods of their preparation, are described in detail in W02021/123701 Al and WO2021/123761 Al.

As a skilled person would appreciate, an alcohol can be generally defined as an organic compound containing one or more hydroxyl groups attached directly to carbon atoms. According to the invention, the alcohol is of the formula R¹OH, in which R¹ is a C4-C22 hydrocarbon chain.

The alcohol is a monoalcohol/monohydric alcohol, i.e. it has one hydroxyl group.

In an embodiment, R¹ is C8-C22 hydrocarbon chain.

In an embodiment, R¹ is C12-C18 hydrocarbon chain. The hydrocarbon chain may be straight chain or branched.

In an embodiment the hydrocarbon chain is a straight chain hydrocarbon chain.

Examples of alcohols comprising a straight chain hydrocarbon chain include butanol, 2- butanol, pentanol, hexanol, decanol, dodecanol, hexadecanol and docosanol.

In an embodiment, the hydrocarbon chain is unsubstituted.

Advantageously, linear hydrocarbon chains readily produce micelles which are critical for surfactant behaviour.

In an embodiment, the alcohol may be selected from the group consisting of 2-butanol; 1- octanol; 1-dodecanol; and 1-docosanol.

In an embodiment, the method is carried out at a temperature between 50°C to 100°C.

In an embodiment, the method is carried out at a temperature between 60°C and 90°C.

In an embodiment, the method is carried out at a temperature between 65°C and 85°C.

In an embodiment, the method is carried out for a length of between 3 and 12 hours.

In an embodiment, the method is carried out for a length of between 3 and 10 hours.

In an embodiment, the method is carried out for a length of between 3 and 8 hours.

In an embodiment, the method is carried out for a length of between 4 and 6 hours.

In an embodiment, the method is carried out at a pressure of CO2 between 0.01 and lOMPa .

In an embodiment, the method is carried out at a pressure of CO2 between 0.1 - 8 MPa. In an embodiment, the method is carried out at a pressure of CO2 between 0.2 and 4 MPa.

In an embodiment, the method is carried out at a temperature between 70°C to 100°C. In an embodiment, the method is carried out at a temperature between 80°C to 90°C. These temperature ranges may be particularly suitable for embodiments in which the epoxide is ethylene oxide. In an embodiment, the method may be carried out at a temperature of about 85°C.

In an embodiment, the reacting is carried out for between 4.5 and 8 hours. This reaction length may be particularly suitable for embodiments in which the epoxide is ethylene oxide.

In an embodiment, the method is carried out at a temperature between 50°C to 100°C. In an embodiment, the method is carried out at a temperature between 60°C to 90 °C. These temperature ranges may be particularly suitable for embodiments in which the epoxide is propylene oxide. In an embodiment, the method may be carried out at a temperature of about 65°C.

In an embodiment, the reaction is carried out for between 3 and 6 hours. This reaction length may be particularly suitable for embodiments in which the epoxide is propylene oxide.

The reaction lengths for the methods of the invention are particularly favourable when compared with prior art processes.

In an embodiment, the molar ratio of alcohol to epoxide (alcohokepoxide) is from: 1:1 to 1:75.

In an embodiment, the molar ratio of alcohol to epoxide (alcohokepoxide) is from 1:2 to 1:45.

In an embodiment, the molar ratio of alcohol to epoxide (alcohokepoxide) is from 1:3 to 1:30. This may be particularly suitable for embodiments in which the epoxide is ethylene oxide.

In an embodiment, the molar ratio of alcohol to epoxide (alcohokepoxide) is from 1:5 to 1:30.

This may be particularly suitable for embodiments in which the epoxide is propylene oxide. In an embodiment, the molar ratio of alcohol to epoxide to CO2 (alcohol:epoxide:CC>2) is from: 1:1:1 to 1:75:40.

In an embodiment, the molar ratio of alcohol to epoxide to CO2 (alcohol:epoxide:CC>2) is from 1:1:1 to 1:40:40.

In an embodiment, the molar ratio of alcohol to epoxide to CO2 (alcohol:epoxide:CC>2) is from 1:5:5 to 1:25:25. This may be particularly suitable for embodiments in which the epoxide is ethylene oxide.

In an embodiment, the molar ratio of alcohol to epoxide to CO2 (alcohol:epoxide:CC>2) is from 1:15:5 to 1:55:15. This may be particularly suitable for embodiments in which the epoxide is propylene oxide.

In an embodiment, the molar ratio of the catalyst to alcohol (catalyst:alcohol) is from: 1:40 to 1:3000.

In an embodiment, the molar ratio of the catalyst to alcohol (catalyst:alcohol) is from: 1:65 to 1:1200.

In an embodiment, the molar ratio of the catalyst to alcohol (catalyst:alcohol) is from: 1:100 to 1:500. This may be particularly suitable for embodiments in which the epoxide is ethylene oxide.

In an embodiment, the molar ratio of the catalyst to alcohol (catalyst:alcohol) is from: 1:50 to 1:300. This may be particularly suitable for embodiments in which the epoxide is propylene oxide.

In an embodiment, the reacting is carried out in the absence of a solvent.

In an embodiment of the invention, the metal ions M and M' of the catalyst are selected from Sc³⁺, Cr³⁺, Al³⁺ and Fe³⁺.

In an embodiment of the invention, the linker groups of the catalyst are of the structure T(R)x(R')y(H)z wherein: T is a multivalent organic moiety; R is a functional group capable of coordinating metal ions M and M'; R' is a functional group incapable of coordinating to metal ions M and M', the functional group being other than H; x is 2 to 6; y is 0 to 4; and z is a number sufficient to occupy the remaining valencies on T. T may be a cycloalkyl, heterocycloalkyl, aryl or heteroaryl ring. In an embodiment, R is CO2H.

In an embodiment, the distance d is between 0.3 and 1 nm.

In an embodiment, the distance d is between 0.3 and 0.8 nm.

Advantageously, when the distance d between the A site and the B site is between 0.3 and 1 nm, the proximity of the CO2 to the reaction starting materials (epoxide and alcohol) favours polymerisation, and a reduction in the formation of cyclic carbonates. The distance d can be measured by suitable methods such as X-ray crystallography, as discussed in more detail below.

In an embodiment, the catalyst composition has the general formula [Sc³O(OH)(BTC)2] where BTC is benzene-l,3,5-tricarboxylic acid.

Advantageously, the inventors have determined that the methods of the invention can be used to form surfactant-like polymers in which CO2 is incorporated into the structure of the polymer. An advantage of the present invention is that the method allows the size and nature of the end group to be easily modified and tailored towards the intended application. A range of polymers with a wide range of end groups are accessible using the method of the invention, by tuning the hydrophobic end group. For instance, when a polymer of higher hydrophobicity is desired, an alcohol of increased carbon chain length can be used as a reactant. Conversely, when a polymer of lower hydrophobicity is desired, an alcohol of decreased carbon chain length can be used as a reactant. In this way, access is provided to a wide range of polymers that can directly compete with petrochemically derived compounds.

A further advantage of the present invention is that the reaction requires less energy (i.e. lower temperature and/or lower pressure and/or shorter reaction time) in comparison to conventional methods. Furthermore, the method used for formation of these polymers is solventless, thereby further increasing the favourable environmental profile of the method. Brief Description of the Drawings

Embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings in which:

Figure l is a graph showing the GPC measured number average molecular weight (M_n) of PPC- PPE (poly(propylene) carbonate - poly(propylene) ether) copolymers synthesised according to the invention versus the calculated figures;

Figure 2 is a ⁴⁵Sc magic angle spinning (MAS) NMR spectrum of the catalyst composition prepared in Example 1.1;

Figure 3 illustrates the general structure of the bulk material and surface structure of a hybrid platform catalyst composition useful in the methods of the invention, wherein the metal ions M and M' (shown in the Figure as M) are linked by trivalent linkers and showing unoccupied Lewis acid sites B.

Detailed Description

The present invention relates to methods of forming polymers in which CO2 is incorporated into the structure of the polymer, the method comprising reacting an epoxide selected from propylene oxide, ethylene oxide or a combination thereof, with an alcohol and with CO2 in the presence of a catalyst. The epoxide is ethylene oxide; propylene oxide; or a combination thereof. In an embodiment, the epoxide is either ethylene oxide or propylene oxide.

The polymers formed by the method of the invention have surfactant- 1 ike properties, making them highly desirable as ingredients for use in a wide range of consumer products. The surfactant properties of the polymers can advantageously be adjusted for the intended application, by appropriate selection of the alcohol reactant. For instance, a polymer with increased hydrophobicity can be obtained by increasing the length of the hydrocarbon chain of the alcohol reactant. Conversely, decreasing the length of the hydrocarbon chain of the alcohol, can impart a lower degree of hydrophobicity on the resultant polymer.

The polymers formed may be used as replacements for the petrochemically-derived intermediates and products currently used in many applications, for example in the formulation of industrial, domestic, and personal care products. This method of the invention can therefore help reduce the dependence of the chemical industry on petrochemical feedstocks.

The process of the present invention advantageously provides a streamlined method for accessing a wide range of polymers with hydrophobic end groups. These types of compounds are direct competitors for traditional surfactants that have a wide range of use in many industries, from for example adhesives and sealants used in aviation construction to creams and toiletries used in personal care products.

Not only does the process of the invention provide environmentally friendly alternatives to petrochemically derived intermediates and products, but the process of formation is also itself environmentally favourable. The process of the invention requires less energy than traditional processes for forming the same type of chemicals, for example by using lower temperatures, and/or lower pressures and/or shorter reaction times. The process is also solventless, and avoids the release of volatile organic compounds (VOCs) into the atmosphere.

The invention provides a method of forming a polymer in which CO2 is incorporated into the structure of the polymer, wherein the method comprises reacting : an epoxide selected from propylene oxide, ethylene oxide, or a combination thereof; an alcohol; and

CO₂; in the presence of a catalyst, wherein the catalyst is a composition comprising a bulk material; and at least one surface; the bulk material comprising ions of a metal M bonded to one another via linker groups; the surface comprising ions of a metal M' bonded to one another via linker groups; the metals M and M' being the same or different; the surface comprising at least one first site A and at least one second, different site B; the site A having a hydroxyl group bonded thereto; said site B being a Lewis acid site; said site A being capable of interacting with the epoxide and alcohol and optionally binding CO2; said site B being capable of binding the epoxide and alcohol and said site B being capable of binding CO2 such that the bound CO2 can react with the epoxide and alcohol; wherein the distance d between the site A and site B is such that the epoxide and alcohol and the bound CO2 can polymerise on the surface to form the polymer product. The catalyst composition is described in detail in W02021/123701 Al and WO2021/123761 Al, along with methods of its preparation. The catalyst composition may be a crystallite composition. The composition used in the present invention may be in the form of individual, single crystals with control over crystallite size and particle morphology. The catalyst composition comprises a bulk material. Typically, the bulk material comprises ions of a metal M bonded to one another via linker groups, this forming a framework or scaffold.

As used herein, the term "crystallite" generally means a small single crystal (i.e., a small single solid material in which the crystal latice of the material is continuous and unbroken, with no grain boundaries). Single crystal materials should be contrasted with polycrystalline or agglomerate materials which comprise a collection of crystals adhered together.

The metal M may be any metal capable of forming ions to which a linker group may coordinate to form the bulk material. Examples of such metals include: transition metals, including first 15 row transition metals such as Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn; second row transition metals such as Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag and Cd; third row transition metals such as Hf, Ta, W, Re, Os, Ir, Pt, Au and Hg; lanthanides such as La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu; and p-block metals such as Al, Ga, Ge, In, Sn, TI, Pb and Bi. The metal may be Sc, Cr, Al, or Fe. In an embodiment, the metal is Sc.

The metal ions M which coordinate with the linker groups to form the bulk material may be the same or different. In one embodiment, the bulk material comprises ions of only one metal M. In another embodiment, the bulk material comprises ions of a mixture of more than one (preferably 2 to 4, more preferably 2 or 3, most preferably 2) different metals M.

In an embodiment, only one metal is used. The metal M may be Sc.

In an embodiment, two metals are used (M and M').

The main function of the hydroxyl group of the catalyst, positioned on the surface of the catalyst, is to interact with the epoxide (ethylene oxide, propylene oxide or a combination thereof) and the alcohol, with which CO2 is incorporated in the final product. In particular, as an epoxide is present, the -OH group of the catalyst, positioned on the surface of the catalyst composition facilitates ring opening of the epoxide group to enable it to react with CO2 on the surface of the catalyst. In addition, the site A is optionally capable of binding with CO2. The surface of the composition is provided with a sufficient number of hydroxyl groups in sufficient proximity to the B-sites on the surface to enhance the activity of the catalyst towards the polymerisation reactions. As a skilled person would appreciate, the -OH group of the catalyst, positioned on the surface of the catalyst composition, can facilitate ring-opening of the cyclic monomer, allowing the polymer chain to grow therefrom. In the catalyst composition, site B is a Lewis acidic site. In this specification "Lewis acid" takes its normal meaning in the art of an electron pair acceptor. Depending on the intended use of the composition, the Lewis acidic site B may be vacant (unoccupied) or may have a Lewis base bound thereto.

The site B is capable of binding the alcohol and the epoxide. The site B is capable of binding CO₂.

In an embodiment, the Lewis acidic site B is unoccupied. In this embodiment the metal ion is therefore coordinatively unsaturated. By "coordinatively unsaturated" it is meant that not all of the usual coordination sites of the metal ion are occupied. Typically, 1, 2 or 3, in one embodiment 1 or 2, in one embodiment 1 coordination site is unoccupied. Byway of example, in the particularly preferred case of the compounds having the general formula [SC3O(OH)(BTC)2], the Sc³⁺ ion having a site B on the surface is 5-coordinated rather than the usual 6.

In use, the function of the unoccupied Lewis acidic site B is to bind a CO2 molecule such that the bound CO2 molecule interacts with the growing polymer chain, to form a polymer in which the bound CO2 is incorporated in the structure of the polymer. The Lewis acid facilitates high availability of CO2 for activation and subsequent insertion into the polymer product. The presence of the unoccupied Lewis acidic site on the surface of the composition facilitates reaction of the bound CO2 with the ring-opened epoxide group on the surface of the catalyst.

Fig. 3 illustrates the general structure of the bulk material and surface structure of a composition for use in the methods of the invention. In this embodiment, the metal ions M and M' are linked by trivalent linkers. The surface metal ions (M') are labelled A and B to illustrate the difference between the sites. In this embodiment, the Lewis acid sites B are unoccupied. The distance d between the A and B sites is important, as explained in more detail below. When used for catalysis of a polymerisation reaction wherein CO2 is incorporated into the structure of the polymer the proportions of the repeating unit including C0₂ incorporation (e.g. a carbonate repeating unit) are much greater than the repeating unit lacking CO₂ incorporation (e.g. an ether repeating unit).

In the catalyst composition, the distance between sites A and B should be sufficiently close together to allow, in use, the bound CO₂ molecule to interact with the epoxide (ethylene oxide, propylene oxide, or a combination thereof) and alcohol, with which the CO₂ will be incorporated. Therefore, the distance (designated d in Fig. 3) between the metal atom at site A, carrying the hydroxyl group, and the metal atom at site B is such that the epoxide and alcohol, and the bound CO₂ can react together on the surface to form a polymer in which CO₂ is incorporated into the structure of the polymer. The distance d may vary depending on the nature of the epoxide and alcohol, the linker group, and the metal ions M' on the surface. In an embodiment, the distance d is between 0.3 and 1 nm. This distance may be measured by known techniques. For instance, the distance d may be determined based on crystallographic data by means of a suitable computational method. As is known to those skilled in the art, suitable crystallographic methods for obtaining the data include X-ray crystallography. One such suitable X-ray crystallographic method is powder diffraction (PDF) analysis. One specific method for carrying out PDF analysis is shown below. In this specific example, the PDF analysis was carried out on a Rigaku R-Axis 3-circle Spider goniometer equipped with a curved Fujifilm® image plate mounted at the window of a graphite monochromated sealed tube silver (Ag Kal/Ka2 = 0.56094 A) generator operating at 1.2 kW (40kV, 30mA). A borosilicate capillary of diameter 1 mm with a 0.01 mm wall thickness was used. A fixed capillary to detector distance of 127.4mm and an exposure time of 84 s per degree OJ of oscillation. An oscillation OJ of 84° was used, giving a total collection time of 117.6 minutes. The collected 2D powder pattern was integrated to a ID total scattering pattern using Rigaku 2DP software and transformed to a pair distribution function utilising GudrunX. This is described in more detail in Bi Hinge, S. J. L. Z. Fur Krist. - Cryst. Mater. 2004, 219 (3), 117-121, and in Egami, T. and Billinge, S. J. L. Underneath the Bragg Peaks: Structural Analysis of Complex Materials, Second edition; Pergamon Materials Series; Elsevier: Amsterdam, 2012.

Once the crystallographic data has been obtained, the distance d can be obtained from these data using a suitable computational method. One example of such a computational method uses density functional theory (DFT). As is known to the person skilled in the art, in the context of computational materials science, ab initio (from first principles) DFT calculations allow the prediction and calculation of material behaviour on the basis of quantum mechanical considerations, without requiring higher-order parameters such as fundamental material properties. In contemporary DFT techniques, the electronic structure is evaluated using a potential acting on the system's electrons. This DFT potential is constructed as the sum of external potentials V_ext, which is determined solely by the structure and the elemental composition of the system, and an effective potential V_eff, which represents interelectronic interactions. Thus, a problem for a representative supercell of a material with n electrons can be studied as a set of n one-electron Schrbdinger-like equations, which are also known as Kohn-Sham equations, as described, for example, in Hanaor, D. et al., Computational Mechanics. 2012 50 (2): 185-194.

By way of example, the interatomic distances may be calculated using a Gaussian 16 program at the density functional theory (DFT) level with the hybrid functionals B3LYP, as described in M. J. Frisch, et al., Gaussian 16 Rev. B.01, Wallingford, CT, 2016, and in A. D. Becke, J. Chem. Phys., 1993, 98, 5648-5652. For light atoms, the Dunning's correlated-consistent cc-pVDZ basis set may be used. Metal atoms may be described by effective core potentials and related basis set, as described in P. J. Hay and W. R. Wadt, J. Chem. Phys., 1985, 82, 299- 310. Dispersion energies were included in all the calculations with the atom-atom semiempirical method and parameters proposed by Grimme etal., J. Chem. Phys., 2010, 132, 154104. When computing coordination energies, Boys' counterpoise correction was applied to compensate the basis set superposition error (BSSE).

The catalyst composition for use in the method of the invention can be prepared by reacting a source of metal ions M and M' with a source of linker groups and a source of hydroxyl groups, and a modulator, and subjecting the composition to conditions such that the surface of the composition has first sites A to which the hydroxyl groups are bound, and second sites B which are Lewis acidic.

The source of metal ions M and M' may be any substance capable of producing the metals M and M' in the requisite ionic form. Typically, these comprise metal salts in which the metal is in ionic form with a suitable counter-ion, examples of which include halide (fluoride, chloride, bromide, iodide), hydroxide, alkoxide, sulfate, nitrate, phosphate, alkylsulfonate, arylsulfonate, alkylphosphonate, arylphosphonate (the alkyl and aryl parts of these counterions being as defined and exemplified above). The source of linker groups may be any substance capable of producing the linker groups in a form capable of coordinating to the metal ion. The source of linker groups comprises a compound which is a conjugate acid of the linker group as present in the final composition, such that the linker group which is coordinated to the metal ion is its conjugate base (i.e., it differs from the compound which is the source of the linker group by at least 1, preferably 1, 2, or 3, protons). Typically, the source of linker groups is an organic acid, such as a carboxylic acid. For instance, the source of linker groups may be a dicarboxylic acid. Alternatively, the source of linker groups may be a tricarboxylic acid. The source of linker groups may be benzene, 1,4-dicarboxylic acid or benzene-l,3,5-tricarboxylic acid.

The source of hydroxyl groups may be any compound capable of reacting so as to produce a composition wherein hydroxyl groups are present at the sites A on the surface of the composition. Examples of such sources include water.

A modulator may be added to the composition. As described in detail in WO2021/123761 Al, the addition of the modulator to the reaction mixture facilitates formation of compositions having the surface properties described herein which makes the compositions particularly active as catalysts, especially for catalysing reactions in which CO2 is incorporated into a molecular structure. Without wishing to be bound by theory, it is believed that the modulator binds to the metal salts used in the synthesis and competes with the linker during formation of the composition.

As used herein, the term "modulator" means a small organic molecule capable of binding to a metal ion. The modulator is a different organic molecule from the organic molecule which provides the source of linker groups. Typically, the modulator has a molecular weight of 30 to 900 Da. In one embodiment, the modulator has a molecular weight of 40 to 750 Da. In one embodiment, the modulator has a molecular weight of 50 to 600 Da. In one embodiment, the modulator has a molecular weight of 60 to 500 Da. In one embodiment, the modulator has a molecular weight of 70 to 400 Da. In one embodiment, the modulator has a molecular weight of 80 to 350 Da. In one embodiment, the modulator has a molecular weight of 90 to 300 Da. In one embodiment, the modulator has a molecular weight of 100 to 250 Da. In one embodiment, the modulator has a molecular weight of 60 to 180 Da. In one embodiment, the modulator has a molecular weight of 100 to 170 Da . In one embodiment, the modulator has a molecular weight of 110 to 200 Da. The metal ions M and M' may be the same and a modulator may be added to the composition. For instance, the metal ions M and M' may both be Sc³⁺ and a modulator is added to the composition during its preparation.

When preparing the catalyst composition, the stoichiometric ratio of the source of metal ions to the modulator may be between 1:0.001 and 1:1000, or between 1:0.1 and 1:500. The stoichiometric ratio of the source of metal ions to the modulator may be between 1:0.2 and 1:250, or between 1:0.4 and 1:150.

Typical modulators include organic acids (including but not limited to carboxylic acids, phosphonic acids, phosphoric acids, phosphinic acids, sulfonic acids, sulfinic acids, sulfenic acids), alcohols and amines.

The stoichiometric ratio of the modulator to the source of linker groups may be between 50:1 and 1:5. The stoichiometric ratio of the modulator to the source of linker groups may be between 20:1 and 1:2.

The stoichiometric ratio of the modulator to the source of linker groups may be between 15:1 and 5:1. The stoichiometric ratio of the modulator to the source of linker groups may be between 12:1 and 8:1. The stoichiometric ratio of the modulator to the source of linker groups may be between 11:1 and 9:1. The stoichiometric ratio of the modulator to the source of linker groups may be 10:1.

The stoichiometric ratio of the modulator to the source of linker groups may be between 2:1 and 1:2. The stoichiometric ratio of the modulator to the source of linker groups may be between 1.5:1 and 1:1.5. The stoichiometric ratio of the modulator to the source of linker groups may be between 1.2:1 and 1:1.2. The stoichiometric ratio of the modulator to the source of linker groups may be 1:1.

The source of linker groups may be benzene-l,3,5-tricarboxylic acid and the stoichiometric ratio of the modulator to benzene-l,3,5-tricarboxylic acid may be between 15:1 and 5:1. The source of linker groups may be benzene-l,3,5-tricarboxylic acid and the stoichiometric ratio of the modulator to benzene-1, 3, 5-tricarboxylic acid may be between 12:1 and 8:1. The source of linker groups may be benzene-1, 3, 5-tricarboxylic acid and the stoichiometric ratio of the modulator to benzene-1, 3, 5-tricarboxylic acid may be between 11:1 and 9:1. The source of linker groups may be benzene-l,3,5-tricarboxylic acid and the stoichiometric ratio of the modulator to benzene-l,3,5-tricarboxylic acid may be 10:1.

The source of linker groups may be benzene-l,3,5-tricarboxylic acid and the stoichiometric ratio of the modulator to benzene-l,3,5-tricarboxylic acid may be between 2:1 and 1:2. The source of linker groups may be benzene-l,3,5-tricarboxylic acid and the stoichiometric ratio of the modulator to benzene-l,3,5-tricarboxylic acid may be between 1.5:1 and 1:1.5. The source of linker groups may be benzene-l,3,5-tricarboxylic acid and the stoichiometric ratio of the modulator to benzene-l,3,5-tricarboxylic acid may be between 1.2:1 and 1:1.2. The source of linker groups may be benzene-l,3,5-tricarboxylic acid and the stoichiometric ratio of the modulator to benzene-l,3,5-tricarboxylic acid may be 1:1.

The source of linker groups may be benzene-l,3,5-tricarboxylic acid, the modulator may be benzoic acid and the stoichiometric ratio of benzoic acid to benzene-l,3,5-tricarboxylic acid may be between 15:1 and 5:1. The source of linker groups may be benzene-l,3,5-tricarboxylic acid and the modulator may be benzoic acid and the stoichiometric ratio of benzoic acid to benzene-l,3,5-tricarboxylic acid may be between 12:1 and 8:1. The source of linker groups may be benzene-l,3,5-tricarboxylic acid, the modulator may be benzoic acid and the stoichiometric ratio of benzoic acid to benzene-l,3,5-tricarboxylic acid may be between 11:1 and 9:1. The source of linker groups may be benzene-l,3,5-tricarboxylic acid the modulator may be benzoic acid and the stoichiometric ratio of benzoic acid to benzene-1,3,5- tricarboxylic acid may be 10:1.

The source of linker groups may be benzene-l,3,5-tricarboxylic acid, the modulator may be trichloroacetic acid and the stoichiometric ratio of trichloroacetic acid to benzene-1,3,5- tricarboxylic acid may be between 15:1 and 5:1. The source of linker groups may be benzene- 1,3,5-tricarboxylic acid, the modulator may be trichloroacetic acid and the stoichiometric ratio of trichloroacetic acid to benzene-l,3,5-tricarboxylic acid may be between 12:1 and 8:1. The source of linker groups may be benzene-l,3,5-tricarboxylic acid, the modulator may be trichloroacetic acid and the stoichiometric ratio of trichloroacetic acid to benzene-1,3,5- tricarboxylic acid may be between 11:1 and 9:1. The source of linker groups may be benzene- 1,3,5-tricarboxylic acid the modulator may be trichloroacetic acid and the stoichiometric ratio of trichloroacetic acid to benzene-l,3,5-tricarboxylic acid may be 10:1. The source of linker groups may be benzene-l,3,5-tricarboxylic acid and the stoichiometric ratio of the modulator to benzene-l,3,5-tricarboxylic acid may be between 2:1 and 1:2. The source of linker groups may be benzene-l,3,5-tricarboxylic acid and the stoichiometric ratio of the modulator to benzene-l,3,5-tricarboxylic acid may be between 1.5:1 and 1:1.5. The source of linker groups may be benzene-l,3,5-tricarboxylic acid and the stoichiometric ratio of the modulator to benzene-l,3,5-tricarboxylic acid may be between 1.2:1 and 1:1.2. The source of linker groups may be benzene-l,3,5-tricarboxylic acid and the stoichiometric ratio of the modulator to benzene-l,3,5-tricarboxylic acid may be 1:1.

The source of linker groups may be benzene-l,3,5-tricarboxylic acid, the modulator may be trifluoroacetic acid and the stoichiometric ratio of trifluoroacetic acid to benzene-1,3,5- tricarboxylic acid may be between 2:1 and 1:2. The source of linker groups may be benzene- 1,3,5-tricarboxylic acid, the modulator may be trifluoroacetic acid and the stoichiometric ratio of trifluoroacetic acid to benzene-l,3,5-tricarboxylic acid may be between 1.5:1 and 1:1.5. The source of linker groups may be benzene-l,3,5-tricarboxylic acid, the modulator may be trifluoroacetic acid and the stoichiometric ratio of trifluoroacetic acid to benzene-1,3,5- tricarboxylic acid may be between 1.2:1 and 1:1.2. The source of linker groups may be benzene-l,3,5-tricarboxylic acid, the modulator may be trifluoroacetic acid and the stoichiometric ratio of trifluoroacetic acid to benzene-l,3,5-tricarboxylic acid may be 1:1.

The source of linker groups may be benzene-l,3,5-tricarboxylic acid, the modulator may be trichloroacetic acid and the stoichiometric ratio of trichloroacetic acid to benzene-1,3,5- tricarboxylic acid may be between 2:1 and 1:2. The source of linker groups may be benzene- 1,3,5-tricarboxylic acid, the modulator may be trichloroacetic acid and the stoichiometric ratio of trichloroacetic acid to benzene-l,3,5-tricarboxylic acid may be between 1.5:1 and 1:1.5. The source of linker groups may be benzene-l,3,5-tricarboxylic acid, the modulator may be trichloroacetic acid and the stoichiometric ratio of trichloroacetic acid to benzene-1,3,5- tricarboxylic acid, may be between 1.2:1 and 1:1.2. The source of linker groups may be benzene-l,3,5-tricarboxylic acid, the modulator may be trichloroacetic acid and the stoichiometric ratio of trichloroacetic acid to benzene-l,3,5-tricarboxylic acid may be 1:1.

The stoichiometric ratio of the source of metal ions to the modulator may be between 1:0.1 and 1:500. The stoichiometric ratio of the source of metal ions to the modulator may be between 1:0.2 and 1:200. The method of preparing the catalyst composition may include the following sequential steps (a) and (b): (a) mixing the source of metal ions with the modulator; and (b) adding the linker to the mixture formed in step (a). Step (a) may be carried out with stirring. Step (b) may be carried out with stirring. The synthesis reaction may be carried out at elevated temperature, typically by heating the mixture formed in step (b). Typically, the reaction is carried out at a temperature between 50°C and 250°C. Preferably, the reaction is carried out at a temperature between 100°C and 200°C. More preferably, the reaction is carried out at a temperature between 130°C and 170°C.

The reaction time may be 12 to 120 hours. The reaction time may be 24 to 96 hours. The method may further comprise removing the modulator from the catalyst composition following its synthesis, typically by washing. Without wishing to be bound by theory, it is believed that removing the modulator by washing leaves behind a composition having multiple hydroxyl groups on the A sites of the surface of the composition. The washing may be carried out using any liquid capable of removing the modulator. Typical substances used include water, alcohols (typically alcohols having 1 to 4 carbon atoms) and mixtures thereof. A particularly preferred example is a mixture of ethanol and water.

An amount of the modulator may remain in the composition following its synthesis. For instance, a maximum of 10% of the modulator may remain in the composition following its synthesis. Alternatively, a maximum of 5%, 3%, 2% or 1% of the modulator remains in the composition following its synthesis. A maximum of 0.5% of the modulator may remain in the composition following its synthesis. A maximum of 0.3% of the modulator may remain in the composition following its synthesis. A maximum of 0.2% or a maximum of 0.1% of the modulator may remain in the composition following its synthesis. These percentages are calculated by weight based on the total weight of the composition.

The method of catalyst formation may be carried out in a solvent. Typical examples of suitable solvents include polar aprotic solvents, examples of which include N,N-dimethylformamide and dimethyl sulfoxide. The polar aprotic solvent may be present in a mixture with water. The solvent may be N,N-dimethylformamide. The stoichiometric ratio of the source of metal ions to the solvent may be between 1:10 and 1:200. Following reaction of the metal ion source and the linker source, the reaction mixture may be cooled to a temperature of less than 10°C, typically between -10°C and 10°C. This step is particularly preferred, as rapid cooling of the composition following the reaction results in a composition having particularly favourable surface properties. Typically, the cooling rate is from 2°C to 20°C per minute. The cooling rate may be from 5°C to 15°C per minute. The cooling rate may be from 8°C to 12°C per minute. The method may further comprise removal of water, so as to cause the sites B to become Lewis acidic.

Polymerisation method according to the present invention

As previously described, the invention relates to a method of forming a polymer in which CO2 in incorporated into the structure of the polymer, wherein the method comprises reacting: an epoxide selected from propylene oxide (PO), ethylene oxide (EO), or a combination thereof; an alcohol; and CO_2; in the presence of a catalyst, wherein the catalyst is as described in detail previously.

Scheme 1 illustrates generally the reaction of an alcohol (R¹OH) with propylene oxide in the presence of CO2 and a catalyst.

R’ = C4-C22 linear hydrocarbon chain

Scheme 1

The use of the catalyst (as illustrated generally in Fig. 3) in the polymer-forming reaction of the invention results in a polycarbonate polyether polymer having a greater proportion of carbonate units compared with ether units, and a low proportion of cyclic carbonate byproduct. In the process of the invention, the propylene oxide or ethylene oxide (or combination thereof), with which the CO2 reacts, comprises a ring structure, such that the ring opening reaction enables incorporation of the CO2 into the molecule. At least one repeating unit of the polymer formed contains a CO2 moiety and at least one repeating unit lacks the CO2 moiety forming a polycarbonate-polyether copolymer.

Polymer growth is initiated when an EO or PO moiety, or a combination of both EO and PO moieties, is inserted, by use of the catalyst, onto the hydroxy end of the alcohol, forming an ether linkage. Copolymerisation continues with CO2 to form a carbonate linkage, or an epoxide moiety which can form further ether linkages, and in this way the polymer chain grows. The ratio of ether to carbonate linkages can be modified through alteration of the reaction stoichiometry, CO2 pressure and reaction conditions. For instance, increased CO2 pressure leads to increased insertion of CO2 and consequential increased formation of carbonate linkages and lower insertion of the epoxide. Conversely, when CO2 pressure is lowered, there is an increase in insertion of the epoxide and consequential increase in ether linkages in the resultant polymer.

The polymer formed also contains the R¹ group of the alcohol reactant, which can be used to tailor the surfactant properties of the resultant polymer, for instance based on the intended application of the polymer. Variation in the length of the R¹ group within the hydrophobic moiety of the polymer leads to the ability to tune the Hydrophilic-Lipophilic balance (HLB) of the polymers, leading to different properties. For instance, a longer R¹ group can provide a lower HLB value, producing polymers that find use as anti-foaming agents and water-in-oil emulsifying agents. A shorter R¹ group can provide a higher HLB value, producing polymers that find use as solubilising agents, detergents and oil-in-water emulsifiers. In this way the polymer composition can be tailored to high value end products.

Various further features and aspects of the invention are defined in the claims.

The invention is now described in more detail below with reference to the following illustrative Examples. Examples

Example 1: Synthesis of catalyst compositions for use in the method of the invention

Example 1.1

Scandium nitrate hydrate (0.240 g) was dissolved into DMF (4 mL) and stirred vigorously at room temperature until dissolved. To the solution was added benzoic acid (0.550 g). The solution was stirred once again until homogeneous. To the solution was added benzene- 1, 3, 5-tricarboxylic acid (0.091 g) and DMF (4 mL). The solution was stirred until homogeneous. The resulting solution was sealed inside a 23 mLTeflon®-lined autoclave and heated in an oven at 150°C for 48 hours, after which the autoclaves were removed and rapidly cooled (at a rate of approximately 10°C per minute) to less than 10°C. The synthesised composition was filtered and washed with ethanol and water.

Example 1.2

Scandium nitrate (0.688 mmol) and chromium nitrate hexahydrate (0.172 mmol) were stirred in a 0.108 M solution of acetic acid in DMF (4 mL) at room temperature. Once homogenised, benzene-1, 3, 5-tricarboxylic acid (BTC, 0.430 mmol) in DMF was added and the solution was stirred further. The resulting solution was sealed inside a 23 mL Teflon®-lined autoclave and heated to 150 °C for 48 hours, after which autoclaves were removed from the oven and rapidly cooled (at a rate of approximately 10 °C per minute) to less than 10°C. The synthesised heterogeneous catalyst was collected by filtration and washed with deionized water, then ethanol.

The catalyst compositions prepared in Examples 1.1 and 1.2 were analysed by XRD, NMR, N2 adsorption, SEM and TEM, and the NMR results for Example 1.1 are shown in Figure 2.

Fig. 2 shows a ⁴⁵Sc magnetic angle spinning NMR spectrum confirming the presence of A and B sites on the surface of a catalyst composition for use in the methods of the invention. Magic Angle Spinning Nuclear Magnetic Resonance (MAS-NMR) measurements were collected at the UK 850 MHz Solid State NMR Facility on a wide bore 20.0 T Bruker A VANCE III spectrometer at the University of Warwick with a Neo Console, using a 4.0 mm HXY probe in doubleresonance mode. The sample was loaded into 4.0 mm zirconium oxide Bruker NMR rotors with vespel turbines under an N2 atmosphere. ⁴⁵Sc spectra (⁴⁵Sc Larmor frequency = 206.51 MHz) were referenced to a 1 mmol ScCh in D2O, using 192 scans and a pulse delay (dl) of 1 second. N2 was used for the drive, bearing and purge. Measurements were carried out with a 13.5 kHz spin-rate.

Example 2: Synthesis of polymers according to the method of the invention

2.1: Polymer synthesis from ethylene oxide (EQ) and 2-butanol

To the main reactor vessel was added 2-butanol (43 mL) and the catalyst (1.08 g) prepared according to Example 1.1. The reactor was sealed, evacuated, stirred at 200 rpm and heated to 85°C. To the reactor, CO2 was added via mass flow controller until a pressure of 0.8 MPa was achieved. The CO2 addition was stopped and EO was added portion-wise (21 g) to the reactor via mass flow controller from a pre-pressurised EO vessel, the pressure of which was controlled so to provide a 1 MPa differential between the pre-pressurisation vessel and the main reactor vessel. The rate of EO addition was controlled so to not exceed a total pressure of 0.9 MPa within the main reactor (typically between 45-100 grams/hour), and to maintain a reaction temperature of 85°C. Upon successful addition of one portion of EO to the main reactor the addition was ceased and the main reactor pressure was observed to drop rapidly before stabilising. The addition of CO2 and EO was replicated until the total quantity of EO (126 g) was added to the reactor. No further CO2 was added. The reaction was left to stir at 85°C for a total reaction time of 7.5 hours. Upon completion of the reaction, the main reactor was evacuated to vacuum and cooled to 30°C. Nitrogen was added to bring the vessel back to atmospheric pressure. The liquid polymer product was removed from the reactor and analysed via NMR spectroscopy and Gel Permeation Chromatography (GPC). The polymer product obtained exhibited the following: Mp (peak molecular weight) : 769; M_n: 831; M_w: 1614; PDI (D): 1.9 (The formula used to calculate PDI is M_w/M_n); and CO2 wt%: 30.38.

2.2: Polymer synthesis from ethylene oxide (EO) and 1-dodecanol

To the main reactor vessel was added 1-dodecanol (74.3 g) and the catalyst (1.08 g) prepared according to Example 1.1. The reactor was sealed, evacuated and heated to 85°C. To the reactor, CO2 was added via mass flow controller until a pressure of 0.8 MPa was achieved. The CO2 addition was stopped and EO was added portion-wise (21 g) to the reactor via mass flow controller from a pre-pressurised EO vessel, the pressure of which was controlled so to provide a 10-bar differential between the pre-pressurisation vessel and the main reactor vessel. The rate of EO addition was controlled so to not exceed a total pressure of 0.9 MPa within the main reactor (typically between 45-100 grams/hour), and to maintain a reaction temperature of 85°C. Upon successful addition of one portion of EO to the main reactor, the addition was ceased and the main reactor pressure was observed to drop rapidly before stabilising. The addition of CO2 and EO was replicated until the total quantity of EO (126 g) was added to the reactor. No further CO2 was added. The reaction was left to stir at 85°C for a total reaction time of 7.5 hours. Upon completion of the reaction, the main reactor was evacuated to vacuum and cooled to 30°C. Nitrogen was added to bring the vessel back to atmospheric pressure. The liquid polymer product was removed from the reactor and analysed via NMR spectroscopy and Gel Permeation Chromatography (GPC). The polymer product obtained exhibited the following: Mp: 511; M_n: 567; M_w: 1048; D: 1.9; and CO2 wt%: 31.34.

2.3: Polymer synthesis from propylene oxide (PO) and dodecanol

A 100 mL PTFE (polytetrafluoroethylene) reaction vessel was charged sequentially with dodecanol (5.51 g, 30 mmol, 1 equiv.), catalyst (80 mg) according to Example 1.1, and propylene oxide (12 mL, 178 mmol, 6 equiv.). The reaction vessel was fitted into a high- pressure reactor (Parr Micro 4590 100 mL, Illinois) and sealed. The reaction mixture was purged three times using CO2 (0.5 MPa), then heated to 65 °C before being pressurised with carbon dioxide (0.8 MPa). The mixture was left to stir for 6 hours under a continuous pressure of carbon dioxide (0.8 MPa), then cooled to room temperature and depressurised. The reaction vessel was removed and the resulting liquid was diluted with acetone and concentrated in vacuo to afford the crude residue, which was dissolved in the minimum amount of chloroform and precipitated dropwise into methanol. The suspension was centrifuged for 10 minutes at 800 RPM and the resulting liquid was concentrated in vacuo to afford the title compound as a clear liquid. GPC: Mp = 609; M_n = 708; Mw = 840; PDI = 1.19; CO₂ wt.% = 31%.

2.4: Polymer synthesis from ethylene oxide (EO) and 1-docosanol

To the main reactor vessel was added 1-docosanol (153 g) and the catalyst (1.08 g) according to Example 1.1. The reactor was sealed, evacuated and heated to 85°C. To the reactor, CO2 was added via mass flow controller until a pressure of 0.8 MPa was achieved. The CO2 addition was stopped and EO was added portion-wise (21 g) to the reactor via mass flow controller from a pre-pressurised EO vessel, the pressure of which was controlled so to provide a 1 MPa differential between the pre-pressurisation vessel and the main reactor vessel. The rate of EO addition was controlled so to not exceed a total pressure of 0.9 MPa within the main reactor (typically between 45-100 grams/hour), and to maintain a reaction temperature of 85°C. Upon successful addition of one portion of EO to the main reactor the addition was ceased and the main reactor pressure was observed to drop rapidly before stabilising. The addition of CO2 and EO was replicated until the total quantity of EO (126 g) was added to the reactor. No further CChwas added. The reaction was left to stir at 85°C for a total reaction time of 7.5 hours. Upon completion of the reaction, the main reactor was evacuated to vacuum and cooled to 30°C. Nitrogen was added to bring the vessel back to atmospheric pressure. The solid polymer product was dissolved so to enable removal from the reactor. The solvent was removed in vacuo and the resulting white, polymer product was analysed via NMR spectroscopy and Gel Permeation Chromatography (GPC). The polymer product obtained exhibited the following: Mp: 697; M_n: 880; M_w: 1345; D: 1.5; and CO2 wt%: 28.34.

Reaction yields: Up to and including 85% reaction yields were obtained for the above reactions.

As the skilled person would appreciate, the epoxide (i.e. ethylene oxide, propylene oxide or combination thereof,) can be added either sequentially or simultaneously with the alcohol, catalyst and CO2.

Example 3: Analysis of polymer properties

3.1: Effect of molar ratio of epoxide: alcohol on molecular weight

In order to demonstrate tailoring of the molecular weight of the polymer, the following study was conducted: a-butoxy-(jo-hydroxy-poly((propan-2-yl carbonate)-co-(propylene oxide)) (Polymer 1) was synthesised as outlined in Example 2.3 with the exception that the alcohol was 2-butanol, which was added at various molar ratios of epoxide:alcohol (See Table 1).

Polymer 1

The molecular weight of polymer 1 was controlled by the addition of 2-butanol at various molar ratios of epoxide:alcohol. Analysis was carried out on the polymers formed to obtain the average molecular weight values.

The number average molecular weight was measured by size exclusion chromatography, using the method outlined in in Shimadzu Gel Permeation Chromatography System - Application Data Book - (C190-0032, p. 81).

The values obtained for the repeating units ("n" and "m") were obtained using GPC analysis.

The results are shown in Table 1 below: number of repeating units (n+m) b: D (PDI polydispersity index) = M_w/M_n

M_p: peak molecular weight

Table 1: Effect of molar ratio of epoxide: alcohol on molecular weight

It can be seen from Table 1 that an increase in %PPC is obtained with an increase in epoxide relative to alcohol except for the highest amount of epoxide present relative to alcohol, where a slight decrease in %PPC is observed.

T1 3.2: Polymer synthesis using different alcohols (C4, Cs, C12 and C22)

In order to demonstrate tailoring of the polymer properties by way of using differing alcohol chain lengths, and the effect on the reaction, the following study was conducted:

Poly(propan-2-yl) carbonate-based polymers were synthesised as outlined in Example 2.3, with the exception that the starting alcohol was varied, and was used at various molar ratios of epoxide:alcohol, as shown in Table 2 below. The molecular weight was controlled by the addition of various alcohols (2-butanol, 1-octanol, 1-dodecanol, 1-docosanol) at molar various ratios of epoxide:alcohol as shown in Table 2. GPC analysis was carried out on the polymers formed to obtain the molecular weight values. It can be seen that the %PPC was highest for 1-octanol at a ratio of epoxide:alcohol of 6:1. For the same molar ratio of epoxide:alcohol (6:1) a lower %PPC is obtained using 1-dodecanol (70%) and 1-docosanol (72%). ^a: %PPC is the percentage of polypropylene carbonate) units (n) with respect to the total number of repeating units (n+m) ^b: D = M_w/Mn

Table 2: Effect of differing alcohols and molar ratio of epoxide:alcohol on molecular weight

It can be seen that the %PPC is highest using 1-octanol at a ratio of epoxide:alcohol of 6:1. For the same molar ratio of epoxide:alcohol (6:1) a lower %PPC is obtained using 1-dodecanol (70%) and 1-docosanol (72%). 3.3: Comparison of calculated and measured molecular weights

In order to compare calculated molecular weights with measured molecular weights, the following study was conducted:

Dodecanol-terminated poly(propan-2-yl) carbonate polymers were synthesised according to Example 2.3 with varying molecular weights; the molecular weight was controlled by the addition of 1-dodecanol at various molar ratios of epoxide:alcohol as shown in Table 3. GPC analysis was carried out on the polymers to obtain the molecular weight averages.

Table 3: Measured versus theoretical molecular weight

It can be seen that the measured molecular weights (measured by GPC) are similar to the theoretical molecular weight values. It can also be seen that the percentage of cyclic carbonate formation was lowest when the molar ratio of epoxide:alcohol was 10:1, and the highest percentage of cyclic carbonate formation was obtained with a ratio of epoxide:alcohol of 8:1.

3.4: PPC-PPE number average molecular weight - dodecanol-terminated polymers

A PPC-PPE (poly(propylene) carbonate - poly(propylene) ether) copolymer was synthesised according to Example 2.3 using varying amounts of dodecanol. Figure 1 shows a comparison graph of the number average molecular weight (M_n) of the PPC-PPE polymer synthesised according to the invention, and the calculated molecular weights for a PEC (poly(ethylene) carbonate) homopolymer, where m = 0. It can be seen from the graph that the measured and calculated values are similar and follow the same curve. 3.5: Tailoring of CO2 insertion by adjustment of reaction reagent ratios

Reactant ratios were calculated for both PPC and PEC polymers with varying number average molecular weight values for each of the alcohols C4, C12 and C22 , at target values of 100% and 25% PPC/PEC respectively. As the skilled person would appreciate, 100% PPC/PEC represents a high amount of carbonate linkages, and 25% PPC/PEC represents a low amount of carbonate linkages. Calculation data is presented in Tables 4 (PEC) and 5 (PPC) below.

Table 4: Ratios of reactants for varying alcohols and target PEC percentages

Table 5: Ratios of reactants for varying alcohols and target PPC percentages

As described previously, the properties of the polymers can be modified by adjusting the amount of reactant CO2. From Tables 4 and 5 it can be seen that in order to increase the PPC and PEC carbonate linkage formation, that an increase in the amount of CO2 is required; whereas, in comparison, to decrease the PPC and PEC carbonate linkage formation, a decrease in the amount of CO2 is required. Adjusting the ratios of the reactants in this way can be used to tailor the CO2 insertion and therefore consequently, the properties of the final polymer.

Alcohokepoxide: As can be seen from the tables 4 and 5 above, when a higher percentage value of PPC/PEC is targeted, i.e. 100%, the amount of epoxide should be decreased in relation to the amount of alcohol in comparison with when a lower percentage value of PPC /PEC is targeted, i.e. 25%, where the amount of epoxide should be increased, in relation to the amount of alcohol.

CO2:epoxide:alcohol: When a higher percentage of PPC/PEC is targeted, i.e. 100%, the ratio of CO2:epoxide is equal (i.e. 1:1). When a lower percentage value of PPC/PEC is targeted, i.e. 25%, the ratio of CO2:epoxide is different, with the amount of epoxide used in comparison to CO2 being in excess, at a ratio of approximately CO2:epoxide 1:4.

Catalyst:alcohol: When a higher percentage value of PPC/PEC is targeted, i.e. 100%, the amount of catalyst in relation to the alcohol is decreased in comparison to when a lower percentage of PPC/PEC is targeted, i.e. 25%, where the amount of catalyst in relation to the alcohol is increased.

Claims

1. A method of forming a polymer in which CO2 is incorporated into the structure of the polymer, the method comprising reacting: an epoxide selected from propylene oxide, ethylene oxide, or a combination thereof; an alcohol; and

CO_2; in the presence of a catalyst, wherein the catalyst is a composition comprising a bulk material; and at least one surface; the bulk material comprising ions of a metal M bonded to one another via linker groups; the surface comprising ions of a metal M' bonded to one another via linker groups; the metals M and M' being the same or different; the surface comprising at least one first site A and at least one second, different site B; the site A having a hydroxyl group bonded thereto; said site B being a Lewis acid site; said site A being capable of interacting with the epoxide and the alcohol and optionally binding CO2; said site B being capable of binding the epoxide and the alcohol and said site B being capable of binding CO2 such that the bound CO2 can react with the epoxide and the alcohol; wherein the distance d between the site A and site B is such that the epoxide and the alcohol and the bound CO2 can polymerise on the surface to form the polymer.

2. The method according to claim 1, wherein the alcohol is of formula R¹OH, in which R¹ is a C4 - C22 alkyl hydrocarbon chain.

3. The method according to claim 2 wherein R¹ is a Cs - C22 hydrocarbon chain.

4. The method according to claim 3 wherein R¹ is a C12 - Cis hydrocarbon chain.

5. The method according to any of claims 2 to 4, wherein the hydrocarbon chain is a linear hydrocarbon chain.

6. The method according to any preceding claim, wherein the reacting is carried out at a temperature of between 50°C to 100°C.

7. The method according to any preceding claim, wherein the reacting is carried out for between 3 hours and 10 hours.

8. The method according to any preceding claim, wherein the CO2 is introduced under pressure, wherein the pressure is between 0.01 and 10 MPa.

9. The method according to any preceding claim wherein the ratio of alcohol to epoxide (alcohokepoxide) is from 1:1 to 1:75.

10. The method according to claim 9 wherein the molar ratio of alcohol to epoxide (alcohokepoxide) is from 1:2 to 1:45.

11. The method according to any preceding claim wherein the molar ratio of alcohol to epoxide to CO2 (alcohol:epoxide:CO2) is from 1:1:1 to 1:75:40.

12. The method according to claim 11 wherein the molar ratio of alcohol to epoxide to CO2 (alcohol:epoxide:CO2) is from 1:1:1 to 1:40:40.

13. The method according to any preceding claim wherein the molar ratio of the catalyst to alcohol (catalyst:alcohol) is from 1:40 to 1:3000.

14. The method according to claim 13, wherein the molar ratio of catalyst to alcohol (catalyst:alcohol) is from 1:65 to 1:1200.

15. The method according to claim 1, wherein the metal ions M and M' are selected from Sc³⁺, Cr³⁺, Al³⁺ and Fe³⁺.

16. The method of any preceding claim, wherein the linker groups are of the structure T(R)x(R')y(H)z wherein: T is a multivalent organic moiety; R is a functional group capable of coordinating metal ions M and M'; R' is a functional group incapable of coordinating to metal ions M and M', the functional group being other than H; x is 2 to 6; y is 0 to 4; and z is a number sufficient to occupy the remaining valencies on T.

17. The method of any preceding claim, wherein T is a cycloalkyl, heterocycloalkyl, aryl or heteroaryl ring.

18. The method of any preceding claim, wherein in the catalyst composition, R is -CO2H.

19. The method of any preceding claim, wherein the distance d is between 0.3 and 1 nm.

20. The method of any preceding claim, wherein the catalyst composition has the general formula [Sc3O(OH)(BTC)2] where BTC is benzene-l,3,5-tricarboxylic acid.