Phenol compounds and (co)polymers thereof

The present invention relates to A phenol compound according to Formula (I): wherein: R1 is selected from the group consisting of, optionally substituted, 2-pyridyl, 3-pyridiyl and 4-pyridyl groups, wherein R1 is at position 2 or 3 of the phenol ring; R2 is selected from the group consisting of, optionally substituted, 2-pyridyl, 3-pyridiyl, 4-pyridyl and phenyl groups, wherein R2 is at position 5 or 6 of the phenol ring; and the phenol ring is optionally substituted at one or two positions, independently selected from positions 2, 3, 5 and 6, with a halogen atom or a with an optionally substituted C6-C12 aryl group or an optionally substituted C1-C10 alkyl group. The present invention relates also to (co)polymers comprising the phenol compound according to Formula (I) and membranes and ionic resins comprising said (co)polymers.

FIELD OF THE INVENTION

The present invention relates to novel monomers, (co)polymers prepared from these novel monomers, a process for the preparation of such (co)copolymers and the application of such polymers in membranes having a well-defined selectivity and an improved resistance to harsh environments.

BACKGROUND OF THE INVENTION

In the art, there is still a need for polymer membranes having a well-defined selectivity and an improved resistance to harsh environments. Many separation processes would benefit from the option of being performed at higher temperatures than is currently feasible with state-of-the-art polymer membranes. In particular, anion exchange materials which are often based on polyethylenimine or on trimethylammonium derivatives of polystyrene have limited thermo-oxidative stability.

Highly thermo-oxidatively stable Brønsted basic membranes, after complexation with a strong acid, are also of great potential value in polymer membrane fuel cells. Such higher operating temperatures may lead to simpler fuel cell stack design and allow the use of less pure hydrogen as well as other fuels compared to Nafion®-based fuel cells. Nafion® perfluorosulfonic acid ionomers have the general structure (Butler, G. B.; O'Driscoll, K. F.; Wilkes, G. L.JMS-Rev. Macromol. Chem. Phys.1994, C34(3), 325-373):

Another disadvantage of Nafion® membranes is that it requires 100% water saturation (i.e. a 100% RH environment) to achieve the required conductivity since water is the proton conducting phase. Hence, operation above 100° C. is virtually impossible due to the water loss from the Nafion® membranes, although an improved performance is expected at higher operating temperatures, e.g. a temperature in the range of about 120° C. up to about 150° C. Hybrid Nafion® membranes are also known in the art but have been applied without much success.

U.S. Pat. Nos. 5,525,436, 5,716,727 and 6,025,085 to R. F. Savinell and Morton H. Litt, incorporated by reference herein, disclose PBI (“PBI” means polybenzimidazole) and similar polymers doped with phosphoric acid. See also J-T Wang, J. S. Wainright, R. F. Savinell and M. H. Litt, J. Appl. Electrochem. 26, 751, 1996 and S. R. Samms, R. Wasmus and R. F. Savinell, J. Electrochem. Soc. 143, 1225, 1996. However, these systems have the disadvantage that they loose phosphoric acid during prolonged use which is presumably related to coagulation of the PBI by water from its phosphoric acid complex (cf. e.g. U.S. Pat. No. 7,045,241 to Akita Hiroshi and Komiya Teruaki, incorporated by reference herein, which discloses the isolation of a PBI composition by pouring its solution in polyphosphoric acid into water).

U.S. Pat. No. 6,723,757 to J. Kerres, A. Ullrich and T. Haring, incorporated by reference, discloses acid-base polymer blend membranes comprising as a first component either a cation exchanging polymer or an anion exchanging polymer and as a second component a polymer comprising one or more nitrogen containing basis moieties. However, pyridine as a nitrogen basic moiety is not disclosed.

US 2007/0141426 to S-w. Choi, H-y Sun, M-j Lee and W-s Jeon, incorporated by reference, discloses systems obtained by crosslinking polybenzimidazole with a benzoxazine-based monomer, wherein the nitrogen atom may be substituted with a 2-pyridyl or 3-pyridyl group.

There is, however, still a need in the art for improved polymer membranes.

SUMMARY OF THE INVENTION

The present invention relates to a phenol compound according to Formula (I):

wherein:R1is selected from the group consisting of, optionally substituted, 2-pyridyl, 3-pyridiyl and 4-pyridyl groups, wherein R1is at position 2 or 3 of the phenol ring;R2is selected from the group consisting of, optionally substituted, 2-pyridyl, 3-pyridiyl, 4-pyridyl and phenyl groups, wherein R2is at position 5 or 6 of the phenol ring; and
the phenol ring is optionally substituted at one or two positions, independently selected from positions 2, 3, 5 and 6, with a halogen atom or a with an optionally substituted C6-C12group or an optionally substituted C1-C10alkyl group.

The present invention also relates to (co)polymers made of the phenol compound according to Formula (I) and membranes and ionic resins comprising such (co)polymers.

DETAILED DESCRIPTION OF THE INVENTION

The verb “to comprise” as is used in this description and in the claims and its conjugations are used in its non-limiting sense to mean that items following the word are included, but items not specifically mentioned are not excluded. In addition, reference to an element by the indefinite article “a” or “an” does not exclude the possibility that more than one of the element are present, unless the context clearly requires that there is one and only one of the elements. The indefinite article “a” or “an” thus usually means “at least one”.

According to the present invention, suitable substituents for alkyl groups, aryl groups, phenyl groups and aryl groups include halogen atoms, in particular fluorine, chlorine and bromine atoms, and C1-C6alkyl groups, wherein the alkyl groups may be linear or branched.

According to the present invention, it is preferred that R2is selected from the group consisting of, optionally substituted, 2-pyridyl, 3-pyridiyl, 4-pyridyl groups. Suitable substituents include halogen atoms, in particular halogen atoms selected from the group consisting of fluorine, chlorine and bromine atoms, and optionally substituted C6-C12aryloxy groups. According to the present invention, it is preferred that R1and R2are an optionally substituted 3-pyridyl group.

It is also preferred that R1is at position 2 of the phenyl ring.

It is furthermore preferred that R2is at position 6 of the phenyl ring.

The present invention also relates to homopolymers or copolymers (further referred to as (co)polymers) which comprises a phenol compound according to the present invention. When the polymer is a copolymer, suitable comonomers include optionally substituted phenol monomers. Suitable substituents for such optionally substituted phenol monomers include halogen atoms, in particular halogen atoms selected from the group consisting of fluorine, chlorine and bromine atoms, optionally substituted C6-C12aryl groups and optionally substituted C1-C10alkyl groups. The alkyl groups may further be linear or branched, but are preferably not α-branched. The alkyl group may also comprise a cyclic system, provided it comprises at least 3 carbon atoms.

More in particular, the present invention relates to a copolymer according to Formula (II):

wherein:R1is selected from the group consisting of, optionally substituted, 2-pyridyl, 3-pyridiyl and 4-pyridyl groups, wherein R1is at position 2 or 3 of the phenol ring;R2is selected from the group consisting of, optionally substituted, 2-pyridyl, 3-pyridiyl, 4-pyridyl and phenyl groups, wherein R2is at position 5 or 6 of the phenol ring;the phenol ring bearing R1and R2is optionally substituted at one or two positions, independently selected from positions 2, 3, 5 and 6, with a halogen atom, with an optionally substituted C6-C12aryl group or a with an optionally substituted C1-C10alkyl group; andone or two substituents selected from the group consisting of R3, R4, R5and R6are an, optionally substituted phenyl group, whereas the other substituents selected from the group consisting of R3, R4, R5and R6are selected from the group of hydrogen, halogen and optionally substituted C1-C10alkyl groups.

According to the present invention, it is preferred that R2is selected from the group consisting of, optionally substituted, 2-pyridyl, 3-pyridiyl, 4-pyridyl groups.

It is furthermore preferred that R1and R2are an optionally substituted 2-pyridyl group.

It is also preferred according to the present invention that R1and R2are an optionally substituted 3-pyridyl group.

Additionally, in the copolymer according to Formula (II), R1is preferably at position 2 of the phenyl ring.

It is also preferred that R2is at position 6 of the phenyl ring.

Preferably, R3and R6are independently selected from the group of optionally substituted phenyl groups. Suitable substituents for the phenyl groups are fluorine and chlorine.

It is also preferred that in the copolymer according to Formula (II) that R4and R5are selected from the group of hydrogen, halogen, optionally substituted C6-C12aryl and optionally substituted C1-C10alkyl groups. As described above, the alkyl groups may be substituted with one or more halogen atoms, in particular halogen atoms selected from the group consisting of fluorine, chlorine and bromine atoms. The alkyl groups may further be linear or branched, but are preferably not α-branched. The alkyl group may also comprise a cyclic group, provided it comprises at least 3 carbon atoms.

The (co)polymers according to the present invention have generally a number average molecular weight Mnof about 7,000 to about 300,000 and a weight average molecular weight Mwof about 15,000 to about 1,000,000.

The present invention further relates to a process for polymerising a phenol compound according to Formula (I), wherein the phenol compound, optionally in the presence of a comonomer, is polymerised in the presence of a catalyst. According to the invention, it is preferred that the polymerisation is conducted in a solvent comprising a pyridine compound. More preferably, the solvent is a pyridine compound, in particular 3-chloropyridine.

According to the process of the present invention, it is preferred that the comonomer has the Formula (III):

wherein one or two substituents selected from the group consisting of R3, R4, R5and R6are an, optionally substituted phenyl group, whereas the other substituents selected from the group consisting of R3, R4, R5and R6are selected from the group of hydrogen, halogen, optionally substituted C6-C12aryl groups and optionally substituted C1-C10alkyl groups. As described above, the alkyl groups may be substituted with one or more halogen atoms, in particular halogen atoms selected from the group consisting of fluorine, chlorine and bromine atoms. The alkyl groups may further be linear or branched, but are preferably not α-branched. The alkyl group may also comprise a cyclic group, provided it comprises at least 3 carbon atoms.

The catalyst employed in the process according to the present invention preferably comprises a metal, preferably a metal from Group 6-12 of the Periodic Table of Elements (IUPAC version 22 June 2007 and Handbook of Chemistry & Physics 66thEd., 1985-1986; formerly Groups 6b-2b, cf. Handbook of Chemistry & Physics, 59th9 Ed., 1978-1979). Most preferably, the catalyst comprises copper, preferably having an oxidation state of at least 1+. Obviously, the catalyst may comprise copper species having different oxidation states.

The (co)polymer according to the present invention is preferably used for the manufacture of membranes, in particular membranes for fuel cells, and ion exchange resins.

EXAMPLES

Synthesis of 2,6-bis(3-pyridyl)phenol and its Polymerization

2,6-Bis(3-pyridyl)phenyl benzyl ether (16.70 g, 49.35 mmol) was dissolved in MeOH (200 mL). Argon was bubbled through this solution for 10 min to remove oxygen. Then Pd/C (500 mg 5 w %) was added, and the reaction mixture was put into the Parr-reactor and shaken for 16 hr under a hydrogen atmosphere at 80 psi. After the hydrogenation, the resulting precipitate was redissolved by heating to reflux. The hot mixture was filtered over diatomaceous earth, and the filter cake thoroughly washed with hot MeOH. Upon cooling to room temperature, the product crystallized as a white crystalline material (12.25 g, 99%). M.p.=211° C.1H-NMR (DMSO):δ=8.74 (d, 2H), 8.55 (dd, 2H), 7.95 (dt, 2H), 7.48 (m, 2H), 7.34 (d, 2H), 7.11 (t, 1H).

Polymerization of 2,6-bis(3-pyridyl)phenol

Cu(I)Cl (2.00 mg, 0.0202 mmol) and TMEDA (2.34 mg, 0.0202 mmol) were dissolved in 3-chloropyridine (2.5 mL). The mixture was heated to 85° C. and air was bubbled through for 10 min. Subsequently 2,6-bis(3-pyridyl)phenol (250 mg, 1.01 mmol) was added. The reaction mixture was heated for 16 hr at 85° C., while maintaining an air flow through the mixture. Then, it was cooled to room temperature and precipitated in diethyl ether (100 mL). The precipitate was washed thoroughly with diethyl ether, and dried in vacuo at 100° C. overnight. The polymer was obtained as a brown powder (220 mg, 88%). [η]=0.35 g/dl (0.1 w % in 95% H2SO4).

2-(3-pyridyl)phenyl benzyl ether (6.67 g, 25.52 mmol) was dissolved in MeOH (100 mL). Argon was bubbled through this solution for 10 min to remove oxygen. Then Pd/C (350 mg 5 w %) was added, and the reaction mixture was put into the Parr-reactor and shaken for 16 hr under a hydrogen atmosphere at 80 psi. After the hydrogenation, the mixture was filtered over diatomaceous earth, and the colourless solution was evaporated to dryness. The crude product was recrystallized from 2-propanol to yield a white crystalline material (3.54 g, 79%). M.p.=185° C.1H-NMR (CDCl3/MeOD):δ=8.76 (d, 1H), 8.43 (dd, 1H), 8.02 (dt, 1H), 7.39 (m, 1H), 7.21-7.29 (m, 2H), 6.95 (m, 2H).