WO2007114652A1

WO2007114652A1 - Novel benzimidazole monomers terminated with trifluorovinyloxy groups and polybenzimidazoles membrane prepared by using the same monomers

Info

Publication number: WO2007114652A1
Application number: PCT/KR2007/001650
Authority: WO
Inventors: Jeong-Hoon Kim; Soo Bok Lee; Bong-Jun Chang; In Jun Park; Dong-Kwon Kim; Jong-Wook Ha; Kwang-Won Lee; Kwang-Han Kim; Dong Jin Kim
Original assignee: Korea Research Institute of Chemical Technology KRICT
Current assignee: Korea Research Institute of Chemical Technology KRICT
Priority date: 2006-04-05
Filing date: 2007-04-04
Publication date: 2007-10-11
Anticipated expiration: 2008-10-05
Also published as: KR100744827B1

Abstract

The present invention relates to a fluorinated benzimidazole monomer comprising trifluorovinyloxy groups and a polymeric membrane prepared by using the fluorinated benzimidazole monomer, and particularly relates to a novel fluorinated benzimidazole monomer terminated with trifluorovinyloxy groups and a fluorinated benzimidazole polymer comprising a perfluorocyclobutane group. Due to a low surface energy of the perfluorocyclobutane group, this polymer shows improved processability, gas permeation, adhesiveness, low surface energy and low dielectric constant, while retaining superior thermal and chemical resistance, thus enabling the polymer membrane to be utilized as a material for fuel cell, gas permeation as an optical or electric or electronic material.

Description

NOVEL BENZIMIDAZOLE MONOMERS TERMINATED WITH

TRIFLUOROVINYLOXY GROUPS AND POLYBENZIMID AZOLES

MEMBRANE PREPARED BY USING THE SAME MONOMERS

TECHNICAL FIELD

The present invention relates to a fluorinated benzimidazole monomer

comprising trifluorovinyloxy groups and a polymeric membrane prepared by using

the fluorinated benzimidazole monomer. More particularly, the present invention

relates to a novel fluorinated benzimidazole monomer terminated with

trifluorovinyloxy groups and a fluorinated benzimidazole polymer comprising a

perfluorocyclobutane group. Due to a low surface energy of the

perfluorocyclobutane group, this polymer shows improved processability, gas

permeation, adhesiveness, low surface energy and low dielectric constant, while

retaining superior thermal and chemical resistance, thus enabling the polymer

membrane to be useful as a material for fuel cell, gas permeation as an optical or

electric or electronic material.

RELATED PRIOR ART

Polybenzimidazole has superior properties in various aspects such as

thermal stability, mechanical property and electrical insulating property, and has

been used as a material for intermediate level of insulation, high temperature gas separation, hemodialysis membrane, fuel cell membrane in the fields of aerospace

industry, electronic industry and a separation membrane

However, this polymer has poor solubility in common organic solvents, and

also has a problem of early thermal decomposition in fusion because of its high glass

transition temperature and fusion temperature.

Further, a gas separation membrane prepared by using polybenzimidazole is

low in permeability despite superior selectivity, which prevents polybenzimidazole

from being commercialized. As an electronic material, polybenzimidazole shows

high dielectric constant, which inhibits the micro-process thereof. Thus, there is

research in progress to introduce fluorine group in this polymer.

Despite outstandingly superior properties, the para-type polybenzimidazole,

commonly used for high temperature fuel cell membrane, has a problem that it is

not dissolved in an organic solvent, which prevents the mass production into a thin

film and delays its commercialization into a fuel cell membrane.

Therefore, there have been efforts made to introduce a fluorine group in the

polybenzimidazole to increase solubility in an organic solvent and gas permeability

with low dielectric constant while still maintaining its superior properties.

The present inventors have performed researches to develop

polybenzimidazole with improved solubility, gas permeability and low dielectric

constant, useful as a material for a fuel cell, gas separation or as an optical or electric

or electronic material. As a result, the inventors of the present invention found that a polymer

polymerized from a fluorinated benzimidazole monomer terminated with

trifluorovinyloxy groups shows improvements in properties such as staining

resistance, water resistance, oil resistance, processability and lower surface energy

and dielectric constant as compared with those of conventional polybenzimidazole.

Therefore, the preset invention aims to provide a fluorinated benzimidazole

monomer showing improvements in physical, electrical, optical and permeation

properties, and a polymer polymerized the aforementioned monomer.

The present invention also aims to provide a polymer membrane prepared

by using the fluorinated benzimidazole monomer.

DETAILED DESCRIPTION OF INVENTION

According to one aspect of the present invention, there is provided a fluorinated benzimidazole monomer terminated with trifluorovinyloxy groups formula (1):

wherein J ^Ai T is I l] or I Ij I Il , and X is a direct bond, -O-, -S-, -

CO-, -SO₂-, -SO- or -C(CF₃)Z-.

According to another aspect of the present invention, there is provided a method of preparing a fluorinated benzimidazole monomer terminated with trifluorovinyloxy groups of formula (1) as set forth in the Scheme 1. Scheme 1

(2) (4)

(6)

(1)

In the first step (i.e. step (a)), methyl(bromotetrafluoroethoxy)benzoate of

formula (4) is prepared by reacting hydroxybenzoate of formula (2) and

dibromotetrafluoroethanol of formula (3) in the presence of water or a polar aprotic

solvent, alkaline earth metal or a precursor compound thereof.

The water or aprotic polar solvent is used as a reaction solvent, and any

commonly-used aprotic polar solvent such as dimethylsulfoxide (DMSO), N-methyl-

2-pyrrolidone (NMP), dimethylformamide (DMF) and dimethylacetamide (DMAc)

may be used as the aprotic solvent.

This reaction solvent is preferably used in such an amount as to maintain the concentration of total monomers of formulas 2 and 3 within 1-40 wt%. If the

concentration is below 1 wt% the reaction rate becomes slowed down thus reducing

efficiency, while if the concentration exceeds 40% it increases viscosity when sodium

is substituted for the monomer of formula 2, thus inhibiting the reaction.

Further, the alkaline earth metal or the precursor compound thereof is used

to cause the dehydrogenation reaction, and may be selected among Na, NaH, NaOH

and KOH. Particularly, NaOH or KOH is preferred when water is used as the

reaction solvent. This alkaline earth metal or precursor compound thereof is

preferred to be in a molar ratio of 1-2 relative to the monomer of formula 2. The

molar ratio below 1 inhibits enough reaction, while economical efficiency or reaction

yield is low due to remaining the alkaline earth metal or precursor compound

thereof when the molar ratio is above 2.

The reaction is preferred to be performed at 0-50 ⁰C for 1-48 hours. The

solvent becomes solidified at a temperature below 0 ⁰C, thus inhibiting an efficient

reaction, while the temperature above 50 °C makes it difficult to control temperature

because of the exothermal nature of the reaction.

In the second step (i.e. step (b)), imidazole benzoate compounds of formula

(6) is prepared by dissolving and reacting the methyl(bromotetrafluoroethoxy)

benzoate of formula (4) and amine compounds of formula (5). The dissolution was

performed at a temperature where dissolution is possible, specifically at 150-250 ⁰C

by using poly(phophoric acid). In the third step (i.e. step (c)), fluorinated benzimidazole monomer of

formula (1) is prepared by oxidizing the imidazole benzoate compounds of formula

(6) in an organic solvent with high polarity.

Any organic solvent may be used only if the compound of formula 6 is

dissolved in the solvent, and specifically CHsCN, di-glycol methyl ether (diglyme),

tetrahydrofuran (THF), dioxane may be used as the organic solvent. This organic

solvent is preferred to be used in an amount of 5-40 wt% relative to the weight o f

total reactants. Reaction efficiency may be lowered when the amount is below 5

wt %, while the amount above 40 wt% causes viscosity inappropriate for reaction.

Further, imidazole benzoate compound of formula 6 is oxidized to introduce

a double bond according to the conventional oxidation method, for example by

using zinc powder as used herein.

Thus prepared fluorinated benzimidazole monomer is melted or dissolved in

a solvent with high boiling point, and heated up to 150-250 ⁰C, to provide a

fluorinated polymer of formula 7. In this reaction, almost all the monomer are used

to form the polymer as below substantially without any side reaction.

wherein I Ar I is I Ij or I IJ I Ij ; X is a direct bond, -O-, -S-, -CO-,

-SO₂-, -SO- or -C(CF₃)2-; and n is an integer of from 50 to 1,000.

This polymer is prepared by introducing perfluorocyclobutane group with superiority in chemical resistance and thermal stability into conventional

polybenzimidazole, thus resulting in superiority in staining resistance, water

resistance, oil resistance, processability and solubility as compared to those of

conventional polymers.

Meanwhile, the present invention also relates to a polymer membrane

prepared according to conventional methods by using the fluorinated polymer of

formula 7.

Hereunder is provided a detailed description of the method of preparing

membrane by using the fluorinated polymer formula 7.

First, the polymer of formula 7 is dissolved in an organic solvent to prepared

a polymer solution, and coated on the surface of support such as a porous polymer

or solid, followed by drying, thus forming a film. The coating may be performed

according to conventional methods such as bar coating, roll coating, flow coating,

deep coating, comma coating, blade coating, dye coating or spin coating method.

The organic solvent may be selected among those which are not involved in

chemical reaction, such as dimethylsulfoxide (DMSO), dimethylacetate (DMAc),

dimethylformamide (DMF) and N-methyl-2-pyrrolidone (NMP). Further, any

support commonly used as a membrane support may also be used in the present

invention (e.g. glass, metal, ceramic and polymer such as polysulfone or

poly ether amide).

The step of drying was performed at 50-200 ⁰C under normal pressure or vacuum for from 10 minutes to 24 hours, which is a common condition in a

conventional method.

This polymer membrane may be prepared into any form including a film, a

thin film, a flat sheet membrane, a hollow fiber membrane, a composite membrane

or a tubular membrane, and may be used in various technical fields, especially fuel

cell, gas separation, optical and electric or electronic material as a pervaporation

membrane, reverse osmosis membrane, gas separation membrane and fuel cell

membrane.

BRIEF DESCRIPTION OF DRAWINGS

Figure 1 is a hydrogen nuclear magnetic resonance (¹H NMR) spectrum of a

fluorinated polybenzimidazole comprising perfluorocyclobutane groups prepared in

Example 1.

Figure 2 is a fluorine nuclear magnetic resonance (¹⁹F NMR) spectrum of a

Example 1.

Figure 3 is a hydrogen nuclear magnetic resonance (¹H NMR) spectrum of a

Example 2. Figure 4 is a fluorine nuclear magnetic resonance (¹⁹F NMR) spectrum of a

Example 2.

EXAMPLES

The present invention is described more specifically by the following

Examples. Examples herein are meant only to illustrate the present invention, but

in no way to limit the claimed invention.

Example 1

Under nitrogen condition_/ 4.8 g (0.2 mol) of NaH was added in 400 mL of

dimethylsulf oxide (DMSO), and then 30.4 g (0.2 mol) of methyl 3-(hydroxy)benzoate

was slowly added, followed by stirring. After hydrogen gas was generated, 52 g

(0.2 mol) of dibromotetrafluoroethane was slowly added for reaction. While

performing a reaction, an ice-water bath was used to maintain reaction temperature

below 30 ⁰C. After 16 hours, products were placed in a separatory funnel and ethyl

acetate was added, followed by washing with water. Water was removed with MgSO₄ and solvent was dried under vacuum. The dried products were separated

and filtered through a column filled with silica gel by using ethyl acetate and hexane,

thereby producing 43 g (0.13 mol) of final products (yield 65%).

ⁱH-NMR (CDCI₃, δ in ppm): 3.95 (s, 3H, OCH₃), 7.42-8.01 (various m, 4H, CH

arom.), ¹⁹F-NMR (CDCl₃, δ in ppm): -86.52 (s, -CF₂CF₂Br), -68.64 (s, -CF₂CF₂Br).

(D Preparation of 5,5'-bibenzimidazole-2,2'-di(methyl 3-(2-

bromotetrafluoroethoxy) benzoate)

polypriosphαric acid

BrF₂CF^CO — f S € I I / f ^"%— OCFoCF₂Br

Under nitrogen condition, 33.1 g (0.1 mol) of methyl 3-(2-

bromotetrafluoroethoxy)benzoate and 9.6 g (45 mmol) of 3,3'-diaminobenzidine

were added in 300 g of poly(phosphoric acid), and reaction was performed by

stirring with a mechanical stirrer at 150 ⁰C for 16 hours. Products were dropped in

distilled water and stirred overnight. Thus obtained precipitates were filtered and

placed in 10 wt% Na₂CO₃ solution for a day. After performing filtration again, the

products were washed with distilled water several times and dried under vacuum.

The dried products were separated and filtered through a column filled with silica

gel by using ethyl acetate and hexane, thus producing 26.3 g (34 mmol) of final products (yield 75%).

Η-NMR (DMSO, δ in ppm): 7.48-8.28 (various m, 14H, CH arom.), 13.22 (s,

2H, NH), ¹^F-NMR (CDCl₃, δ in ppm): -84.89 (s, -CF₂CF₂Br), -69.76 (s, -CF₂CF₂Br).

(H) Preparation of 5,5'-bibenzimidazole-2_/2^l-di(methyl 3-

(trifluorovinyloxy)benzoate)

Under nitrogen condition, 7.76 g (10 mmol) of 5,5'-bibenzimidazole-2,2'-

di(methyl 3-(2-bromotetrafluoroethoxy)benzoate) and 1.44 g (22 mmol) of zinc

powder were added in 30 mL of anhydrous di-glycol methyl ether (diglyme) and

heated up to 100 ⁰C with stirring. After 16 hours, products were filtered with

filtering paper and dried under vacuum. The dried products were separated and

filtered through a column filled with silica gel by using ethyl acetate and hexane,

thereby producing 3.92 g (6.8 mmol) of final products (yield 68%).

Η-NMR (DMSO, δ in ppm): 7.53-8.46 (various m, 14H₇ CH arom.), 13.26 (s,

2H, NH), ¹⁹F-NMR (DMSO, δ in ppm): -118.3 (dd, cxs-CF=CF₂), -124.9 (dd, trans-

CF=CCF₂), -135.8 (dd, ds-CF=CCF₂).

Il © Preparation of polymer and film by using 5,5'-bibenzimidazole-2,2'-di(methyl

3-(trifluorovinyloxy)benzoate) as monomer

diphenyl ether

Under nitrogen condition, 3.0 g of 5,5'-bibenzimidazole-2,2'-di(methyl 3-

(trifluorovinyloxy)benzoate) was added in 10 mL of anhydrous diphenyl ether, and

heated at 220 ⁰C for 48 hours. Products were dropped in excess methanol and

stirred overnight. Thus obtained precipitates were filtered and washed with

methanol several times and dried under vacuum, to provide 2.5 g of final products

(yield 83%).

¹H-NMR (DMSO, δ in ppm): 7.35-8.23 (various m, CH arom.), ¹⁹F-NMR

(DMSO, δ in ppm): -127.1—133.2. Intrinsic viscosity (Cannon-Fenske viscometer)

1.1 (g/dl)-ⁱ.

5 wt % solution of the obtained polymer in dimethylacetate (DMAc) was cast

on glass and dried at 80 ⁰C for a day, and dried under vacuum at 120 ⁰C for 10 hours,

to provide a polymer film. Example 2

CD Preparation of methyl 4-(2-bromotetrafluoroethoxy)benzoate

The same process was performed as in Example 1, except by using methyl 4-

(hydroxy)benzoate instead of methyl 3-(hydroxy)benzoate (yield 73%).

¹H-NMR (CDCl₃, δ in ppm): 3.93 (s, 3H, OCH₃), 7.28-8.11 (various m, 4H, CH

arom.), 1⁹F-NMR (CDCl₃, δ in ppm): -86.48 (s, -CF₂CF₂Br), 68.62 (s, -CF₂CF₂Br).

Preparation of 5,5'~bibenzirnidazole-2,2'-di(methyl 4-(2-

bromotetrafluoroethoxy)benzoate)

polyphosphoric acid

The same process was performed as in Example 1, except by using methyl 4-

(2-bromotetrafluoroethoxy)benzoate instead of methyl 3-(2-

bromotetrafluoroethoxy)benzoate (yield 77%).

¹H-NMR (DMSO, δ in ppm): 7.55-8.36 (various m, 14H, CH arom.), 13.13 (s,

2H, NH), ¹⁹F-NMR (CDCl₃, δ in ppm): -84.79 (s, -CF₂ CF₂Br), -69.71 (s, -CF₂F₂Br). (B) Preparation of 5,5'-bibenzimidazole-2,2'-di(methyl

(trifluorovinyloxy)benzoate)

The same process was performed as in Example 1, except by using 5,5'-

bibenzimidazole~2,2'-di(methyl 4-(2-bromotetrafluoroethoxy)benzoate) instead of

5,5'-bibenzimidazole~2_/2^l-di(methyl 3-(2-bromotetrafluoroethoxy)benzoate) (yield

71%).

¹H-NMR (DMSO, δ in ppm): 7.58-8.41 (various m, 14H, CH arom.), 13.26 (s,

2H, NH), 19F-NMR (DMSO, δ in ppm): -118.1 (dd, CZs-CF=CF₂), -124.6 (dd, trans-

CF=CCF₂), -135.4 (dd, CtS-CCF=CCF₂) .

Preparation of polymer and film by using S_/S'-bibenzimidazole^^'-d^methyl

4-(trifluorovinyloxy)benzoate) as monomer

di

The same process was performed as in Example 1, except by using 5,5'-

bibenzimidazole-2,2'-di(methyl 4-(trifluorovinyloxy)benzoate) instead of 5,5'-

bibenzimidazole-2,2'-di(methyl 3-(trifluorovinyloxy)benzoate) (yield 85%). ⁱH-NMR (DMSO, δ in ppm): 7.32-8.26 (various m, CH arom.), W-NMR

(DMSO, δ in ppm): -127.2—130.4. Intrinsic viscosity(Cannon-Fenske viscometer) 1.4

(g/dl)-¹-

Comparative Example

ic acid

Under nitrogen condition, 5 g (0.0257 mol) of dimethyl isophthalate and

5.507 g (0.0257 mol) of 3,3'-diaminobenzidine was added in 100 g of poly(phosphoric

acid), and reaction was performed by stirring with a mechanical stirrer at 190 ⁰C for

-^⁰ 16 hours. Products were dropwisely added into distilled water and stirred for a

day. Thus obtained precipitates were filtered and placed in saturated NaHCO3

aqueous solution for a day. After filtration, the products were washed with

distilled water and methanol several times and dried under vacuum. The intrinsic

viscosity (Cannon-Fenske viscometer) was 1.3 (g/dl)-¹.

¹⁵ 5 wt % solution of the polymer was in dimethylacetate (DMAc) was cast on

glass and dried at 80 ⁰C overnight, and dried under vacuum at 120 ⁰C to provide

polymer film. Experimental Example 1

Solubility was measured as described below by using the polymer prepared

in Examples 1-2 and Comparative Example, and the results are provided in TABLE 1.

Each film was placed in four kinds of excess solutions of dimethylacetate

(DMAc), dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP) and sulfuric

acid (H2SO4), followed by stirring at room temperature for a day, and then their

respective solubility was measured.

TABLE 1

As shown in TABLE 1, the polymers prepared in Examples 1 and 2 showed

superior solubility in various solvent as compared to the polymer prepared in

Comparative Example. Experimental Example 2

Glass transition temperature was measured as described below by using the

polymer prepared in Examples 1-2 and Comparative Example, and the results are

provided in TABLE 2.

Glass transition temperature was measured with DSC by heating each film

under nitrogen condition at the rate of 10 °C/min up to 500 ⁰C.

TABLE 2

As shown in TABLE 2, the polymers prepared in Examples 1 and 2 were

lower in glass transition temperature, which results in improved fusibility and

processability as compared to the polymer prepared in Comparative Example.

Experimental Example 3

Tensile elongation at break was measured by using the polymer films

prepared in Examples 1-2 and Comparative Example, and the results are provided in

TABLE 3. TABLE 3

As shown in TABLE 3, the polymers prepared in Examples 1 and 2 showed

thinner membrane thickness and improved tensile elongation at break as compared

to the polymer prepared in Comparative Example.

As set forth above, the polymer membrane herein comprising fluorinated

benzimidazole monomer showed an improvement in processability and solubility in

various solutions due to the introduction of flexible trifluorovinyloxy groups at

chain ends, while retaining superior mechanical strength of the conventional

membrane, thus being applicable to various shapes of polymer membranes.

Claims

CLAIMSWhat is claimed is:

1. A fluorinated benzimidazole monomer terminated with trifluorovinyloxy groups at both ends as represented by the formula (1):

wherein I Ax I is and X is a

direct bond, -O-, -S-, -CO-, -SO₂-, -SO- or -C(CFs)₂-.

2. A method of preparing a fluorinated benzimidazole monomer of formula (1), comprising steps of:

(a) preparing methyl(biOmotetrafluoroethoxy)benzoate of formula (4) by reacting hydroxybenzoate of formula (2) and dibromotetrafluoroethanol of formula (3) in the presence of alkali earth metal or a precursor compound thereof;

(b) preparing imidazole benzoate compounds of formula (6) by reacting the methyl(bromotetrafluoroethoxy)benzoate of formula (4) and amine compounds of formula (5); and

(c) preparing fluorinated benzimidazole monomer of formula (1) by oxidizing the imidazole benzoate compounds of formula (6):

(2) (4)

(6)

(i)

3. The method of claim 2, wherein the step (a) is performed in a polar aprotic solvent selected from the group consisting of dimethylsulfoxide (DMSO), N- methyl-2-pyrrolidone (NMP), dimethylformamide (DMF) and dimethylacetamide (DMAc).

4. The method of claim 2, wherein the alkali earth metal or its precursor compound is selected from the group consisting of Na, NaH, NaOH and KOH.

5. The method of claim 2, wherein poly(phosρhoric acid) is used in performing the step (b).

6. The method of claim 2, wherein zinc is used in performing the step (c).

7. A fluorinated polymer of formula (7):

wherein X is a direct bond, -O-, -S-, -

CO-, -SO₂-, -SO- or -C(CF₃)₂-; and n is an integer of from 50 to 1,000.

8. A membrane comprising a fluorinated polymer of polymer (7):

wherein I Ar | is I I] or I I I Il ; X is a direct bond, -O-, -S-,

CO-, -SO₂-, -SO- or -C(CF₃)₂-; and n is an integer of from 50 to 1,000.

10

9. The method of claim 8, wherein the membrane has a shape selected from the group consisting of a film, a thin film, a flat sheet membrane, a hollow fiber membrane, a composite membrane and a tubular membrane.

^⁵ 10. The method of claim 8, wherein the membrane is used as a material for a fuel cell, gas separation or as an optical or electric or electronic material.