EP0915927A1

EP0915927A1 - Chiral nematic polycarbonates

Info

Publication number: EP0915927A1
Application number: EP97918961A
Authority: EP
Inventors: Peter Schuhmacher; Hans R. Kricheldorf; Shin-Jieh Sun
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 1996-08-05
Filing date: 1997-08-05
Publication date: 1999-05-19
Also published as: DE19631658A1; AU4298097A; WO1998005698A1; AU740373B2; US6156866A; JP2000515574A

Abstract

Liquid crystal chiral nematic polycarbonates are disclosed.

Description

Chiral ne atic polycarbonates

description

The invention relates to liquid-crystalline chiral nematic polycarbonates.

When heating anisotropic substances, liquid-crystalline phases, so-called mesophases, can occur. The individual phases differ in the spatial arrangement of the molecular centers on the one hand and in the molecular arrangement with respect to the longitudinal axes on the other (G. Gray, P A. Winsor, Liquid Crystals and Plastic Crystals, Ellis Horwood Limited, Chichester 1974). The nematic liquid-crystalline phase is characterized by the parallel orientation of the longitudinal axes of the molecules (one-dimensional order). Provided that the molecules that make up the nematic phase are chiral, a so-called chiral nematic (cholesteric) phase is created in which the longitudinal axes of the molecules form a helical superstructure that is perpendicular to it (H. Baessler, Solid State Problems XI, 1971). The chiral part of the molecule can either be present in the liquid-crystalline molecule itself or be added to the nematic phase as a dopant, the chiral nematic phase being induced. This phenomenon was first investigated on cholesterol derivatives (e.g. H. Baessler, M. M. Labes, J. Chem. Phys. 52, 631 (1970).

The chiral nematic phase has special optical properties: high optical rotation and a pronounced circular dichroism, which is created by selective reflection of circularly polarized light within the chiral nematic layer. The colors, which appear different depending on the viewing angle, depend on the pitch of the helical superstructure, which in turn depends on the twisting power of the chiral component. The pitch and thus the wavelength range of the selectively reflected light of a chiral nematic layer can be varied in particular by changing the concentration of a chiral dopant. Such chiral nematic systems offer interesting possibilities for practical use. Thus, by incorporating chiral parts of the molecule into esogenic acrylic acid esters and orientation in the chiral nematic phase, for example after photocrosslinking, a stable, colored network can be produced, the concentration of chiral component of which can then no longer be changed (G. Galli, M Laus, A. Angelon, Makromol. Chemistry 187, 2289 (1986)). By adding non-crosslinkable chiral compounds In nematic acrylic acid esters, a colored polymer can be produced by photocrosslinking, which still contains high proportions of soluble components (I. Heyndricks, DJ Broer, Λfol. Cryst. Liq. Cryst. 203, 113 (1991)). Furthermore, by statistical hydrosilylation of mixtures of cholesterol derivatives and acrylate-containing mesogens with defined cyclic siloxanes and subsequent photopolymerization, a chiral nematic network can be obtained in which the chiral component can have a share of up to 50% in the material used ; however, these polymers still contain significant amounts of soluble components (FH Kreuzer, R. Mauerer, Ch. Müller-Rees, J. Stohrer, Lecture No. 7, 22nd Working Conference on Liquid Crystals, Freiburg, 1993).

5 DE-A-35 35 547 describes a process in which a mixture of cholesterol-containing monoacrylates can be processed to chiral nematic layers via photo-crosslinking. However, the total proportion of the chiral component in the mixture is approximately 94%. As a pure side chain polymer, such a material is not mechanically very stable, but an increase in stability can be achieved by highly cross-linking diluents.

Numerous chiral nematic polyesters in which the mesogenic structures are built into the main chain are also generally known, e.g. from S. Vilasagar, A. Blumstein, Λfol. Cryst. Liq. Cryst. (1980), 56 (8), 263-9; A. Blumstein, S. Vilasagar, S. Ponratham, S. B. Clough, R.B. Blumstein, G. Maret, J. Polym. Be . , Polym. Phys. Ed. (1982), 20 (5), 877-92; E. Chiellini, G. Galli, 0 C. Malanga, N. Spassky, Polym. Bull (1983), 9 (6-7), 336-43); H. J. Park, J.I. Jin, R.W. Leng, Polymer (1985), 26 (9), 1301-6; J.I. Jin, E.J. Choi, K.Y. Lee, Polym. J. (1986), 18 (1), 99.101; J.I. Jin, S.C. Lee, S.D. Chi, J.H. Chang; Pollimo (1986), 10 (4), 382-8; J.I. Jin, E.J. Choi, B.W. Jo, Pollimo

1986, 35: 10 (6), 635-40; J.M.G. Cowie, H.H. Wu, ΛfaΛ: ro-nol. Chem. (1988), 189 (7), 1511-16; V. V. Zuev, I. G. Denisov, S. S. Skorokhodov, Vysokomol. Soedin. , Ser. A (1989, 31 (5), 1056-61; AS Angeloni, D. Caretti, C. Carlini, E. Chiellini, G. Galli, A. Altomare, R. Solaro, M. Laus, Liq. Cryst. (1986 ), 4 (5), 513-27;

40 K. Fujishiro, R. W. Lenz, Macromolecules (1992), 25 (1), 88-95; K. Fujishiro, R. W. Lenz, Macromolecules (1992), 25 (1), 81-7; V. V. Zuev, I. G. Denisov, S. S. Skorokhodov, Vysokomol. Soedin. , Ser. B (1992), 34 (3), 47-54); V. V. Zuev, I. G. Denisov, S. S. Skorokhodov Vysokomol. Soedin. , Ser. B (1989), 31 (2),

45 130-2. These polyesters generally show narrow areas of existence of the chiral nematic phase and contain predominantly open-chain chiral components which have a low twistability, so that relatively large proportions of these components are necessary in order to achieve a color impression. This limits the selection of the remaining polyester components, for example with regard to their mechanical properties.

DE-A-19504913.6 describes chiral nematic polyesters with chiral diol components with a strong twisting action, in particular dianhydro sugars, and broad liquid-crystalline phase ranges.

EP-A-682 092 describes paints based on chiral nematic polymers. Examples are only polyesters which have been prepared by polycondensation of dicarboxylic acids and diols. Polycarbonates are not mentioned.

Chiral nematic polycarbonates were previously unknown. Because of its nonlinear structure, the carbonate group is less suitable than the ester group for stabilizing a liquid-crystalline phase. Nevertheless, it has been possible to produce aromatic polycarbonates which contain para-linked diphenols, in particular 4, 4'-dihydroxybiphenyl (DHB) and can form a nematic phase over a wide temperature range (Kricheldorf, HR; Lübbers, D., Makromol. Rapid Communc. 1989, 10, 383; Kricheldorf, HR; Lübbers, D., Macromolecules 1990, 23, 2656; Sun, S.-J .; Chang, TzCh., J. Polym. Sei., Part A, Polym. Chem. 1993, 31, 2237). However, the use of chiral comonomers is problematic since they more destabilize the liquid-crystalline phase of polycarbonates than their non-chiral analogues.

The invention relates to chiral nematic polycarbonates with carbonate units which comprise a mesogenic group and carbonate units which comprise a chiral group and chiral nematic polycarbonates which additionally contain carbonate units with a photoreactive group and / or carbonate units with a further, non-chiral group, which is, in particular, a mesogenic and / or solubility-improving group. The units mentioned are groups which can be derived from diols by removing the two hydroxyl groups. They are therefore also referred to below as diol units.

Preferably corresponding to the chiral nematic polycarbonates of the formula I according to the invention ⁽ -0-A-OC) w \ (_ o-B-0-C)

XV OD — OC> Λ (-0-E-0-C) _,

wherein the molar ratio w / x / y / z is about 1 to 20 / about 1 to 5 / about 0 to 10 / about 0 to 10. A molar ratio w / x / y / z of approximately 1 to 5 / approximately 1 to 2 / approximately 0 to 5 / approximately 0 to 5 is particularly preferred.

Formula I says

A for a mesogenic group of the formula

B for a chiral group of the formula

id), (isoidide)

S— CH ₂ .- CH ₂

H H H

D for a photoreactive group of the formula

or

and

E for a further, non-chiral group of the formula

where L in the above formulas is alkyl, alkoxy, halogen, COOR, OCOR, CONHR or NHCOR, X is S, O, N, CH ₂ or a single bond, R is alkyl or hydrogen, A is a single bond, (CH ₂ ) _n , 0 (CH ₂ ) _n / S (Cu ₂ ) _n , NR (CH ₂ ) _n .

CH ₂ H \, CH ₂ CH ₂ H \, H \ X (T)

or means R ^{1 is} hydrogen, halogen, alkyl or phenyl and

n is an integer from 1 to 15.

When R ^{1 is} alkyl, halogen and A is a single bond or when R ^{1 is} H or alkyl and A is 0 {CH ₂ ) _{n (} S (CH ₂ ) _n or NR (CH ₂ ) _n

stands, they are solubility-improving groups. examples for this are

Isosorbide, isomannide and / or isoidide is the preferred chiral component.

Sugar derivatives based on dianhydrosorbide and the stereoisomers thereof are characterized by a very high twisting capacity. By a suitable choice of the ratio between the chiral diol and a non-chiral diol, preferably phenylhydroquinone, the liquid-crystalline phase ranges can be stabilized beyond 450 ° C.

The proportion of the chiral diol structural units is preferably in the range from 1 to 80 mol% of the total content of diol structural units, particularly preferably 2 to 20 mol%, depending on the desired interference color.

The following abbreviations apply in the context of the present application: 4, 4'-Dihydroxybiphenyl: DHB; Methylhydroquinone: MHQ; 4,4'-di-hydroxychalcon: DHC; Hydroquinone 4-hydroxybenzoate: HQHB; 2,5-bis (4'-hydroxybenzylidene) cyclopentanone: BHBC. Alkyl (also in alkoxy, etc.) is preferably Ci-C _ß alkyl, in particular Cι-C ₄ alkyl, such as methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, sec- Butyl, tert-butyl, n-pentyl and n-hexyl.

Shark stands for F, Cl, Br and I.

The polycarbonates according to the invention can be prepared by various types of polycondensation of diols with phosgene or diphosgene. Examples of diols which can be used are the terminally hydroxylated groups A, B, D and E of the formula I. They are in the molar ratio A / B / D / E * = 1 to 20/1 to 5/0 to 10/0 to 10, particularly preferably in the molar ratio A / B / D / EP = * 1 to 5/1 to 2/0 to 5/0 to 5. Densationsarten usual polycondensation, for example, interfacial polycondensation, _S chmelzpolykondensation and solution polycondensation.

In interfacial polycondensation, the diols forming the mesogenic group, the chiral group and, if appropriate, the photoreactive and the solubility-improving group, together with phosgene or preferably the much less dangerous diphosgene (CI-COCCI ₃ ) or triphosgene and a catalytic amount of an amine, for example triethylamine or a quaternary ammonium salt such as triethylbenzylammonium chloride in a suitable organic solvent, for example an ether such as tetrahydrofuran or dioxane, a chlorinated hydrocarbon such as dichloromethane or chlorobenzene. An aqueous base, for example sodium hydroxide solution, is added to this solution and the two phases are mixed with one another, for example by vigorous stirring. Cooling is preferably carried out while stirring. If the polymer is soluble in the solvent used, the organic phase is separated off and the polycarbonate is obtained therefrom in a customary manner, for example by taking up in methanol and filtering off. If, on the other hand, the polymer precipitates out of the solvent or if gel formation occurs, the reaction mixture is diluted if necessary, for example with methanol, and the polymer is filtered off. As an alternative to phosgene or diphosgene, the chlorinated carbonic acid diesters of the diols to be condensed can also be used.

In melt polycondensation, the dicarbonate of one of the diols forming the mesogenic group, the chiral group and optionally the solubility-improving or the photoreactive group is reacted with the diols forming the remaining groups. The reaction is carried out at a higher temperature, generally in the range from 120 ° C. to 300 ° C., the temperature in this range also being able to be increased in stages. The polymer obtained is dissolved or suspended in one of the suitable solvents mentioned above and optionally precipitated with methanol.

In solution polycondensation, the diols forming the mesogenic group, the chiral group and optionally the further non-chiral group and the photoreactive group are dissolved in an amine, preferably a tertiary or aromatic amine, for example pyridine. Diphosgene dissolved in one of the abovementioned suitable solvents is added to this solution. The reaction temperature is generally in the range from about 0 ° C to ambient temperature, but it can also be higher, in particular to complete the reaction. The mixture is then worked up in the usual way. As an alternative to the use of diphosgene, the chlorinated carbonic acid diesters of the diols to be polymerized can also be used in solution polycondensation. 5

Of the condensation methods mentioned, the interfacial polycondensation and the solution polycondensation are preferred, the latter particularly when more hydrophilic monomers, such as isosorbide, are used which interfere much more poorly with the interfacial polycondensation from the aqueous phase into the organic phase than the other monomers with them they are to be condensed.

If a low viscosity of the polycarbonate is desired, a chain terminator, e.g. Cinnamic acid chloride can be added.

The polycarbonates according to the invention have an inherent viscosity ηin _h of about 0.08 to 3 dl / g, in particular about 0.1 to 20 2 dl / g, measured at 20 ° C. with c = 2 g / 1 in dichloromethane / trifluoroacetic acid (Volume ratio 4/1).

The glass transition temperature (determined by means of DSC) of the polycarbonates according to the invention is generally in the range from about 50 to 25 300 ° C., in particular about 60 to 200 ° C. The melting temperature of the polymers according to the invention is generally in the range from approximately 75 to 450 ° C., in particular approximately 90 to 350 ° C.

The polycarbonates according to the invention contain statistically distributed units.

The polycarbonates according to the invention are capable of forming a so-called "grand jeans texture", which confirms the cholesteric effect of the chiral groups used.

35

The polymers according to the invention are particularly suitable as surface coating materials, as optical components and as chiral nematic colorants. They can be used as a coloring paint system for coating surfaces (e.g. as automotive paint

40 or effect films), or can also be used to produce pigment pigments. The color-giving structure of the polymer can be fixed by rapid cooling or photochemical crosslinking of the chiral nematic phase. The production of color pigments can e.g. by detaching the oriented polymer

45 films from the coated surface and grinding into platelet-shaped pigments. In contrast to the processes described in DE-A 42 40 743, this is crosslinking of the polymer is not absolutely necessary. The polymer can be used as a coating system as a powder coating, in the melt or in solution (for example in N-methylpyrrolidone or dimethylform amide). In the simplest case, the system is oriented by tempering the coated surface and can be improved if necessary by the action of mechanical, electrical or magnetic forces.

The following examples illustrate the invention without, however, restricting it:

The physical properties of the polymers described in the examples are given in Table 1.

example 1

Chiral nematic polycarbonate with (S) - (2-methylbutyl) thiohydroquinone as the chiral group-forming diol

DHB (15 mmol), MHQ (7.5 mmol), (S) - (2-methylbutyl) thiohydroquinone (7.5 mmol), diphosgene (16.5 mmol) and 1 drop of triethylamine were dissolved in 100 ml of dry cold dichloromethane . 80 ml of an IN sodium hydroxide solution were added to this solution and both phases were stirred for 10 minutes with an "Ultra Turrax" high-speed stirrer and then for 20 minutes with a normal mechanical stirrer while cooling with ice. The organic phase was then separated off in a separating funnel, placed in 800 ml of methanol and filtered. The isolated polymer was dissolved in dichloromethane and reprecipitated in methanol. Finally, the polycarbonate was dried at 80 ° C in a vacuum. The yield of this interfacial polycondensation was 88%. The resulting polymer 1 is described by the following formula:

with the molar ratio x / y / z = 5/1/4.

Example 2

Chiral nematic polycarbonates with isosorbide as the chiral group-forming diol A solution of diphosgene (16.5 mmol) in 20 ml dichloromethane was added dropwise into a solution of DHB (15 mmol), MHQ (7.5 mmol) and isosorbide (7.5 mmol) in 30 ml pyridine. The mixture was allowed to react at about 5 to 10 ° C for 30 minutes and then at room temperature for about an hour. The mixture was then poured into methanol and filtered. The isolated polymer was dissolved in dichloromethane and reprecipitated in methanol. The resulting polycarbonate of formula 2 with the molar ratio x / y / z = 2/1/1 (2a) was dried at 80 ° C in a vacuum. In the same way, however, with 3.75 mmol MHQ and 11.25 mmol isosorbide, a second polycarbonate of the formula 2 with the molar ratio x / y / z = 4/1/3 (2b) was produced.

In both cases the yield was 98%

Example 3

Chiral nematic polycarbonates with DHC as a photoreactive group

A solution of diphosgene (16.5 mmol) in dichloromethane (20 ml) was added dropwise to a solution of DHB (15 mmol), DHC (7.5 mmol) and isosorbide (7.5 mmol) in pyridine (30 ml) . The reaction mixture was stirred at about 5 to 10 ° C. with ice cooling for 30 minutes and subsequently at about 20 to 25 ° C. for about 1 hour. The reaction mixture was then poured into cold methanol and the precipitated polycarbonate of formula 3

filtered with the molar ratio x / y / z = 2/1/1 (3a), washed with methanol and dried at about 80 ° C in a vacuum. Analogously, three further polycarbonates with the molar ratios x / y / z = 3/2/1 (3b), x / y / z = 4/3/1 (3c) and x / y / z = 5/4 / 1 (3d). The amounts of DHC or isosorbide used for 3b and 5 mmol 10 mmol, mmol mmol and 3d 12 and 3 mmol of 3c 11.25 mmol or ^". 3.75. The yield was for 3a-c respectively 98%, for 3d 97%. A 5- Minutes of UV radiation of thin films of polycarbonates 3a to 3d with a mercury vapor lamp caused the polymers to become insoluble in dichloromethane, making DHC also suitable as a crosslinker in chiral nematic polycarbonates.

Example 4

Chiral nematic polycarbonates with HQHB as the mesogenic group-forming diol

A solution of diphosgene (16.5 mmol) in 20 ml dichloromethane was added dropwise to a solution of HQHB (15 mmol), DHC (7.5 mmol) and isosorbide (7.5 mmol) in 30 ml pyridine. The mixture was allowed to react at about 5 to 10 ° C for about 30 minutes and then at room temperature for about an hour. The mixture was then taken up in methanol and the precipitated polycarbonate of the formula 4

filtered with the molar ratio x / y / z = 2/1/1 (4a) and dried at about 80 ° C in a vacuum. Three other polycarbonates with the molar ratios x / y / z = 3/2/1 (4b), x / y / z = 4/3/1 (4c) and x / y / z = 5/4/1 (4d) were prepared in an analogous manner. The amounts of DHC or isosorbide used were 10 mmol or 5 mmol for 4b, 11.25 mmol or 3.75 mmol for 4c and 12 mmol or 3 mmol for 4d. The yields were 94% for the polycarbonate 4a, 93% for 4b and 96% for 4c and 4d, respectively.

Example 5

Chiral nematic polycarbonates with BHBC as a crosslinker

A solution of diphosgene (16.5 mmol) in 20 ml dichloromethane was added dropwise to a solution of HQHB (10 mmol), BHBC

(10 mmol) and isosorbide (10 mmol) in 30 ml of pyridine. The mixture was left at about 5 to 10 ° C for about 30 minutes and then about react for one hour at room temperature. Then the mixture was poured into methanol and filtered. The polymer of formula 5 obtained

with the molar ratios x / y / z = 1/1/1 (5a) was dissolved in dichloromethane and precipitated again in methanol. Finally, the polycarbonate was dried in vacuo at about 80 ° C. Three further polycarbonates of the formula 5 were produced in the same way. The molar ratios x / y / z were 2/1/1 for 5b, 3/2/1 for 5c and 4/3/1 for 5d. The amounts of HQHB, BHBC and isosorbide used were 15 mmol, 7.5 mmol and 7.5 mmol for 5b, 15 mmol, 10 mmol and 5 mmol for 5c and 15 mmol, 11.25 mmol and 3.75 mmol for 5d . The yield was 84% for 5a, 91% for 5b, 79% for 5c and 90% for 5d.

Table 1 shows the physical properties (inherent viscosity (ηi _nh ), rotation value ([α] _D ), glass level (T _g ) and clearing point (Ti)), the observed textures of the liquid-crystalline phases and the interference colors of polymers 1 to 5 .

Table 1

Poly ηinh ¹⁾ d [D] 2 ⁾ Tg ³ > Ti ⁴ > texture color or (dl / g) [degree] <° C) (° C) image oligomer

1 1.48 -1.2 115> 300 grand blue jean

2a 0.68 +43 121> 340> Grand bluish jeans

2b 0.86 +28 - (?)> 360 ^z 'Grand bluish jeans

3a 0.50 +41.6 116> 340 ^z »Grand bluish jeans

3b 0.38 +33.0 118> 340 ^z > Grand bluish jeans

3c 0.40 +21.1 116> 350 ^z > grand blue jean ₃ d 0.33 +19.6 111> 350 ^z) grand blue jean

4a 0.27 + 38.7 * 104 290-325 Grand blue in reflective jeans light, yellowish-orange in transparent light

4b 0.50 + 30.3 * 102 280-300 grand blue jean

4c 0.62 + 23.5 * 101 310-330 grand blue .jean 4d 0.66 + 17.1 * 101 325-> 350 grand blue jean

5a 0.58 146> 310 ^{z) v)} Grand Bluish Jean 5b 0.47 126> 315z) v) Grand Bluish Jean

5c 0.45 146> 330z) v) Grand bluish jeans

5d 0.88 135> 320 ^z ' ^v > Grand bluish jeans

¹ 'measured at 20 ° C, c = 2 g / 1 in dichloromethane / trifluoroacetic acid (4/1)

²⁾ measured at 25 ° C, c = 5 g / 1 or * 2 g / 1 in dichloromethane / trifluoroacetic acid (4/1)

3 ⁾ DSC measurement, heating rate 20 ° C / min ⁴ 'polarizing microscope, heating rate 10 ° C / min or * optical microscope, heating rate 20 ° C / min ^z ' thermal decay ^v 'thermal crosslinking

411 / hz

Claims

claims

1. Chiral nematic polycarbonates with carbonate units which comprise a mesogenic group and carbonate units which comprise a chiral group.

Chiral nematic polycarbonates according to claim 1, which additionally comprise carbonate units with a photoreactive group and / or carbonate units with a further, non-chiral group.

3. Chiral nematic polycarbonates according to claim 1 or 2 of formula I.

wherein the molar ratio w / x / y / z is about 1 to 20 / about 1 to 5 / about 0 to 10 / about 0 to 10,

for a mesogenic group of the formula

or stands

B for a chiral group of the formula

stands,

for a photoreactive group of the formula

or

stands, and

for another, non-chiral group of the formula

is in the formulas above L represents alkyl, alkoxy, halogen, COOR, OCOR, CONHR or NHCOR, X represents S, 0, N, CH or a single bond, R represents alkyl or hydrogen, A represents a single bond, (CH ₂ ) _n / 0 ⁽ CH ₂ ) _n , S (Cu ₂ ) _n - NR (CH ₂ ) _n ι ^, CH ₂ CH ₂ - ( ^H V- '' - ^χ - (θ) -

or means

R ^{1 is} hydrogen, halogen, alkyl or phenyl and

n is an integer from 1 to 15.

4. Chiral nematic polycarbonates according to one of the preceding

Claims, characterized in that their inherent viscosity is approximately 0.08 to 3 dl / g, in particular approximately 0.1 to 2 dl / g, measured at 20 ° C.

5. Chiral nematic polycarbonates according to one of the preceding

Claims, characterized in that their glass transition temperature is in the range of approximately 50 to 300 ° C, in particular approximately 60 to 200 ° C.

6. Use of the chiral nematic polycarbonates according to one of the preceding claims as an optical component or as a surface coating material.

7. Use of the chiral nematic polycarbonates according to one of claims 1 to 5 as a colorant, in particular as a coloring component of coating systems for coating surfaces or as a component of printing inks.

8. Use of the chiral nematic polycarbonates according to one of claims 1 to 5 in cosmetic products, in particular nail polishes and lipsticks.

9. Pigments containing chiral nematic polycarbonates according to one of claims 1 to 5.

10. coating compositions containing at least one chiral nematic polycarbonate according to one of claims 1 to 5 or at least one pigment according to claim 9.

11. A process for the preparation of chiral nematic polycarbonates according to any one of claims 1 to 5, characterized in that mesogenic groups and chiral groups and optionally photoreactive groups and / or solubility-improving groups and / or thermally crosslinking groups in each case in the form of the corresponding diol compounds Phosgene or diphosgene condensed.

12. The method according to claim 11, characterized in that cinnamoyl chloride is added as a chain terminator.

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