GB2298202A - Chiral polymerizable binaphthol derivatives - Google Patents

Abstract

Chiral polymerizable binaphthol derivatives have one or two side chains that contain functional groups at the end thereof, wherein the binapthol group and said functional groups are separated by at least one mesogen ring group and optionally a spacer group. Liquid crystalline materials in the form of a cholesteric polymer network are obtained by copolymerizing an achiral compound having one or two polymerizable functional groups and the binaphthol derivative.

Description

Chiral polymerizable binaphthol derivatives The invention relates to chiral polymerizable binaphthol derivatives of formula I

in which A is R-(+)- or S-(-)-1,1'-binaphthyl-2,2' -diyl X1 and X2 each independently denote -CO-, -CH2-, or a single bond MG1 and MG2 each independently denote a mesogenic group comprising 1 to 4 ring systems and optionally up to 3 bridging groups y1 and y2 are each independently -O-, -CO-O-, -O-CO- or a single bond Spi and Sp2 are each independently spacer groups with up to 20 C, O, and N atoms R1 is a polymerizabie group selected from the formulae CHZ =cw-co-o-,

H!A7N-, CH2=CH-, CH2=CH-O- or HS-(CH2)m-COO- with W being H, Cl or alkyl with 1-5 C atoms and m being 1-7, R2 is an optionally halogenated alkyl radical with up to 15 C atoms, it being possible for one or more CH2 groups to be replaced by -O-, -S-, -CO-, -CO-O-, -O-CO- or -O-CO-O in such a manner that oxygen atoms are not linked to one another, or R2 has the meaning given for R1, and m is 1, and n isOor1.

The invention further relates to a liquid crystalline material in the form of an anisotropic gel consisting of a polymerized monotropic or enantiotropic liquid crystalline material and a low-molecular weight liquid crystalline material, wherein the polymerized material a) forms a permanently oriented network in the low-molecular weight liquid crystalline material b), characterized in that the polymerized material a) is obtainable by (co)polymerization of a chiral polymerizable binapthol derivative.

In European Patent Application EP 451 905 a liquid crystalline material in the form of an anisotropic gel comprising a polymerized liquid crystalline material and a low-molecular nematic liquid crystalline material.

The European Patent Application EP 0 415 120 describes low-molecular weight binapthol derivatives.

There is not motivation to modify these compound to achieve polymerizable derivatives.

The European Patent Application EP 606 940 discloses a cholesteric polarizer based on chiral mesogenic diacrylates. Since those compounds exhibit long pitch lengths of the helical pitch comparable high amounts are necessary to achieve selective reflection in the visible region of the spectrum. There is a great demand for compounds with short pitch lengths which can be used as dopants to induce selective reflection in the visible region.

In accordance with the invention, chiral polymerizable binaphthol derivatives as described in the opening paragraph are obtained, which have very short pitch lengths.

Preferred embodiments of the invention are: a) Binaphthol derivatives according to Claim 1, in which MG1 and MG2 are independently

with L being CH3, -COCH3, -CN, F or Cl and r being 0, 1 or 2.

b) Binaphthol derivatives wherein the groups X1-MG1-Y1-Sp1-R1 and X2 MG2-Y2-Sp2-R2 are identical.

c) Binaphthol derivatives wherein X1 is CO, Y1 is-O-, Spr is -(CH2)k- with k being an integer between 2 and 12, and R1 is CH2=CW-COOd) A liquid crystalline material in the form of cholesteric polymer network, wherein the polymerized material is obtainable by copolymerization of a achiral compound (a) having one or two polymerizable functional groups and a chiral polymerizable compound (b), characterized in that (b) is a binaphthol derivative of formula 1.

e) A liquid crystalline material wherein the compound (a) is a bisacrylate of formula Il R3[(CH2)p-A]q-MG3[A-(CH2)p]q-R3 II wherein A is -O-, 0-0-, -0-CO- or a single bond1 has the meaning given for RI1 p and q are integers between 0 and 20, and MG3 has the meaning given for MG1 Another aspect of the present invention is a copolymerizable precursor material comprising at least one bifunctional reactive achiral compound of formula II and at least one mono or diseactive chiral compound of formula preferably a material comprising at least one bifunctional reactive achiral compound of formula II and at least one reactive chiral compound of formula I in which R1 is an acrylate radical of formula

wherein W has the meaning given or a material comprising at least one compound of formula II and at least one compound of formula I in which is a vinylether radical of formula CH2=CH-O-.Preferred embodiments are: Another aspect of the present invention is a cholesteric film obtainable by the steps comprising a) ordering the copolymerizable precursor material comprising a bifunctional reactive chiral compound of formula I and a bifunctional compound of formula II in the monomeric state in the presence of an UV initiator and optionally an additive, and b) in situ UV polymerization of the resulting ordered precursor material. Preferred compounds of formula I are those of formulae lal to ld6:

in which W has the meaning given, k is an integer between 2 and 10, and the phenylene rings are optionally substituted by fluorine.

Formula I covers chiral reactive liquid crystalline compounds with 2 rings of formulae la-lc: R1-Spl-Y1 -Phe'-COO-A-OCO-Phe'-Rz la R1-Sp1-Y1-Phe'-COO-A-OCO-Pyd-R2 Ib R1-Sp1-Y1-Phe'-COO-A-OCO-Pyr-R2 Ic and compounds with 3 rings of formulae Id to II: R1-Sp1-Y1-Phe'-COO-A-OCO-Phe"-Phe"-R2 Id R1-Sp1-Y1-Phe'-COO-A-OCO-Phe"-Pyr-R2 Ie R1-Spl -Y1-Phe'-COO-A-OCO-Phe"-Pyd-R2 If R1-Sp1-Y1-Nap-COO-A-OCO-Phe"-Phe"-R2 Ig R1-Sp1-Y1-Phe'-COO-A-OCO-Pyd-Phe"-R2 Ih R1-Spl-YI -Phe'-COO-A-OCO-Pyr-Phe"-R2 li R1-Sp1-Y1-Phe'-COO-A-OCO-Phe"-Z-Phe"-R2 Ij R1-Sp1-Phe'-Phe"-COO-A-OCO-Phe"-R2 Ik R1-Spr-Phe'-Z-Phe-COO-A-OCO-Phe"-R2 II Wherein R1, R2, Spr, Y1 and A have the meaning given, Pyd denotes pyrimidine-2,5-diyl and Pyr denotes pyridine-2,5-diyl.

Z denotes -CO4-, -O-CO-, -CH20-, -OCH2-, -CH2CHr, -C=-C- or a single bond.

In the compounds of formulae la-Il, Phe' denotes a 1,4-phenylene group

wherein X3-X6 denote independently from each other H or halogen or methyl.

In the compounds of formulae la-li, Phe" is a 1 ,4-phenylene group, which is unsubstituted or mono- or polysubstituted by CN or halogen, and Nap is a naphthaline-2,6-diyl group

which is unsubstituted or wherein up to 4 of X7-X12 are independently from each other halogen while the other denote H.

The compounds of formulae la-ll are preferred. Especially preferred are the compounds of formulae la, Id, Ij, Ik and 11.

In the compounds of formulae la-ll R1 is CH2 = CW-COO-,, CH2 = CH-O-, HW

,HWN-, HS-CH2-(CH2)m-COO- with W being H, CI or alkyl with 1-5 C atoms and m being 1-7.

Preferably, RI is a vinyl ether group, an acrylate group, an amino group or a mercapto group, and especially preferred are the following meanings of R1: CH2=CH-COO- R1-1

CH2=CH-O- R1-4 H2N- R1-5 H(alkyl)N- RI-6 HS-CH2-(CH2)m-COO- R1-7

with alkyl denoting C1-C3-alkyl and m being 1-5.

In the compounds of formulae la-il, the spacer-type group Spr is alkylene with up to 20 C atoms1 it is also being possible for one or more non adjacent CH2 groups to be replaced by O, S or NH.

In case Spi and/or Sp2 is alkyiene, Spi andlor Sp2 may be straight-chain or branched. Sp1 especially preferred is ethylene, propylene, butylene, 1 methyl-propylene, 2-methyl-propylene, pentylene, 1-methyl-butylene, 2 methyl-butylene, hexylene, 2-ethyl-butylene, 1,3-dimethyl-butylene, hephylene, 1-methylhexylene, 2-methylhexyiene, 3-methylhexylene, 4.

methylhexylene, 5-methylhexylene, 6-methylhexylene, octylene, 3-ethylheptylene, nonylene, 1-methyl-octylene, 2-methyloctylene, 7 rnethyloctylene, decylene, undecylene, dodecylene, 2 rnethylundecylene, 2,7,5-trimethyl-nonylene or 3-propyl-nonylene.

In case Sp1 andlor Sp2 is mono- or polyoxaalkylene, Spi and/or Sp2 may be straight-chain or branched. In particular, Sp1 is 1--oxa-ethylene, 1 -oxa propylene, 2-oxa-propylene, 1-oxa-butylene, 2-oxa-butylene,1,3 dioxa-butylene, 1-oxa-pentylene, 2-oxa-pentylene, 3-o-pentylene, 2-oxa 3-methyl-butylene, 1-oxa-hexylene, 2-oxa-hexylene, 3-oxa-hexylene, 1,3 dioxa-hexylene, 1,4-dioxa-hexylene, 1,5-dioxa-hexylene, 1-oxa-heptylene, 2-oxa-heptylene, 1,3-dioxa-heptylene, 1,4-dioxa-heptylene, 1,5-dioxa heptylene, 1 16-dioxa-heptylene, 1,3,5-trioxa-heptylene, 1exa-octylene, 2 oxa-octylene, 3-oxa-octylene, 4-oxa-octylene, 1,3-dioxa-octylene, 1,4 dioxa-nonylene, 1 14-dioxadecylene, 1,4-dioxa-undecylene and 1,3,5 trioxa-dodecylene.

yi and/or Y2 are -0-, -S-, -COO-, -OCO- or a single bond and in particular -O-, -COO-, -OCO- or a single bond. In case Y1 is -0-, -S- or -OCO-1 the adjacent CH2 < roup of Sp is not replaced by -O-.

Z is preferably -COO-, -OCO-, -CH2CHr or a single bond, in particular -CO-O- or a single bond.

R2 can be an alkyl radical with up to 15 C atoms which is unsubstituted, mono or polysubstituted by halogen, it also being possible for one or more CH2 groups in these radicals to be replaced, in each case independently from one another, by -O-, -S-, -CO-, -OCO-, -COO- or -O-COO- in such a manner that oxygen atoms are not linked directly to one another.

If R2 is each independently an alkyl radical or alkoxy radical, it may be straightchain or branched. Preferably, it is straightchain, has 2, 3, 4, 5, 6, 7 or 8 carbon atoms and accordingly is preferably ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, ethoxy, propoxy, butoxy, pentoxy, hexoxy, heptoxy or octoxy, and furthermore methyl, nonyl, decyl, undecyl, tridecyl, tetradecyl, pentadecyl, methoxy, nonoxy, decoxy, undecoxy, dodecoxy, tridecoxy or tetradecoxy. ~.

R2 is each independently oxaalkyl, it is preferably straight-chain 2 oxapropyi (= methoxymethyl), 2-oxabutyl (= ethoxymethyl) or 3-oxabutyl (= 2-methoxyethyl), 2-, 3- or 46xapentyl, 2-, 3-, 4- or 5-oxahexyl, 2-, 3-, 4-, 5- or 6-oxaheptyl, 2-, 3-, 4-, 5-, 6- or 7-oxaoctyl, 2-, 3-, 4-, 5-, 6-, 7-or 8oxanonyl, 2-, 3-, 4-, 5-, 6-, 7-, 8-, or 9-oxadecyl.

Preferred chiral radicals R2 are each independently, 2-butyl (= 1-methylpropyi), 2-methylbutyl, 2-methylpentyl, 3-methylpentyl, 2-ethylhexyl, 2-propylpentyl, 2octyl, in particular 2-methylbutyl, 2-methylbutoxy, 2-methylpentoxy, 3-methylpentoxy, 2-ethylhexoxy, 1-methylhexoxy, 2-octyloxy, 2-oxa-3-methylbutyl, 3-oxa4-methylpentyl, 4-methylhexyl, 2-nonyl, 2-decyl, 2-dodecyl, 6-methyloctoxy, 6-methyloctanyloxy, 5-methyl heptyloxycarbonyl, 2-methylbutyryl oxy, 3-methylvaleryloxy, 4-methylhexanoyloxy, 2-chloropropionyloxy, 2-chl oro-3-methyibutyryloxy, 2-chloro4-methylvaleryloxy, 2 chloro-3methylvaleryloxy, 2-methyl-3 oxapentyl, 2-methyl-3-oxahexyl, 1-meth oxypropyl-2-oxy, 1-ethoxypropyl2-oxy, 1-propoxypropyl-2-oxy, 1-butoxypropyl-2-oxy, 2-fluoro octyloxy, 2fluorodecyloxy.

R2 can also have one of the meanings given for R1 above. In case R2 is an - optionally substituted - alkyl radical, R1 preferably is a vinyl or acrylate group while in case R2 is RI, all meanings given above for R4 are preferred.

The compounds of formula I are obtained according to the following scheme.

Scheme

OH OH V CH2=CW-COO-Sp'-Y'-MG'-COCI DCMTTEA < CW=CH2 I OCO-MGI-Y'-Sp'-O I OCO-MG -Y -Sp1-OCO OCO-MG1-Y1-Sp1-OCO CW=CH2 The inventive display exhibits two opposite plates which are transparent to light and which will hereinafter be termed substrates and which comprise electrodes on the opposing sides, said electrodes being manufactured from, for example, In203 SnO2. On the electrode there is provided an orientation layer of, for example, robbed polyimide or polyamide by means of which the liquid crystalline material according to the invention can be homogeneously aligned between the electrodes.The cell is manufactured by arranging the substrates thus formed and provided with electrodes closing the apertures by, for example, a ringshaped member and filling the space between the substrates and the ring with the liquid crystalline material according to the invention.

The liquid crystalline material can be capillary filled between two substrates which are provided with electrode layers, and is then subsequently cured, for example, by irradiation with UV light, preferably in the presence of a photoinitiator, for example, a.n Irgacure. Another possible but less attractive technique comprises coating of the LC material on a substrate with subsequent curing. The film may be peeled off and arranged between 2 substrates provided with electrode layers. It is also possible that the substrate onto which the LC material is applied exhibits an electrode layer so that the electrooptical system can be obtained by applying a second electrode layer and, optionally, a second substrate onto the coated and cured film.

The electrooptical system according to the4nvention can be operated reflectively or transmissively so that at least one electrode and, if present, the associated substrate are transparent. Both systems customarily contain no polarizers, as a result of which a distinctty higher light transmission results and is a considerable technological simplification in the production of these systems compared with conventional liquid crystal systems such as, for example, TN or STN cells.

In general a nematic liquid crystal of positive dielectric anisotropy is desirable because these mixtures would be used in devices in which it is essential to electrically switch a thin film of such a mixture into a homeotropic alignment (field on state) and therefore appear clear to transparent, while the off state would usually be determined by the alignment within the cell, which is usually homogenous and this would give either focal conic (slightly scattering) or grandjean (coloured). It is possible that depending on how the voltage is applied or removed one can flip into either the coloured grand,ean or the slightly scattering focal conic state in the field off state.Moreover by adding a small amount of a liquid crystal each state can be stabilised to give a bistable device with one stage being colored (grandjean texture) or essentially clear or slightly light scattering (focal conic). When placed against a black background a contrast between colored and black is clearly seen. The color being dependent on the pitch length of the cholesteric helix according to the equation 1, = n P sin 0 = mean refractive index of the LC, P = pitch length 0 = viewing angle.

The pitch length obtained when adding a chiral dopant to a nematic host depends on the polarising ability 6f the LC molecules - the more polarisable they are the tighter the pitch length obtained (higher twisting power), so using a non-polar host may significantly alter how much chiral dopant would be needed to produce a given colour.

Another application for chiral binaphthol derivatives is to mix them with reactive liquid crystals (for example of formula II) and produce a chiral coloured reactive LC mixture which can be coated into a thin film and polymerised by UV light to give a thin polymer film which is coloured. It would contain 20-30 % non-reactive chiral LC as above therefore the polymer content is 70-80 %.

The rise time increases according as the cell thickness increases, but the decay time remains constant. The decay time decreases rapidly according as the content of network molecules increases. Consequently, it is not the thickness of the cell that counts but the average distance between the network molecules. This explains the short decay times in comparison with the decay times (a few hundred milliseconds) in normal nematic cells.

More particularly, decay times of a few milliseconds can be obtained.

The novel chiral reactive liquid crystalline compounds and compositions are highly suitable to produce cholesteric films which can be used in different optical and electrooptical applications.

Furthermore, they are useful as colored films for decorative appiications.

Since some of them show thermochromism, they can be used as temperature indicators, in particular as reversible or irreversible temperature indicators depending on their grade of polymerizations.

The invention will be explained in more detail by means of the following examples of the preparation of a liquid crystalline material according to the invention.

The mesogenic phases are abbreviated as following: K crystalline N nematic S smectic BP blue phase N chiral nematic (cholesteric) -- HTP helical twisting power P pitch length Examole 1 The chiral reactive mesogenic compound (1)

is prepared via the sequence of reaction steps shown in the above scheme.

1 mol of the R-(+)-1,1-binaphthol and 1.1 mol of benzoyl chloride are dissolved in 11 of dichlormethane. 1.1 mol of triethylamine are added, and the mixture is stirred for 3 hours at room temperature, the resulting liquid compound shows a very short pitch length P = 0.029 um and high HTP of 34.5. ~. f Example 2 A composition consisting of 5 % of the binaphthol derivative of example 1 and 5 % of a nematic liquid crystalline composition coded E63 (commercially obtainable from Merck Ltd., Poole, UK) shows a broad absorption band in the visible region between # = 800 and 1000 nm.

Examole 3 A mixture is formulated consisting of 10 % of the binaphthol of example 1, and

reflects selectively with a wavelength of maxlmumereflection of 650nm.

0.467 % by weight of a photoinitiator (coded KB 1) are added and the resulting mixture is aligned on rubbed PVA unidirectionally with 0.5% by weight of 16 urn spacers and is photopolymerized to achieve full polymerization and to give a chiral polymeric network with a selective reflection maximum of 650 nm.

Claims (7)

Claims

1. Chiral polymerizable binaphthol derivatives of formula I

in which A is R-(+)- or S-(-)-1 ,1'-binaphthyl-2,2'diyl X1 and X2 each independently denote -CO-, -CH-, or a single bond MG1 and MG2 each independently denote a mesogenic group comprising 1 to 4 ring systems and optionally up to 3 bridging groups y1 and Y2 are each independently -0-, -CO-O-, -O-CO- or a single bond Sp1 and Sp2 are each independently spacer groups with up to 20 C, O, and N atoms R1 is a polymerizable group selected from the formulae CH2=CW-CO-O,

HWN, CH2=CH-, CH2=CH-O- or HS-(CH2)m-COO- with W being H, CI or alkyl with 1-5 C atoms and m being 1-7, R2 is an optionally halogenated alkyl radical with up to 15 C atoms, it being possible for one or more CH2 groups to be replaced by -O-, -S-, -CO-, -CO-O-, -O-CO- or -O-CO-O- in such a manner that oxygen atoms are not linked to one another, or R2 has the meaning given for R1, and m is 1, and n is 0 or 1.

2. Binaphthol derivatives according to Claim I, in which MG1 and MG2 are independently

with L being OH3, -COCH3, -CN, F or Cl and r being 0, 1 or 2.

3. Binaphthol derivatives according to Claims 1 or 2 characterized in that the groups X1-MG1-Y1-Sp1-R1 and X2-MG2-Y2-Sp2-R2 are identical.

4. Binaphthol derivatives according to any of the preceding claims characterized in that X1 is CO, y1 is -O-, Spi is -(CH2)k- with k being an integer between 2 and 12, and Rt is CH2CW-COO5. A liquid crystalline material in the form of cholesteric polymer network, wherein the polymerized material is obtainable by copolymerization of a achiral compound (a) having one or two polymerizable functional groups and a chiral polymerizable compound (b), characterized in that (b) is a binaphthol derivative of formula I.

6. A liquid crystalline material as claimed in Claim 5, characterized in that the compound (a) is a mesogenic compound or a mixture thereof having one or two polymerizable groups comprising mesogen containing structure elements said mesogens having two side chains attached thereto, at least one of which contains a bifunctional group at the end thereof, wherein said mesogens and said functional groups are separated by at least one to eighteen spacer atoms.

A liquid crystalline material as claimed in Claim 6, characterized in that at least one of the the compounds (a) are a bisacrylate of formula II R3[(CH2)p-A]q-MG3[A-(CH2)p]q-R3 II wherein R is H, CH3 or Cl, A is -O-, -CO-O-, -O-CO- or a single bond, R3 has the meaning given for RI, p and q are integers between 0 and 20, and MG3 has the meaning given for MG1 Amendments to the claims have been filed as follows 1.Chiral polymerizable binaphthol derivatives of formula I

in which A is R-(+)- or S-(-)-1 ,1'-binaphthyl-2,2'-diyl X1 and X2 each independently denote -CO-, -CH2-, or a single bond MG1 and MG2 each independently denote a mesogenic group comprising 1 to 4 ring systems and optionally up to 3 bridging groups y1 and Y2 are each independently -O-, -CO-O-, -O-CO- or a single bond Sp1 and Sp2 are each independently spacer groups with up to 20 C, 0, and N atoms R1 is a polymerizable group selected from the formulae CH2=CW-CO- o-,

HWN-,CH2=CH-, CH2=CH-O- or HS-(CH2)m-COO- with W being H, CI or alkyl with 1-5 C atoms and m being 1-7, R2 is an optionally halogenated alkyl radical with up to 15 C atoms, it being possible for one or more CH2 groups to be replaced by -O-, -S-, -CO-, -CO-O-, -O-CO- or -O-CO-O- in such a manner that oxygen atoms are not linked to one another, or R2 has the meaning given for R1, and m is 1, and n isOor1.

2. Binaphthol derivatives according to Claim 1, in which MG1 and MG2 are independently

with L being CH3, -COCH3, -CN, F or Cl and r being 0, 1 or 2.

3. Binaphthol derivatives according to Claims 1 or 2 characterized in that the groups X1-MG1-Y1-Spl-RI and X2-MG2-Y2-Sp2-R2 are identical.

4. Binaphthol derivatives according to any of the preceding claims characterized in that X1 is CO, Y1 is -O-, Sp1 is -(CH2),- with k being an integer between 2 and 12, and Ri is CH2=CW-COO-

5. A liquid crystalline material in the form of cholesteric polymer network, wherein the polymerized material is obtainable by copolymerization of an achiral compound (a) having one or two polymerizable functional groups and a chiral polymerizable compound (b), characterized in that (b) is a binaphthol derivative of formula I.

6. A liquid crystalline material as claimed in Claim 5, characterized in that the compound (a) is a mesogenic compound or a mixture thereof having one or two polymerizable groups comprising mesogen containing structure elements said mesogens having two side chains attached thereto, at least one of which contains a functional group at the end thereof, wherein said mesogens and said functional groups are separated by at least one to eighteen spacer atoms.

7. A liquid crystalline material as claimed in Claim 6, characterized in that at least one of the compounds (a) are a bisacrylate of formula II R3[(CH2)p-A]q-MG3[A-(CH2)p]q-R3 II wherein A is -O-, -CO-O-, -O-CO- or a single bond, R3 has the meaning given for R1, p and q are integers between 0 and 20, and MG3 has the meaning given for MGx