GB2205845A - Chiral, soluble polydiacetylenes - Google Patents

Abstract

Chiral, soluble polydiacetylenes having at least one chiral centre obtained by polymerising a diacetylene of the general formula: Y-X-(CH2)n-C IDENTICAL C-C IDENTICAL C-(CH2)n-X-Y wherein Y = any chiral group X = any group which aids solubility n = integer from 1 to about 20 presented together with non-linear optical properties, optical device and waveguides formed from such polydiacetylenes.

Description

Choral, Soluble Diacetylenes This invention relates to chiral, soluble polydiacetylenes.

According to one aspect of the present invention there is provided a polydiacetylene which has at least one chiral centre and is soluble. Preferably the polydiacetylene is obtained by polymerising a diacetylene of the general formula: Y - X - (CH2)n - C = C - C--C - (CH2)n - X - Y wherein Y = any chiral group X = any group which aids solubility n = integer from 1 to about 20 According to another aspect of the present invention there is provided a compound, having non-linear optical properties, comprising a polydiacetylene which has at least one chiral centre and is soluble.Preferably the polydiacetylene is obtained by polymerising a diacetylene of the general formula: Y - X - (CH2) n - C ~ C - C L C - (CH2) n - X - Y wherein Y = any chiral group X = any group which aids solubility n = integer from 1 to about 20 According to a further aspect of the invention there is also provided an optical waveguide comprising a compound having nonlinear optical properties as defined above.

Examples of suitable chiral groups, represented by Y, include:

+ combinations of H, CH3, C2H5, C3H7, Examples of suitable groups which aid solubility, represented by X, include:

The following examples illustrate the invention by showing the preparation of a specific family of diacetylenes with the general formula: i - X - (CH2)a - C-C - C=C - (CH2)n - X - Y wherein

n = 1, 2, 3, 4, 6 and 9 t = R or S chirality where R or S designate opposite handed forms of the chiral substituent. The diacetylenes so produced are polymerised, to obtain a specific family of polydiacetylenes in accordance with the invention.

Example 1 Preparation of 2,4-Hexadiyne-1,6-diol bis(R-(+) Methylbenzylurethane) 1-RMBU A solution of 2,4-hexadiyne-1,6-diol (370mg, 3.36m.mol.), triethylamine (lem3) and dibutyltin bis (2-ethylhexanoate) (100mg) in tetrahydrafuran (locum3) was stirred for 10 minutes at room temperature. A second solution of phenylethylisocyanate (1.Og, 6.8m.mol.) in tetrahydrafuran (5cm3) was then added dropwise over a period of 10 minutes. The reaction mixture was stirred for a further 2 hours at room temperature and then poured into n-pentane (100cm3) and filtered to give the urethane as a white solid. The product was re-crystallised from a mixture of ethanol and water to give white, needle-like crystals.

Yield: 1.02g, 75% Melting point: 1190C Micro analysis: C24 H24 N2 O( requires; C, 71.28; H, 5.94; N, 6.93; 0, 15.84% found; C, 71.13; H, 6.24; N, 6.78% I.R. (KBr): 3350(s), N-H: 2900(s), C-H: 1690(vs), C=O.

Example 2 Preparation of 2,4-Hexadiyne-1,6-diol bis(S-(-) Methylbenzylurethane) 1-SMBU A solution of 2,4-hexadiyne-1,6-diol (1.87g, 17m.mol.), triethylamine (1cam3) and dibutyltin bis (2-ethylhexanoate) (O.lg) in tetrahydrafuran (60cm3) was stirred for 10 minutes at room temperature. A second solution of S-(-)-1-phenylethylisocyanate (5.0g, 34.Om.mol.) in tetrahydrafuran (15 cm) was then added dropwise over a period of 10 minutes. The reaction mixture was stirred for a further 2 hours at room temperature and then poured into n-pentane (200cm3) and filtered to give the urethane as a white solid. The product was re-crystallised from a mixture of ethanol and water to give white, needle-like crystals.

Yield: 5.4 g, 78% Melting point: ll1-112 C Micro analysis: C24 H24 N2 O4 requires; C, 71.28; H, 5.94; N, 6.93; 0, 15.84% found; C, 71.86; H, 6.08; N, 7.0% I.R. (KBr): 3350(s), N-H: 2900(s), C-H: 1690(vs), C=O.

No solid-state polymerisation was observed in 1-RMBU and 1 SMBU either by gamma irradiation or by thermal initiation.

Example 3 Preparation of 3,5-octadiyne-1,8-diol bis (R-(+)methylbenzylurethane) 2-RMBU A solution of 3,5-octadiyne-1,8-diol (2.34g, 17m.mol), triethylamine (2cm3), and dibutyltin bis (2-ethylhexanoate) (O.lg) in tetrahydrofuran (30cm3) was stirred for 10 minutes at room temperature. A second solution of phenylethylisocyanate (5.0g, 34.0m.mol) in tetrahydrofuran (20cm3) was added dropwise over a period of 10 minutes. The reaction mixture was stirred for 2 hours at room temperature and then poured into petroleum ether (40-60 0 C boiling fraction, 500cm3) and filtered to give the urethane as a white solid.The filtrate was concentrated to give further material which was combined with the first crop and re-crystallised from a mixture of acetone and petroleum ether (60-80çC boiling fraction) to give a white powder.

Yield: 6.83g, 93% Melting Point: 115-1160C Micro analysis: C26H2eN204 requires: C, 72.22; H, 6.48; N, 6.58; 0, 14.81 % found: C, 72.11; H, 6.64; N, 6.70 X I.R. (KBr) : 3385(s), N-H: 2900(w), C-H: 1705(s), C=O Example 4 Preparation of 3,5-octadiyne-1,8-diol bis (S-(-)methylbenzylurethane) 2-SMBU The title compound was prepared in a similar way to the compound in Example 3 using the following quantities: 3,5octadiyne-1,8-diol (2.34g, 17m.mol)t phenylethylisocyanate (5.Og, 34.0m.mol), triethylamine (2.0cm3), dibutyltin bis (2-ethylhexanoate) (O.lg), tetrahydrofuran (50cml).

Yield: 7.03g, 95% Melting Point: 1160 C Micro analysis: C26H2sN204 requires; C, 72.22; H, 6.48; N, 6.48; 0, 14.81% found: C, 71.86; H, 6.48; N, 6.62 % I.R. (KBr): 3380(s), N-H: 2900(w), C-H: 1700 (s), C=O Example 5 Preparation of 4,6-Decadiyne-1,10-diol bis (R-(+) Methylbenzylurethane) 3-RMBU The title compound was prepared in a similar way to the compound in Example 3 using the following quantities: 4,6decadiyne-1,10-diol (2.56g, 1Sm.mol.), phenylethylisocyanate (5.11g, 34m.mol.), triethylamine (2cm3), dibutyltin bis (2-ethylhexanoate) (O.lg), tetrahydrafuran (25cm3).

Yield: 7.0 g, 98% Melting Point: 110-1120C Micro analysis: C28 H32 N2 04 requires: C, 73.04; H, 6.96; N, 6.09 found: C, 73.09; H, 7.12; N, 6.4/X I.R. (kBr): 33D0(s), N-H: 2900(s), C-H: 1690(vs), C=O.

Example 6 Preparation of 4,6-Decadiyne-1,10-diol bis (S-(-) Methylbenzylurethane) 3-SMBU The title compound was prepared in a similar way to the compound in Example 3 using the following quantities: 4,6 decadiyne-1,10-diol (l.Og, 6m.mol.), phenylethylisocyanate (2.0g, 13.6m.mol.), triethylamine (0.5cm3), dibutyltin bis (2-ethylhexanoate) (O.lg), tetrahydrafuran (5cm).

Yield: 2.5 g, 90% Melting Point: 117-1180C Micro analysis: C2S H32 N2 0o requires: C, 73.04; H, 6.96; N, 6.09% found: C, 73.24; H, 7.11; N, 6.42% I.R. (KBr): 3350(s), N-H: 2900(s), C-H: 1690(vs), C=O.

Example 7 Preparation of 5,7-Decadiyne-1,12-diol bis (R-(+) Methylbenzylurethane) 4-RMBU The title compound was prepared in a similar way to the compound in Example 3 using the following quantities: 5,7decadiyne-1,12-diol (1.3g, 6.7m.mol.), phenylethylisocyanate (2.1lg, 14.3m.mol.), triethylamine (1.3cm3), dibutyltin bis (2-ethylhexanoate) (O.lg), tetrahydrafuran (30 cm1).

Yield: 1.31 g, 40% Melting Point: 72-730C Micro analysis: C30 H36 Nt 04 requires; C, 73.70; H, 7.53; N, 5.91% found; C, 73.77; H, 7.37; N, 5.74% I.R. (KBr): 3350(s), N-H: 2900(s), C-H: 1690(vs), C=O.

Example 8 Preparation of 5,7-Decadiyne-1,12-diol bis (S-(-) Methylbenzylurethane) 4-SMBU The title compound was prepared in a similar way to the compound in Example 3 using the following quantities: 5,7- decadiyne-1,12diol (1.2g, 6.1m.mol.), phenylethylisocyanate (2.0g, 13.6m.mol.), triethylamine (1.0cm3), dibutyltin bis (2-ethylhexanoate) (O.lg), tetrahydrafuran (10cm3).

Yield: 2.8 g, 92% Melting Point: 79-800C Micro analysis: C30 H36 N2 O4 requires; C, 73.70; H, 7.53; N, 5.91% found; C, 73.77; H, 7.37; N, 5.74% I.R. (KBr): 3350(s), N-H: 2900(s), C-H: 1690(vs), C=O.

Example 9 Preparation of 10,12-Docosadiyne-l,22-diol bis(R-(+) Methylbenzylurethane) 9-RMBU A solution of 10,12-docosadiyne-1,22-diol (1.14g, 3.4m.mol.), triethylamine (lcm3), and dibutyltin bis (2ethylhexanotae) (O.lg) in tetrahydrafuran (10cm ) was stirred for 10 minutes at room temperature. A second solution of R-(+)-l- phenylethylisocyanate (1.0g, 68m.mol.) in tetrahydrafuran (5cm3) was added dropwise over 10 minutes.The reaction mixture was stirred for 2 hours at room temperature and then poured into petroleum ether (40 - 60 C boiling fraction, 60cm3) to give further material which was combined with the first crop and re- crystallised from a mixture of acetone and- petroleum ether (tI()= 80 C boiling fraction) to give a white powder.

Yield: 1.49 g, 79% Melting point: 58-60 C Micro analysis: C40 H56 Nz 4 requires; C, 76,43; H, 8.92; N, 4.46 % found; C, 76.26; H, 9.44; N, 3.73 % I.R. (KBr): 3350(s), N-H: 2900(s), C-H: 1690(vs), C=O.

Example 10 Preparation of 10,12-Docosadiyne-l,22-diol bis (S-(-) Methylbenzylurethane) 9-SMBU The title compound was prepared in a similar way to the compound in Example 3 using the following quantities: 10,12docosadiyne-1,22-diol (5.68g, 17m.mol.), phenylethylisocyanate (5.Og, 3m.mol.), triethylamine (1cm3), dibutyltin bis (2-ethylhexanoate) (O.lg), tetrahydrafuran (50cm3).

Yield: 7.5 g, 70% Melting Point: 73-740C Micro analysis: C40 H56 N2 0s requires; C, 76.43; H, 8.92; N, 4.46 % found; C, 76.24; H, 9.05; N, 4.46 % I.R. (HBr): 3350(s), N-H: 2900(s), C-H: 1690(vs), C=O.

Polymerisation of the chiral diacetylenes was obtained by r-ray (60Co) irradiation í450Mrads) of the monomer crystals.

Unreacted monomer was extracted with acetone and the percentage conversion calculated for each monomer.

monomer X Polymerisation 1 -RMBU O 1-SMBU O 2-RMBU 23 2-SMBU 27 3-RMBU 29 3-SMBU 37 4-RMBU 20 4-SMBU 40 9-RMBU 57 9-SMBU 94 Preferably the polydiacetylene is dissolved in a solvent in which it is soluble at room temperature. Preferred solvents for 9-SMBU include chloroform, in which the polydiacetylene is soluble up to a concentration of 10-15% W/W, dichloromethane and 1,2-dichlorobenzene. Poor solvents for 9-SMBU are those in which the polydiacetylene shows low solubility at room temperature and only slightly increased solubility at higher temperatures, these solvents include N,N-dimethylformamide, methyl ethyl ketone and toluene. In general, the other members of the family of polydiacetylenes show similar solubility.

It is well known that the polarisation, P, induced in a material by an electric field, E. can be expressed as: P = #(1). E + #(2) E E + #(3) . E E E + .....

where the vector quantities P and E are related by the tensor co-efficients +'). #(2) and (3). These arise from the polarisability, hyper-polarisability and second hyperpolarisability of the atoms or molecules in the material.

Optically linear materials have very small X and ç#(3)values and the #(1)co-efficient manifests itself as the refractive index.

Optically non-linear materials have large values of ss and 9'3? The first non-linear coefficient, ii,Ll) manifests itself in noncentrosymmetric materials and gives rise to such effects as frequency doubling, frequency mixing, parametric amplification and the linear electro-optic or Pockels effect. The second non linear co-efficient, #(3) , gives rise to such effects as degenerate four-wave mixing, phase conjugation, the Kerr effect and optic bistability. These effects find application in non-linear optical systems.

The compounds suitable for use in non-linear optic systems, hereinafter referred to as NLO, must meet certain requirements of symmetry and electronic structure. For 8 effects the NLO compound must exhibit non-centrosymmetry, both on a molecular and crystal unit cell level. Molecules having at least one chiral centre and which are, therefore, necessarily non-centrosymmetric, may also form crystals in which there is overall non-centrosymmetry in the -unit cell.

In general, the electronic state required for a NLO compound is a polarisable, conjugated pi-electron system. The molecules of diacetylene exhibit such electronic polarisation. However, most diacetylenes crystallise into centrosymmetric phases.

The chirality present in the substituent groups in the compound of formula I, represented by Y, mean that it is possible to isolate polymerisable crystalline phases containing the chiral molecules: R - C-C - CC - R and S - C # C - C # C - S Chiral polydiacetylene phases are produced from these noncentrosymmetric crystal phases and are of interest due to the effects of the chiral substituents on the non-linear optical properties of the polymer.

The chiral polydiacetylenes, according to the invention, are Soluble. This solubility facilitates handling of these compounds and the optic effects of these polydiacetylenes in solution is of interest. They display chromic shifts both as a function of solvent quality (solvatochromism), and temperature (thermochromism). In preferred solvents and at elevated temperatures, the solutions are yellow with peak absorbances near 460nm. In poor solvents or at lower temperatures large bathochromic shifts of the maxima occur. In the chiral polydiacetylenes of this invention these shifts are accompanied by large changes in the chiroptical properties.The conformation of the polymers which gives rise to the optical absorption peak at approximately 450-460nm, i.e. the 'yellow' form, shows no circular dichromism (C.D.), but large C.D. signals are observed for the longer wavelength absorbing. forms of the polymer. These changes render the chiral polydiacetylenes suitable for NLO devices, which utilise the state of polarisation of a light beam of appropriate wavelength.

The conformations of the polymers, which give rise to absorption maxima in the range 500 to 700nm, are the principal component In solutions a) of mixtures of preferred and poor solvents containing more than a critical fraction of poor solvent and b) of pure solvent below a critical temperature. Typical critical compositions for chloroform hexane mixtures are for 9R and 9S 75 mole% chloroform 25 mole% hexane and for 4S 65 mole% chloroform and 35 mole % hexane. In chloroform solutions of 3R the ordered form occurs below 550C. The ordered form of the polymer has a helical or twisted backbone as evidenced by the occurrence of circular dichromism.

Solutions containing high proportions of the ordered form of the polymers can be utilised in applications using electric field induced orientation effects, e.g. electric field induced birefringence for optical switches, and second harmonic generation.

The polymer solutions can be used to fabricate thin film optical waveguides by employing solvent casting, spin coating, substrate withdrawal and other techniques known to those skilled in the art. The solid films of these polydiacetylenes possess large third-order optical nonlinearities and act as low loss optical waveguides. These waveguides can be utilised on their own or in combination with layers of other inactive polymers, for example, polymethylmethacrylate, polystyrene, polyvinyl alcohol and other amorphous polymers soluble in solvents which do not dissolve the polydiacetylenes, to fabricate NLO devices such as NLO couplers, bistable waveguides and other novel NLO systems.

Films formed from the chiral polydiacetylenes of this invention can also be utilised for NLO devices in which the radiation does not propagate in the plane of the film, for example self-defocusing systems for laser protection.

The excellent mechanical properties of the films of these polydiacetylenes allow them to be removed from substrates used in their formation and as free standing films.

Specifically tailored organic materials comprising the soluble polydiacetylene molecules each containing at least one chiral group may, therefore, be designed for the requirements of a particular NLO system.

Claims (14)

CLAIMS:

1. A polydiacetylene which has at least one chiral centre and is soluble.

2. A polydiacetylene according to Claim 1 which has non-linear optical properties.

3. A polydiacetylene according to Claim 1 or 2 wherein the polydiacetylene has a non-centrosymmetric unit cell.

4. A polydiacetylene according to Claim 1, 2 or 3 wherein the polydiacetylene is obtained by substantially polymerising a diacetylene of the general formula: Y - X - (CH )n - C C - C C - (CH2 )n - X - Y wherein Y = any chiral group X = any group which aids solubility n = integer from 1 to about 20

5. An optical device including a polydiacetylene which has at least one chiral centre and is soluble.

6. An optical device according to claim 5 wherein the polydiacetylene has non-linear optical properties.

7. An optical device according to claim 5 or 6 wherein the polydiacetylene has a non-centrosymmetric unit cell.

8. An optical device according to any one of claims 5 to 7 wherein the optical device further includes a polymer having linear optical properties.

9. An optical device according to any one of claims 5 to 8 wherein the polydiacetylene is in the form of a film.

10. An optical device according to any one of claims 5 to 9 wherein the polydiacetylene is obtained by substantially polymerising a diacetylene of the general formula: Y - X - (OH2 )n - CZ-o - C-C - (CH2 ) - X - Y wherein Y = any chiral group X = any group which aids solubility n = integer from 1 to about 20

11. An optical waveguide comprising a polydiacetylene as claimed in any one of claims 1 to 4.

12. A polydiacetylene substantially as hereinbefore described with reference to the Examples.

13. An optical device substantially as hereinbefore described.

14. An optical waveguide substantially as hereinbefore described with reference to the Examples.