WO1995009193A1

WO1995009193A1 - Polymers formed from bis (2,3-dihydroindole-2,3-dione) compounds

Info

Publication number: WO1995009193A1
Application number: PCT/AU1994/000589
Authority: WO
Inventors: Ezio Rizzardo; Caroline Roberts
Original assignee: Commonwealth Scientific And Industrial Research Organisation
Priority date: 1993-09-30
Filing date: 1994-09-30
Publication date: 1995-04-06

Abstract

Polymers formed from bis (2,3-dihydroindole-2,3-dione) compounds and processes for the formation thereof. Polymers having the formula (1) are claimed.

Description

Polymers formed from bis (2,3-dihydroindole-2, 3- dione) compounds

The present invention relates to polymers formed from bis (23-dihydroindole-2 -dione) compounds and processes for the formation thereof.

Biphasic soft/hard segmented polymers and in particular thermoplastic elastomers, have been the subject of much research in recent years. Enhanced mechanical properties are conferred onto the material by phase separation of the soft and hard segments. The hard segment acts as a crosslinking junction point and as a filler. This leads to high strength materials which are also flexible and impact absorbing. Polyurethane elastomers are an example of this class of compounds, where the soft segment is a flexible oligomeric chain e.g. polyether and the hard segment comprises several aromatic rings in close proximity. These aromatic segments are incompatible with the adjacent polyether and aggregate to form a microphase separated morphology. Intermolecular hydrogen bonding between hard segments also contributes towards an aggregated morphology.

However, the synthesis of polyurethanes normally requires the use of diisocyanates as monomers. These compounds have significant health and safety risks. They are known to be extremely destructive to tissue, cause allergic reaction and burning and, in cases of inhalation, can be fatal.

l, -(oxalyl)bis(23-*dihydroindole-2-3-dione) of formula (A)

has been synthesised previously. This compound was reported to undergo nucleophilic attack at the heterocyclic amide carbonyls resulting in cleavage of the nitrogen - carbon bond. Ring opened keto compounds are formed. Glycoxylic esters and glycoxylic amides were synthesised via nucleophilic attack by alcohols and amines, respectively.

It will be appreciated that compound A may be substituted with groups that do not affect the above ring opening reaction to give compounds of formula (B):

It has now been recognised that polymeric materials may be synthesised when bifunctional nucleophilic reagents are employed. l,l'-(oxalyl)bis(23- dihydroindole-23-dione) and derivatives thereof have been found to be a useful linker for macrodiols and macrodiamines to produce polymers with phase separated morphology and elastomeric behaviour.

The present inventors have recognised that the reaction between an oligomeric difunctional nucleophilic reagent and compounds of general formula (B) will lead to novel polymeric materials with useful properties. A polymer is taken to include any species from oligomeric material through to unlimited high molecular weight material.

Therefore, according to the present invention there is provided a polymer having the formula (1)

wherein Y is O or NR₃ x is an integer from 1 to 1000,

R² is alkylene, arylene, alkenylene, silylene, siloxene, sulfoxene, or an oligomeric or polymeric residue; and

R³ is hydrogen, optionally substituted alkyl or optionally substituted aryl; R₄ to R_π may be the same or different and are selected from hydrogen, alkyl, halo, alkoxy, nitro, acyl and amido.

The process for forming the novel polymers of the present invention may be summarised as follows:

(3) Polymers having formulae (2) and (3) are also novel and form part of the present invention.

When the diol HOR²OH or the diamine (NHR³)R²(NHR³) is an oligomeric or polymeric residue it may be selected from any oligomer or polymer known in the field of polyurethane chemistry as co-reactants with diisocyanates, such as polyethers, polyesters, polysiloxanes, polyether esters, polysulphones, polyamines or polycarbonates.

In a further aspect, the present invention provides a process for the preparation of polymers of formula (2) comprising reacting a bis (23*-dihydroindole-23-dione) of formula (B), with at least one diamine of formula (4):

(NHR³)R²(NHR³) (4)

where R² and R³ are as defined above.

In another aspect, the present invention provides a process for preparing a polymer of formula (3) comprising reacting a bis(23 dihydroindole 23 dione) of formula (B) with at least one diol of formula (5):

HOR²OH (5)

where R² is stated above.

In yet a further aspect, the present invention provides chain extension processes of polymers of formula (2) or (3), by further diamines, diols or bisindolediones of formula (4), (5) or (B) respectively. Therefore according to the invention there is provided a process as described above comprising the further step of reacting the compound of formula (2) or (3) with one or more compounds selected from bisindolediones of formula (B), diamines of formula (4) or diols of formula (5).

The above processes may take place in bulk (without solvent) or in any suitable solvent in which compounds of formula (1) are at least slightly soluble. Suitable solvents include dimethylsulphoxide, dimethylformamide, benzene, xylene, diihethylacetamide, 1,1,1-trichloroethane and carbon tetrachloride. Aromatic and chlorinated solvents are preferred. A solvent with a low dielectric constant, is also preferred, a dielectric constant in the range 2.2 to 2.4 being most preferred.

Nucleophilic solvents are not preferred as they may interfere with the polymerisation and produce nucleophilic compounds which in turn inhibit polymerisation which may result in difficulty in obtaining a high molecular weight polymer product.

The above reactions may take place in the presence of a suitable catalyst. Suitable catalysts include those used in polyurethane chemistry such as an amine, pyridine, tin II salt or titanium salt. Preferred is stannous octoate.

The reactions may be conducted at any convenient temperature from room temperature to about 200° C.

The polymers of the invention have novel structures with great variety available through the choice of reactants. They are generally elastomers at room temperature. Use of telechelic polyether macrodiols or macrodiamines lead to soft/hard segmented materials with the attendant mechanical properties.

The novel polymers of the invention may be used in synthesis of functionalised polymers and block co-polymers such as thermoplastic elastomers.

The advantages of the processes used to prepare the polymers of the invention include; the low toxicity of the monomer; the ease of the process in that low temperature of approximately 100 °C or less may be used without the need to reduce the pressure of the reaction vessel; the polymers are synthesised from inexpensive and readily available materials; and a wide variety of polymer structures can be prepared by simple variation of the diol/diamines.

The invention will now be described with reference to the following examples and figures. It will be appreciated that the examples and figures are provided for the purpose of illustrating the invention and that they in no way should be seen as limiting the scope of the above description. Figure 1 is a graph of heat capacity dependence on temperature for the polymer of Example 9.

Figure 2 is a graph of bending modulus (E') and tanδ variation with temperature for the polymer of Example 6.

Figure 3 is a graph of load stress versus strain for the polymers of Examples 4, 6 and 7.

The following materials and equipment was used in the examples.

Materials

l,l'-(oxalyl)bis(23-dihydroindole-23*-dione) was synthesised by the method of Black et al. (Black DSC, Moss GI (1987) Aust. J. Chem 40:129). Oxalyl chloride (25 g, 0.2 moles) was added dropwise to a suspension of indoledione (59.2 g, 0.4 moles) and dry pyridine (42 ml) in dry dichloromethane at 0 °C. The vessel was stirred for 2 hours, allowed to warm to 20 °C and stirred for a further 12 hours. A mustard suspension was produced. The product was filtered and washed with dry dichloromethane followed by washing with dry acetonitrile.

Terethane™ 1000 diol was supplied by DuPont and dried at 100 °C under reduced pressure. A hydroxy determination using the method of ASTM D2849 found a molecular weight of 1010. 0,0'-Bis-(2-aminopropyl)-polyethyleneglycol 1900 (M_n - 2000) was obtained from Fluka, dried at 100 °C under reduced pressure. M_n = 1900 (by GPC), M_n = 1200, n=24 (by NMR).

Stannous octoate was obtained from Aldrich, used as received.

Xylene (o-m,p) - (Pronalys Grade, M&B) An azeotrope of water and solvent (10%) was removed by distillation before use.

Carbon tetrachloride - An azeotrope of water and solvent (10%) was removed by distillation before use.

1,1,1-Trichloroethane - An azeotrope of water and solvent (10%) was removed by distillation before use.

Equipment

A Bruker AC200MHz nuclear magnetic resonance spectrometer was used to collect the NMR data with residual protonated solvent as an internal standard. Chemical Shifts are quoted relative to tetramethylsilane. Molecular weight data was obtained by gel permeation chromatography on a Waters 150C system with six ultrastyragel columns (100, 500, lxlO³, lxlO⁴, 1x10^s, and lxlO⁶ A) with distilled tetrahydrofuran at 30 °C as eluant.

The differential scanning calorimetric data was collected on a Mettler

DSC30 Instrument using a glass sensor over the temperature range -150 °C to 150 °C. A Mettler DSC25 instrument was used for high temperature region, 25 °C to 200 °C. A heating rate of 10 degrees per minute and a flow of nitrogen over the sample were used in both cases. The samples were referenced to an empty pan. The Dynamic Mechanical Analysis was performed on a Polymer

Laboratories Mechanical Analyser with mark 2 low temperature head. The sample was mounted in the dual cantilever mode using an O clamp frame with a G clamp. The sample was mounted with a free path length of 1 mm, heated at a rate of 2 degrees per minute and subjected to frequencies of 1, 5 and 10 Hertz over the temperature range -100 °C to 70 °C. A -log k value of 3.667 was employed. Tensile properties were measured on an Instron Tensometer at a controlled temperature of 20 °C. Samples of polymer were formed into a uniform sheet of 0.6 mm thickness using a hot press at 110 °C. Dumbbells (13 mm x 4 mm in the central portion) were then punched out of these sheets. Ten dumbbells were tested to ensure reproducible results.

EXAMPLE 1

Synthesis cfPolyamide oligomer by reaction of NN'-oxalyl bis(2 ) Dihydroindole 2 dione with a-ω-di-(2-amino-propyl) polyethylene glycol

A solution of α-ω-di-(2-amino-propyl) polyethylene glycol in dimethylformamide was added to a solution of oxalyl bisisatin in DMF. The solution was heated at 60 °C and the polymer was recovered by precipitation into water. Proton NMR showed the repeating unit structure to be

-Ηnmr-δ CDCla): 12.65, bs, NH; 8.7, d, aryl; 833, t, aryl; 7.6, t, aryl; 7.17, t, aryl; 3.5, s, OCH₂; 1.2, d, CH₃; 1.05, d, CH₃.

Gel Permeation Chromatography determined the number average molecular weight to be 7,800 and dispersity to be 2.15 relative to polystyrene standards. Differential Scanning Calorimetry was used to study thermal events indicating polymer phase transitions. The glass transition -T_g was found to be - 50 °C with an endotherm at 40 °C and an exotherm at -30 °C indicating melting and crystallization of crystallites, respectively. EXAMPLE 2

Synthesis cf a polyester oligomer by reaction of NN'-σxάtyl bis (2 -→Uhydroindole-2 -dione) with a-ω dihydroxy pόbytetramethylene oxide

The two monomers, α-ω dihydroxy polytetramethylene oxide and oxalyl bisindoledione were mixed together in the melt at 50 °C with 0.5% w/w stannous octoate. The homogenous mixture was then heated at 100 °C for 20 hours. Proton NMR showed the repeating unit to be

-Η nmr-δ(CDCl₃):12.75, bs, NH; 8.85, d, aryl; 7.6-7.8, m, aryl; 7.25, t, aryl; 4.4, bt, CH₂OCO; 335, bs, CH₂; 1.8, m, CH₂CH₂OCO; 1.55, bs, CH₂CH₂0.

Gel Permeation Chromatography showed the number average molecular weight to be 20,900 and the dispersity to be 2.40 relative to polystyrene molecular weight standards.

Differential Scanning C orimetry (DSC) was used to study the thermal events in the polymer matrix. The glass transition was found to be -70 °C and the melting transition, Tm was 86 °C. EXAMPLE 3

Chain Extension cf telechelic bisindoledione polyether oligomer

A quantitative amount of 1,4 butanediol was added to a solution of bisindoledione terminated oligomeric polyether in tetrahydrofuran. This was refluxed for 3 hours. Polymer was collected and dried to yield a rubbery pale solid. Gel permeation chromatography showed the number average molecular weight to be 16,900 and the polydispersity to be 2.09.

The melting transition was found to be 58 °C by DSC.

^JH nmr-δ(CDCl₃); 12.70, bs, NH; 8.86, d, aryl; 7.70, t, aryl; 7.65, d, aryl; 7.22, t, aryl; 438, t, CH₂OCO; 330, bs, CH₂0; 1.78, m, CH₂ CH₂OCO; 1.58, bs, CH₂ CH₂0.

EXAMPLES 4 TO 9

Synthesis c poly-oxalyl-di-arylene-keto-ester-b o1y(tetrarnethylene oxide)

l,l'(oxalyl)bis(23-dihydroindole-23-dione) was reacted with Terethane™ 100 diol, (a telechelic hydroxy functional polytetramethylene oxide of molecular weight 1000) in the presence of stannous octoate catalyst, to yield the title compound under various reaction conditions as set out in Examples 4 to 9. The physical properties of the polymers produced in Examples 4 to 9 are set out in Tables I to III.

EXAMPLE 4

Poly(tetramethylene oxide) diol 1000 (5 g, 0.005 moles) was mixed thoroughly with l,l'-(oxalyl)bis(23**dihydroindole-23-dione) (1.75 g, 0.005 moles) and stannous octoate (33 mg, 0.5 %w/w) in xylene (40 ml). The oxalyl bis indoledione was insoluble in xylene at room temperature and even at 115 °C was only partially soluble. However, after 2 hours of heating, the solution cleared. The total reaction time was 22 hours. The solvent was removed by distillation under reduced pressure to yield a dark orange solid which was reprecipitated to leave a cream coloured polymer.

EXAMPLE 5

Poly(tetramethylene oxide) diol 1000 (5 g, 0.005 moles) was dissolved in carbon tetrachloride (30 ml). l,l'-(oxalyl)bis(23-dihydroindole-23-dione) (1.75 g, 0.005 moles) and stannous octoate (100 mg, 0.15 %w/w) were added. A yellow suspension was formed. Qxalyl bisindoledione was only partially soluble in carbon tetrachloride even at elevated temperatures. The suspension was heated at reflux for 24 hours. During this period the bisindoledione in solution has reacted with the diol and formed polymer. The polymer was formed in solution and a clear orange viscous solution resulted. The polymer was recovered through the removal of solvent by distillation under reduced pressure to yield a clear orange solid which was reprecipitated to leave a cream coloured polymer.

EXAMPLE 6

Poly(tetramethylene oxide) diol 1000 (5 g, 0.005 moles) was dissolved in benzene (30 ml). l,l -(oxalyl)bis(23-dihydroindole-23-dione) (1.75 g, 0.005 moles) and stannous octoate (200 mg, 03 %w/w) were added. A yellow suspension was formed. After 18 hours at reflux, a clear orange viscous solution was formed. The solvent was removed by distillation under reduced pressure to yield a solid polymer.

EXAMPLE 7

Poly(tetramethylene oxide) diol 1000 (5 g, 0.005 moles) was dissolved in 1,1,1-trichloroethane (25 ml). l,l'-(oxalyl)bis(23-dihydroindole-23-dione) (1.75 g, 0.005 moles) and stannous octoate (200 mg, 03 %w/w) were added. A yellow suspension was formed. A large increase in viscosity and a change to a transparent homogeneous solution were noted after 5 hours of heating at reflux. The total reaction time was 18 hours. The solvent was removed by distillation under reduced pressure to yield a solid polymer.

EXAMPLE 8

Poly(tetramethylene oxide) diol 1000 (5 grams, 0.005 moles) was mixed thoroughly with l,l'(oxalyl)bis(23-dihydroindole-23-dione) (1.75 grams, 0.005 moles) and stannous octoate (33 mg, 0.5%w/w) was added as a catalyst. This mixture was heated at 100 °C for a total of 21 hours to yield a hard orange material which was reprecipitated to leave a cream coloured polymer.

EXAMPLE 9

Poly(tetramethylene oxide) diol 1000 (5 grams, 0.005 moles) was mixed thoroughly with l,l'(oxalyl)bis(23-dihydroindole-23-dione) (1.75 grams, 0.005 moles) in xylene and stannous octoate (33 mg, 0.5%w/w) was added as a catalyst. This mixture was heated at 100 °C for a total of 21 hours to yield a hard orange material which was reprecipitated to leave a cream coloured polymer.

Results - Examples 8 and 9

¹HNMR-δ[CDCl₃]:12.75, b.s, NH; 8.85, d, aryl; 7.6-7.8, m, aryl; 7.25, t, aryl;

4.40, b.t, CH₂OCO; 335, b.s, ⁽ ^CH^H^H- 1.80, m, CH₂CH₂OCO; 1.55, b.s, OCH₂CH₂CH₂CH₂0. ¹³C NMR - δ[CDCl₃]: 118.5, 121, 124, 133.5, 137, 140.5, aryl; 158.5, 163.5, 189.5, carbonyl; 26, 26.5, 27(major), CH₂CH₂ polyether segment minor signals due to the polyether segment adjacent to the bisindoledione segment; 70, 71 (major), CH₂0 polyether. EXAMPLE 10

Synthesis cfPoty-amlyl-dia-ylene-keto-amide-polyfethylene oxide)

l,l'-(oxalyl)bis(23 dihydroindole-2-3-dione) (0.87 g, 2.5 mmol) and 0,0'- bis-(2-amino-propyl)-polyethylene glycol 1900 (5 g, 2.5 mmol) were mixed and heated at 100 °C for 18 hours to yield the title compound.

*H NMR - δ[CDCl₃]: 12.65, b.s, NH; 8.70, d, aryl; 833, t, aryl; 7.60, t, aryl; 7.17, t, aryl; 3.50, s, OCH₂CH₂O; 120, d, CH,; 1.05, d, CH₃. ^UC NMR - δ[CDCl₃]: 70, CH₂0.

Physical properties of the resulting polymer are set out in Tables I to III.

Table I: Polymer Molecular Weight Data

Molecular weights are relative to polystyrene standards using polystyrene Mark-Houwink coefficients.

Example M_n Mw M_p Mw/M.

4 37350 60,800 54200 1.61

5 18,700 47,100 43200 2.51

6 38,600 79,000 66,700 2.04

7 36,400 75300 60,100 2.07

8 10,900 26300 25200 2.41

9 20,900 50300 42,100 2.40

10 7,800 17200 31200 2.19 Table II: Transition temperatures, determined by DSC at a heating rate of 10°C/min

T _'s are quoted as onset temperatures.

Table HI: Glass transition temperatures and Storage Modulus values determined by DMTA at 10 Hz

Example Sample T_g ( °C) E' at

Thickness 20 ° mm (MPa)

4 0.23 -47 53.2

5 0.23 -36 35.5

6 0.69 -49 50.0

7 0.16 -49 17.7 Phasp Transitions

The DSC trace illustrated in Figure 4 is typical of those obtained for the polyetherpolyketoesters. The glass transitions and the melting transition are immediately apparent. Table II contains the data on phase transitions as seen by DSC for the series of polymers. The glass transition exists far below ambient temperature, indicating that the materials are in the rubber state at room temperature. There is little variation in T_g though that of the polymers of Examples 8 and 9 are 5-6 °C higher than the others. This is due to the less well defined phase separation in these lower molecular weight materials. All T_g's are elevated over that of the poly(tetramethylene oxide) 1000 which appears at -92 °C. This 10-15 °C rise is expected since the mobility of the polyether is limited by the presence of the bisindoledione segments whether phase separated or not.

The melting transition T_m, which is exhibited as an endotherm, ranges from

68 to 80 °C. The polymer of Example 8 exhibits a lower T_m than others due to a weaker clustering caused by the lower molecular weight (M_n = 10,900).

Figure 5 illustrates a typical output from dynamic mechanical analysis of the polyether-polyketoesters and Table III summarises the information. The technique is sensitive to the glass transition and the melting transition. The sample geometry becomes distorted when heated above T_m, this loss of sample dimensional stability makes it impossible to monitor T_m using this method. However, it can be seen that the glass transition is clear and the bending modulus is defined over the entire temperature region. The glass transition was detected at temperatures 40 degrees greater than those found by the calorimetric method. It is well known that the differing test frequencies of the two techniques result in differing transition temperatures. The absolute values of modulus are sensitive to sample geometry. It is believed that the low values of the polymers of Example 5 and 7 are low due to the relative thin samples used in these two cases. However, the results are the same order of magnitude. Tensile Measurements

Figure 6 shows the stress versus strain curves for three polymers. In each case ten samples were run.

These new polyetherpolyketoester materials exhibit tensile strengths of approximately half those of polyurethane elastomers. The polyether-polyketoester materials of Examples 4 to 10 are not chain extended and so are relatively low molecular weight. Commercially available polyurethane elastomers exhibit tensile strengths of 30-50 MPa with molecular weights in the region of 100,000.

Thermal Stability

These poly(tetramethylene oxide)-polyketoesters have been shown to be stable up to temperatures of 150 °C under an inert atmosphere and up to 100 °C under normal atmospheric conditions.

EXAMPLES 11 TO 24

Synthesis cf pofyether-pofyketoesters

1,1 '-(oxalyl)bis(23-dihydroindole-23-dione) was reacted with equimolar amounts of various diols of formula (5) under different reaction conditions to yield polyether-polyketoesters. The diols, reaction conditions and properties of the resultant polymers are listed in Table V. Table V

Example Diol* Solvent Catalyst Temperature- Polymer (3) No. HO-R²-OH Time

H^xHr³ M„xiσ³

11 PTMO 1000 none pyridine 80°C, 18 h 9.8 5.1

12 PTMO 650 DMF triethylamine 100^βC, 2 h 43 2.6

13 PTMO 50 none stannous 120^βC, 5 h 342 12.0 octoate

14 PTMO IOOO none stannous 100^βC, 22 h 213 9.0 octoate

15 PTMO 1000 xylene stannous 115°C, 20 h 22.8 13.6 octoate

16 PT O 1000 acetone stannous 56°C, 20 h 2.9 1.9 octoate

17 PTMO 1000 THF stannous 66°C, 24 h 2.9 2.0 octoate

18 PTMO 1000 dimethyl stannous 50^βC, 24 h 2.6 1.7 acetamide octoate

19 PTMO IOOO none titanium 100°C, 21 h 19.4 9.4 butoxide

20 PT O 400 none stannous 100° C 18 h 15.0 8.8 octoate

21 PEO 1000 none stannous 100^βC, 6 h 21-5 13.0 octoate

22 PTMO 2900 none stannous 100° C, 7 h 38.9 15.4 octoate

23 PTMO IOOO dichloro¬ stannous reflux, 48 h 182 8.7 methane octoate Example Diol* Solvent Catalyst Temperature- Polymer (3) No. HO-R²-OH Time is xiσ³ M-.xiσ³

24 PTMO carbon stannous reflux, 48 h 462 162

1000: tetra¬ octoate

Butanediol chloride

(10:1)

* PTMO 1000 = Poly(tetramethylene oxide) diol of MW 1000. PEO 1000 = Polyethylene oxide) diol of MW 1000.

EXAMPLES 25 TO 30

Synthesis cf potyether-polyketoamides

l,l'-(oxalyl)bis(23-dihydroindole-23-dione) of formula (1) was reacted with equimolar amounts of α, ω-di-(2-aminopropyl)poly(ethylene glycol) of formula (4) of MW 2000 under various reaction conditions. The reaction conditions and properties of the resulting polyether-polyketoamides are listed in Table VI.

Table VI

Example No. Solvent Temperature Time Polymer (2)

H-xlO^'3 M„xl0-³

25 CH₂C1₂ 50 °C 48 h 183 8.7

26 DMF 60 °C 2 h 15.5 6.8

27 DMSO 120 °C l h 16.2 7.1

28 DMF 70 °C 2 h 19.1 7.9

29 DMAc 70 °C 2 h 13.0 63

30 DMF 22 °C 0.5 h 17.5 8.5

Those skilled in the art will appreciate that the invention described herein is subject to modifications and variations other than those specifically described. It is therefore to be understood that the invention includes all such modifications and variations that fall within its spirit and scope.

Claims

CLAIMS:

A polymer or oligomer having the formula (1):

wherein Y is O or NR₃ x is an integer from 1 to 1000,

2. A polymer or oligomer having the formula (2):

wherein x, R², R³ and R⁴ to R¹¹ are as defined in claim 1.

3. A polymer or oligomer having the formula (3):

wherein x, R², R³ and R⁴ to R¹¹ are as defined in claim 1.

4. A polymer or oligomer according to any one of claims 1 to 3 wherein R² is an oligomeric or polymeric residue selected from polyethers, polyesters, polysiloxanes, polyether esters, polysulphones, polyamines and polycarbonates.

5. A process for the preparation of a compound having the formula (2) as defined in claim 2 comprising reacting a bis (23-dihydroindole-23*-dione) of formula (B):

with at least one diamine of formula (4):

(NHR³)R²(NHR³) (4)

where R² and R³ are as defined in claim 1.

6. A process for the preparation of a compound having the formula (3) comprising reacting a bis(23 dihydroindole 23 dione) of formula (B) as defined in claim 5 with at least one diol of formula (5):

HOR²OH (5)

where R² is as defined in claim 1.

7. A process according to claim 5 or claim 6 wherein the process takes place in bulk.

8. A process according to claim 5 or claim 6 wherein the process takes place in a solvent selected from dimethylsulphoxide, dimethylformamide, benzene, xylene, dimethylacetamide, 1,1,1-trichloroethane and carbon tetrachloride.

9. A process according to claim 5 or claim 6 wherein the reaction is conducted in the presence of a catalyst selected from amines, pyridine, tin II salt or titanium salt.

10. A process according to claim 5 or claim 6 comprising the further step of reacting the compound of formula (2) or (3) with one or more compounds selected from bisindolediones of formula (B), diamines of formula (4) or diols of formula (5).