~~~ ~ Synthesis of polyesters containing 9,10-diacetoxyanthracene-2,6=diylmoieties via a precursor polymer approach Ruab Uddin," Philip Hodge,"" Michael S. Chisholmb and Paul Eustaceb "Chemistry Department, University of Manchester, Oxford Road, Manchester, UK M13 9PL bICI Materials, Wilton Research Centre, PO Box 90, Middlesbrough, Cleveland, UK TS90 8JE Soluble polyesters are synthesised by polymerising a range of bis(acid ch1oride)s with the bisphenol that is formally the Diels- Alder adduct of 9,10-diacetoxy-2,6-dihydroxyanthraceneand dimethyl maleate. Heating the soluble polyesters to about 230 "C brought about retro-Diels-Alder reactions to give the insoluble target polyesters containing 9,lO-diacetoxyanthraceneresidues. There is considerable interest in polymers consisting of aro- matic units linked together directly or uiu ester, ketone, ether, thioether, sulfone, amide or imide moieties because they often form the basis of excellent high performance materials.' In many cases these polymers also display liquid crystal proper- ties.2 It can, however, be difficult to synthesise such polymers with a substantial degree of polymerisation due to their poor solubilities.This problem can sometimes be overcome by using a precursor polymer synthetic appr~ach.~ This involves syn- thesising a soluble and therefore easily characterised and processed polymer which under appropriate conditions, for example heating, undergoes a simple chemical transformation to give the target polymer. We are interested in synthesising fully-aromatic polymers containing anthraq~inone-2~6-diyl moieties 1 for several reasons.Firstly, the anthraquinone unit, though stable to high temperatures in air, has interesting chemical reactivity, for example, redox ~hemistry.~ Secondly, we have shown recently that the moiety 1 is mesogenic.' Thirdly, they can be expected 0 OCOCH-, 0 OCOCH, 1 2 to be accessible by a precursor polymer approach based on the Diels-Alder chemistry of anthracenes and thus they are potentially a type of high performance polymer that can be processed easily during synthesis. As part of a programme to investigate polymers containing moieties 1, we have synthesised a series of polyesters containing 9,lO-diacetoxyanthracene moi-eties 2.The results are reported in this paper. The moieties 2 have the potential for easy conversion into moieties 1. Several anthracene-containing polymers have been prepared before.6p12 The previous work that is most relevant to the present work is that reported by a research group at Du Pont.8 They synthesised the series of polyesters 3 via precursor polymers 4, see Scheme 1. As a consequence of the modest solubilities of the precursor polymers the molecular masses were estimated from the inherent viscosities of solutions in a 40 :60 mixture of 1,1,2,2-tetrachloroethaneand phenol. Results and Discussion The work carried out can be conveniently discussed in three parts: the synthesis of a bisphenol monomer incorporating a suitable precursor unit, polymerisations using this monomer to give precursor polyesters, and then conversion of the latter into the target polymers.Synthesis of monomer 9 and related work The initial objective was to synthesise from commercially available 2,6-dihydroxyanthraquinone(5) (anthraflavic acid) a 2,6-bisphenol monomer which was, or was formally, a Diels- Alder adduct of 9,10-diacetoxy-2,6-dihydroxyanthraceneand which would lead to precursor polymers with a significant solubility in a range of organic solvents. 2,6,9,10-Tetraacet- oxyanthracene (6) is the obvious synthetic intermediate and it was prepared in 79% yield by heating the quinone 5 with zinc dust, acetic anhydride and sodium acetate (Scheme 2). 9,lO-Diacetoxyanthracene(10) was prepared from 9,lO-anthra- quinone in a similar manner for use as a model compound.OCOCH, OCOCH3 10 OCOCH3 OCOCH3o$flF qo,cH3CH3COO CH3COO COzCH3 0 11 12 Maleic anhydride, dimethyl fumarate and methyl acrylate, being relatively rea~tive'~ and cheap, were investigated as dienophiles in Diels-Alder reactions with the above tetraace- toxyanthracene. High yields of isolated adduct were obtained only when maleic anhydride was used. This dienophile afforded adduct 7 in 79% yield. The failure of the other dienophiles to react well is consistent with the facts that maleic anhydride is the most reactive of the three dienophiles in the Diels-Alder reactions with 9,lO-dime thylant hracene,I3 and that 9,l O-diace- toxyanthracene (10) is expected to be less reactive in Diels- Alder reactions than anthracene it~e1f.l~ The diacetoxyanthra- cene (10) reacted with maleic anhydride to give Diels-Alder adduct 11.Treatment of adduct 11 with methanol containing 2% of concentrated sulfuric acid at 60 "Cfor 4 h gave what is formally the dimethyl maleate adduct 12 in 71 YOyield. The anthracene- J. Muter. Chem., 1996, 6(4), 527-532 527 where R = -(c€lz)m-(where m = 4 8 or 10) m or p phenylene Scheme 1 9 OCOCH? Zn acetic anhydnde sodium acetate * CH2COO 0 bCOCH3 5 6 maleic anhydnde in xylenei OCOCH3 OCOCH3 CH3COO q-JoCOCH3 CH3COO CH3COO\ C02CH3%H\ and isomer with H LC02H C0,CH3 and CO,H interchanged H 0 8 7 OCOCH3 9 Scheme 2 Synthesis of monomer 9 maleic anhydride adduct is reported to react similarly l5 The product was mainly half methyl ester 8 together with a minor stability of the 9-and 10-acetoxy groups in adduct 11 under amount of the required dimethyl ester 9 It IS not clear why these conditions is expected because they are esters of bridge-groups in the 2-and 6-positions should affect the course of head tertiary alcohols Adduct 7, on the other hand, did not the reactions at the anhydride group Unfortunately, attempts react as cleanly as adduct 11 with methanol and sulfuric acid to drive the reaction between adduct 7 and methanol to As expected the 9-and 10-acetoxy groups were unreactive and completion by using more vigorous conditions also produced the 2-and 6-acetoxy groups were cleanly methanolysed a complex mixture However, treatment of adduct 7 with However, the anhydride moiety reacted only partially and the methanol and sulfuric acid at 20 "Cfor 6 days cleanly gave the 528 J Muter Chern, 1996,6(4), 527-532 half ester 8 in 84% yield.The latter then reacted with ethereal fdiazomethane to give the monomer 9 in 89% yield. The reactions involved in the successful synthesis of mon- omer 9 are summarised in Scheme 2. In simple tests monomer 9 was poorly soluble in diethyl ether and chloroform but it dissolved readily in acetone, tetrahydrofuran, methanol and -R-cl"dimethyl sulfoxide. It also dissolved in an equivalent amount of 1 mol dm-3 aqueous sodium hydroxide and, after the solution had been left at 20 "C for 4h, the monomer could be recovered unchanged upon acidification.Synthesis of precursor polymers The bisphenol monomer 9 was copolymerised using two phase systems. In each case the bis-salt of the bisphenol in water was treated with a solution of the bis(acid chloride) in chloroform. Tetrabutylammonium cations served as phase transfer catalysts and the reactions were carried out for 2 h at 23°C. The precursor polymers were isolated by precipitation into meth- anol and then purified by washing and/or reprecipitation. They were characterised by elemental analysis (C and H), infrared and 'H NMR spectroscopy and GPC. The results are summar- ised in Table 1. The formulae for polymers PP1-PP9 are given in Scheme 3.For the synthesis of precursor polymers PP1 and PP2 procedure A was used. In this procedure equimolar amounts of bisphenol and bis(acid chloride) were used, the bisphenol was dissolved in aqueous sodium hydroxide and tetrabutylam- monium bromide (8 mol%) was added to provide phase trans- fer catalysis. The yields and degrees of polymerisation obtained were not very high and in an attempt to improve these results procedure B was used. In this procedure the bisphenol was neutralised using aqueous tetrabutylammonium hydroxide and no tetrabutylammonium bromide was added. The net effect is that the amount of phase transfer catalyst present was much higher than in procedure A. However, it is clear from the syntheses of precursor polymers PP3 and PP4, see Table 1, that this produced no significant improvement in the degrees of polymerisation.At this stage it was suspected that although the sample of monomer 9 appeared from 'H NMR spec-troscopy and elemental analysis to be of high purity, the purity may not in fact be very high. In procedure C, therefore, the amount of phase transfer catalyst present was kept high but the bisphenol monomer was used in a small excess (5 mol%). Using this procedure precursor polymers PP5-PP9 were pre- pared in high chemical yields and with average degrees of polymerisation in the range of from 35 to 190. All the precursor polymers obtained were soluble in chloro- form, tetrahydrofuran, N,N-dimethylformamide and dimethyl sulfoxide. Good clear films could be cast from chloroform PP1-PP9 I iheat OCOCH3 J" FP1-FP9 where PP1, FP1 R = -(CH 218-R= -+PP2, FP2 3PP3, FP3 R= PP4, FP4 R= PP5, FP5 R = -(CH2)4-PP6, FP6 PP7, FP7 PP8, FP8 PP9, FP9 Scheme 3 solutions.By differential scanning calorimetry (DSC) all the polymers were stable up to about 210"C, above which the retro-Diels-Alder reactions began to occur (see Table 2). Only precursor polymers PP1 and PP5 showed glass transition temperatures below the decomposition temperatures. The former had Tg = 121"C and the latter Tg = 179 "C. Table 1 Synthesis of precursor polyesters using monomer 9" molecular mass x polymer bis(acid chloride) procedure" yield (Yo) Mn Mw polydispersity degree of polymerisation PPl 78 18.8 41.8 2.2 59 PP2 75 4.5 11.0 2.5 15 PP3 90 5.2 13.0 2.5 17 PP4 77 3.5 6.2 1.8 12 PP5 87 12.2 23.8 2.0 35 PP6 98 43.7 82.0 1.9 122 PP7 97 20.2 52.6 2.6 52 PP8 C 99 49.7 140.0 2.8 124 PP9 ClOC mcoclC 98 72.5 174.2 1.9 190 a See Experimental section for details of method.Estimated by GPC. System calibrated using polystyrene standards. J. Mater. Chem., 1996, 6(4), 527-532 529 Table 2 Conversion of precursor polymers to final polymers and some propeties of the latter elemental analysis (%) precursor polymer final polymer TonsetloC' DSC TGA weight loss in TGA % calc YOfound A,,, of final polymerb/nm calc C found calc H found Gec/'Cc PPl FP1 214 220 23 29 337, 357, 378, 399 683 703 57 52 249 PP2 FP2 226 210 24 27 -357, 379,400 - - - - - PP3 FP3 239 229 24 26 337, 359, 379,400 684 674 35 36 - PP4 FP4 229 214 24 22 338, 359, 379, 399 684 672 35 37 - PP5 FP5 223 216 25 30 336, 357, 378, 399 661 672 46 44 249 PP6 FP6 231 210 24 27 684 673 35 36 289 PP7 FP7 247 210 21 26 380, 400 722 720 38 37 - PP8 FP8 252 231 21 25 340, 359, 379, 401 701 705 36 36 284 PP9 FP9 251 245 22 28 379, 401 711 711 36 35 27 1 TOnset=Temperatureof onset of decomposition Sample heated at 10°C min-' New absorption maxima Polymer PP9, for example, displayed A,,,/nm 342 and 356 prior to heating, due to the presence of naphthalene residues 'By DSC Conversionof precursor polymers into final polymers Heating the precursor polymers was expected to bring about retro-Diels-Alder reactions with the formation of the target polymers and the elimination of dimethyl maleate This was monitored using DSC and TGA As estimated by DSC, in the solid state the simple 9,lO-diacetoxyanthraceneadducts 11 and 12 undergo the retro-Diels-Alder reaction at 240 "C and 212 "C respectively Consistent with this it was shown by DSC that with precursor polymers PP1-PP9 the temperatures for the onset of the decompositions were in the range 214 "C to 252 "C The Du Pont researchers found that precursor polymers 4 were converted into polymers 3 at 200-300 "C The decompo- sitions of precursor polymers PP1-PP9 were also monitored by thermogravimetric analysis (TGA) As the temperatures of the samples were increased, the samples began to lose weight at temperatures in the range 210-245 "C and when this loss of weight ceased in each case the total weight loss was close to that expected for the retro-Diels-Alder reaction, see Table 2 The decompositions were also studied using UV spec-troscopy For this purpose films of the precursor polymers were cast on quartz from solutions in chloroform The films were clear and colourless After measurement of their UV spectra, the samples were heated in a vacuum oven (<1 mm of Hg) at 200 "C for 2 days The spectra were then remeasured It was found that whereas the original films showed no absorption in the 325-400nm region, after heating the films showed typical anthracene-type adsorption The Amax of the absorptions are given in Table 2 and typical spectra are shown in Fig 1 75 275 300 3SO 400 450 A /nm Fig.1 Ultraviolet spectra of precursor polyester PP5 before heating (trace 1) and after heating (trace 2) for 46 h The product is final polymer FP5 530 J Muter Chem, 1996, 6(4), 527-532 In several cases larger samples of film were prepared and the film broken up to provide samples for the measurement of infrared spectra and for elemental analyses The infrared spectra were significantly different from those of the precursor polymers, in particular the carbonyl bands due to the 9- and 10-acetoxy groups shifted from ca 1745 cm-I to ca 1780 cm-' Given the method used to prepare the samples, for example, that the films may have contained traces of dimethyl maleate, the results of the analyses (see Table 2) were reasonably close to the theoretical values Finally, it was noted that after heating to bring about the retro-Diels-Alder reactions, though the films remained clear and transparent they became pale yellow to brown in colour, suggesting some thermal decomposition Measurement of decomposition temperatures by DSC indicated, see Table 2, that decomposition generally begins at temperatures in the range 249-284°C Thus, there is a relatively narrow tempera- ture range over which the retro-Diels-Alder reactions can be effected satisfactorily Conclusions Precursor monomer 9 was synthesised from commercially available 2,6-dihydroxyanthraquinone 5 The monomer 9 was polymerised in two phase systems with a range of bis(acid ch1oride)s This gave the soluble precursor polyesters PP1-PP9, see Scheme 3 Heating the precursor polymers at ca 230 "C brought about retro-Diels-Alder reactions and the formation of the target polyesters FPl-FP9 which contain 9,10-diacetoxyanthracene moieties 2 It is of interest to note that the 9- and 10-acetoxy groups and the two methoxycar- bony1 groups in monomer 5 survive the polymerisation con- ditions Future work will attempt to use monomer 9, or close relatives, to synthesise polyethers Experimental Melting points were determined using an Electrothermal 9100 apparatus and are uncorrected Infrared spectra were recorded using a Perkin-Elmer FT-IR 1710 instrument and, except where stated otherwise, were measured as KBr discs Ultraviolet spectra were recorded using a Shimadzu UV 260 instrument 'H NMR spectra were recorded for solutions in deuteriochloroform using either a Varian Gemini 200 or a Varian Unity 500 instrument J Values are given inHz Elemental analyses were obtained from the Departmental Microanalysis Service using a Carlo Erba 1108 Elemental Analyser Gel permeation chromatography (GPC) measure- ments were carried out using 02% (w/v) solutions in tetca- hydrofuran, 4 p Styragel columns ( lo6, lo4, lo3 and 500 A), tetrahydrofuran as the eluent and a Waters 410 differential refractometer as the detector.Polystyrene standards provided the molecular weight calibration. Differential scanning calor- imetry (DSC) and thermogravimetric analysis (TGA) were carried out on samples of 5-10mg using a Seiko 220C dual purpose instrument. Sealed aluminium cells were used for DSC and open pans were used for TGA. Both were performed under an atmosphere of nitrogen with a heating rate of 10 "C min- '. Conversion of 2,6-dihydroxyanthraquinone(5) into 2,6,9,10- tetraacetoxyanthracene (6) 2,6-Dihydroxyanthraquinone ( 10.00g, 41.7 mmol), sodium acetate (8.00g, 97.7 mmol) and zinc powder (6.04 g, 92.4 mmol) were placed in a round-bottom flask. Acetic anhydride (200 ml) was added and the mixture stirred. After the exotherm subsided the mixture was vigorously stirred and heated under reflux for 5 h.As the mixture was cooled, a pale green solid precipitated. A few drops of concentrated sulfuric acid were added to destroy unchanged zinc powder. The mixture was then poured onto ice-water (1200 ml) and stirred for 2 h. The solid product was filtered off, washed with a small amount of cold ethanol and then recrystallised from acetic acid. This gave the required product 6 (10.26 g, 79% yield), mp, 281-283 "C, (lit.,I6 274 "C); vmax(Nujol rnull)/cm-l 1753; SH 2.38 (6 H; s 2-and 6-OCOCH,), 2.63 (6 H; s 9-and 10-OCOCH,), 7.30 (2 H, d, J 9.0 and 1.5, 3- and 7-H), 7.60 (2 H, d, J= 1.5, 1- and 5-H) and 7.93 (2H, d, J 9.0, 4- and 8-H) (Found: C, 64.9; H, 4.1. Calc. for C22Hl'O': C, 64.4; H, 4.1%).9,lO-Diacetoxyanthracene(10) This compound was prepared from anthraquinone using the procedure given above. 9,lO-Diacetoxyanthracene (10) was obtained in 83% yield, mp 279-280 "C (from acetic acid) (lit.,17 264-266'C); vmax/cm-' 1750; 6, 2.65 (6H, s, 9-and 10-OCOCH,), 7.55 (4H, 2-, 3-, 6- and 7-H) and 7.96 (4H, m, 1-, 4-, 5- and 8-H). DielsAlder adduct 7 from compound 6 and maleic anhydride A mixture of 2,6,9,10-tetraacetoxyanthracene (6) (1.42 g, 3.5 mmol) and maleic anhydride (0.68 g, 6.9 mmol) in p-xylene (30 ml) was heated at reflux temperature for 4 days. The mixture was cooled then the pale brown solid which formed was filtered off and dried. Recrystallisation from chloroform gave the adduct 7 (1.39 g, 79%) as white crystals, mp 234-236 "C; vmax(Nujol mull)/cm-' 1865 and 1786 (anhydride C=O) and 1762 (ester C=O); 6, 2.27 (3 H, s, 2-OCOCH3), 2.29 (3 H, s, 6-OCOCH3), 2.54 (6 H, s, 9-and 10-OCOCH,), 5.12 (2 H; s, bridge C-H), 6.95 (1 H, d, J 1.5, 1-H),6.98 (1 H; q, J 8.7 and 1.5, 3-H), 7.10 (1 H; q, J 9.2 and 2.3, 7-H), 7.20 (1 H, d, J 8.7, 4-H), 7.38 (1 H, d, J 2.3, 5-H) and 7.62 (1 H, d, J 9.2, 8-H) (Found: C, 61.0; H, 3.9.Calc. for C26H20011:C, 61.4; H, 3.9%). DielsAlder adduct 11 from 9,lO-diacetoxyanthracene10 and maleic anhydride A mixture of 9,lO-diacetoxyanthracene(10)(2.94 g, 10.0 mmol) and maleic anhydride (1.30 g, 13.3mmol) in p-xylene (25 ml) was heated at reflux temperature for 3 days. An off-white solid formed.It was collected and then recrystallised from chloro- form to give the adduct 11 (3.07 g, 83%), mp 255-257 "C, vmax/cm-1868m and 1786s (5-membered ring anhydride) and 1738s (ester carbonyl); 6, 2.58 (6 H, s, 9-and 10-OCOCH,), 5.14 (2 H, s, bridge C-H), 7.1-7.4 (6 H, m, 1--4-and 6-and 7-H) and 7.64 (2 H, m, 5-and 8-H) Found: C, 67.3; H, 4.2. Calc. for C22H1,07: C, 67.3; H, 4.1%). Reaction of adduct 11 with methanol A mixture of adduct 11 (3.00 g, 7.7 mmol) and acidic methanol (75 ml, containing 2% of concentrated sulfuric acid) was heated under reflux. Initially adduct 11 was insoluble but it slowly dissolved as it reacted. After 2 days most of the solvent was evaporated off under reduced pressure and the slurry so obtained was treated with water (50 ml).The precipitate which formed was collected, washed with copious amounts of water and dried. This gave compound 12 (2.38 g, 71%) as a white solid, mp 196-198 "C; vmax/cm-' 1755; 6, 2.45 (6 H, s, 9-and 10-OCOCH,), 3.50 (6 H, s, 2 x CO,CH,), 4.65 (2 H, s, bridge C-H), 7.20 and 7.60 (8 H, m, 8 x ArH) (Found: C, 65.5; H, 5.2. Calc. for C24H2208:C, 65.8; H, 5.0%). Reaction of adduct 7 with methanol (a)Adduct 7 (2.00 g, 3.9 mmol) was treated with acidic meth- anol (35 ml, containing 2% of concentrated sulfuric acid) at reflux temperature for 24h. Most of the solvent was then evaporated off under reduced pressure, a mixture of water and methanol (1 :1, 30 ml) was added, and the pH was adjusted to 7 using dilute aqueous sodium hydroxide.The product was then extracted with ethyl acetate (30 ml x 3). The combined extracts were dried (magnesium sulfate) and evaporated to dryness (0.43 g, ca. 23%). Analysis by 'H NMR spectroscopy in comparison with the spectrum (see below) of an authentic sample of monomer 9 indicated that whilst the product was mainly monomer 9 it contained substantial impurities. Presumably the main product was half acid 8 and this formed the sodium salt of the acid at the time the pH was adjusted. (b) Adduct 7 (8.00 g, 15.7mmol) was treated with acidic methanol (60 ml, containing 1% of concentrated sulfuric acid) at 20°C for 6 days. A clear solution eventually formed. Most of the solvent was evaporated off under reduced pressure and the residue was added to ice-cold water (100 ml).A precipitate formed which was collected, washed with water and dried. This gave half acid 8 (6.03 g, 84%) which decomposed without melting at ca. 190 "C; v,,,(evaporated film)/cm-' 3402s, br (carboxylic acid 0-H stretch) and 1745s, br (C=O stretch of 3 ester groups and 1 carboxylic acid group); 8, 2.30 (6 H, s, 9-and 10-OCOCH,), 3.45 (3 H, s, C02CH3), 4.45 (2 H, s, 2 x bridgehead C-H), 6.50-7.25 (6 H, m, 6 x Ar-H) Found: C, 60.1; H, 5.0. Calc. for C23H22010: C, 60.3; H, 4.8%). Methylation of compound 8 using diazomethane A solution of compound 8 (2.00 g, 4.4 mmol) in tetrahydro- furan (30 ml) was treated with ethereal diazomethane (pre- pared'' from N-methyl-N-nitrosotoluene-p-sulfonamide)until the yellow colouration persisted. The excess of diazomethane was then destroyed by the addition of a few drops of acetic acid.Most of the solvent was removed under reduced pressure and the residue added to diethyl ether. The precipitate was collected and recrystallised from a mixture of tetrahydrofuran and hexane. This gave monomer 9 (1.83g, 890/), which decom- poses without melting at ca. 220"C, vmaX/cm-' 3401 m, br (OH)and 1746s,br (OCOCH, and C02CH3 C=O); 6,(C2H6]-DMSO) 2.35 (6 H, s, 9-and 10-OCOCH,), 3.38 (6 H, s, 2 xC02CH,), 4.40 (2 H, s, bridgehead C-H) and 6.5-7.3 (6 H, m, ArH) (Found: C, 61.5; H, 5.0. Calc. for C2,H2,010: C, 61.3; H, 4.7%). Polymerisations The following procedures are typical. The results of all the polymerisations are summarised in Table 1.Procedure A: synthesis of polymer PP1. Monomer 9 (1.043 g, 2.22 mmol) was dissolved in a vigorously stirred solution of aqueous sodium hydroxide (0.178 g, 4.45 mmol of sodium hydroxide in 20 ml of water) and tetrabutylammonium bromide J. Muter. Chem., 1996, 6(4), 527-532 531 (56 mg, 8 mmol) was added When the mixture was homo- geneous a solution of sebacoyl chloride (0 531 g, freshly dis- tilled) in chloroform (15 ml) was added rapidly and the mixture was stirred vigorously for 2 h at 20°C Stirring was then stopped and the organic layer added to acidic methanol (600 ml of methanol containing a few drops of concentrated hydrochloric acid) This precipitated the polymer It was collected and washed successively with copious amounts of water then a small amount of methanol and then dried to give the product PP1 (1 25 g, 78%), v,,,(evaporated film from chloroform)/cm-' 1745 (ester groups), 6, 140 (8 H, br s, central 4 methylenes of aliphatic chain), 170 (4 H, br m, two methylenes of aliphatic chain), 240 (6 H, s, 9-and 10-OCOCH3), 2 50 (4 H, br m, 2 x -CH2CO-), 4 50 (2 H, s, 2 x bridge C-H), 7 0-9 0 (6 H, m, ArH) (Found C, 63 5, H, 5 9 Calc for (C&t3@1()),, C, 64 2, H, 5 7%) Procedure B synthesis of polymer PP3.Monomer 9 (2 303 g, 4 9 mmol) was neutralised with aqueous tetrabutylammonium hydroxide (6 300 g of a 40% solution, 9 7 mmol) Water (15 ml) was added and the mixture was stirred vigorously until the mixture was homogeneous A solution of isophthaloyl dichlor- ide (0986 g, 49mmol) in chloroform (20ml) was added quickly The mixture was stirred vigorously for 48 h at 20°C under a nitrogen atmosphere The product was isolated using the procedure outlined above to give polymer PP3 (261g, 90"/0), v,,,(evaporated film from chloroform)/cm-' 1745, 6, 2 45 (6 H, s, 9-and 10-OCOCH,), 3 50 (6 H, s, 2 x C02CH,), 4 75 (2 H, s, bridge C-H) and 7 00-9 00 (10 H, m, 10 x ArH) (Found C, 63 0, H, 4 1% Calc for (C32H24012)n C, 64 0, H, 40%) Procedure C: synthesis of polymer PP7.Monomer 9 (2 923 g, 6 20 mmol, assuming 95% pure 5 91 mmol), sodium hydroxide (0 390 g, 9 75 mmol) and aqueous tetrabutylammonium hydroxide (563 mg, 2 23 mmol in 60 ml of water) were stirred together for 5 min 4,4'-Biphenyldicarbonyl dichloride (1 654 g, 5 9 mmol) in chloroform (60 ml) was added rapidly and the two-phase system was vigorously stirred at 20 "C for 24 h The product was isolated using the procedure outlined above to give polymer PP7 (3 92 g, 97%), v,,,(film formed by evapor- ation of a chloroform solution)/cm-' 1757 and 1740, dH 245 (6 H, s, 9- and 10-OCOCH,), 3 50 (6 H, s, 2 x C02CH,), 4 75 (2 H, s, 2 x bridge C-H), 7 0-7 7 (6 H, m, aromatic H of adduct), 7 80 (4 H, d, 4 x biphenyl ArH 'inner') and 8 30 (4 H, d, ArH next to biphenyl C=O (Found C, 66 5, H, 4 3 Calc for (C38H28012)n C, 67 4, H, 4 1%) Conversion of precursor polymers into final polymers The conversions of the precursor polymers into the final polymers were monitored by DSC and by TGA using ca 5 mg samples The results are summarised in Table 2 To monitor the conversions by UV spectroscopy, films of the precursor polymers ca 1 mm thick were cast from solutions in chloroform onto quartz microscope slides UV spectra were measured, then the films were heated in a vacuum oven (< 1 mm Hg) at 200 "C for 2 days UV spectra were again measured In most cases thicker films, ca 2 mm thick, of the precursor polymer were cast in Petri dishes from chloroform solutions and heated in a vacuum oven as before The films of the final polymers were broken up and the pieces used to measure FT- IR spectra, Get, and for elemental analyses The results from the latter two measurements are summarised in Table 2 We thank the SERC (now EPSRC) and ICI (Wilton) for a CASE Students hip References 1 Comprehensive Polymer Science, ed G Allen and J C Bevington, Pergamon, Oxford, 1989, vol 7, pp 473-592 2 M G Dobb and J E McIntyre, Adv Polym Sci , 1984,60/61,61 3 Important recent examples are discussed in the following refer- ences R A Dine-Hart and W W Wright, J Appl Polym Scz, 1967, 11, 609, V Chaturvedi, S Tanaka and K Kaeriyama, Macromolecules, 1993, 26, 2607, D R Gagnon, J D Capistran, F E Karasz, R W Lenz and S Antoun, Polymer, 1987,28,567 4 See, for example, T Yamamoto 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Hannaford, V Rogers, P W G Smith and A R Tatchell, Longman Scientific and Technical, Harlow, England, 4th edn , 1978, p 291 (method 2) Paper 5/06304C, Received 25th September, 1995 532 J Muter Chem, 1996, 6(4), 527-532