GB2352449A - Synthesis of polycarbonates - Google Patents
Synthesis of polycarbonates Download PDFInfo
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- GB2352449A GB2352449A GB9909756A GB9909756A GB2352449A GB 2352449 A GB2352449 A GB 2352449A GB 9909756 A GB9909756 A GB 9909756A GB 9909756 A GB9909756 A GB 9909756A GB 2352449 A GB2352449 A GB 2352449A
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- C07D317/00—Heterocyclic compounds containing five-membered rings having two oxygen atoms as the only ring hetero atoms
- C07D317/08—Heterocyclic compounds containing five-membered rings having two oxygen atoms as the only ring hetero atoms having the hetero atoms in positions 1 and 3
- C07D317/10—Heterocyclic compounds containing five-membered rings having two oxygen atoms as the only ring hetero atoms having the hetero atoms in positions 1 and 3 not condensed with other rings
- C07D317/32—Heterocyclic compounds containing five-membered rings having two oxygen atoms as the only ring hetero atoms having the hetero atoms in positions 1 and 3 not condensed with other rings with hetero atoms or with carbon atoms having three bonds to hetero atoms with at the most one bond to halogen, e.g. ester or nitrile radicals, directly attached to ring carbon atoms
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- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G64/00—Macromolecular compounds obtained by reactions forming a carbonic ester link in the main chain of the macromolecule
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- B01J2531/0241—Rigid ligands, e.g. extended sp2-carbon frameworks or geminal di- or trisubstitution
- B01J2531/025—Ligands with a porphyrin ring system or analogues thereof, e.g. phthalocyanines, corroles
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- B01J2531/0241—Rigid ligands, e.g. extended sp2-carbon frameworks or geminal di- or trisubstitution
- B01J2531/0252—Salen ligands or analogues, e.g. derived from ethylenediamine and salicylaldehyde
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- B01J2531/90—Catalytic systems characterized by the solvent or solvent system used
- B01J2531/92—Supercritical solvents
- B01J2531/922—Carbon dioxide (scCO2)
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Abstract
The use of CO<SB>2</SB>-insoluble organometallic catalysts for the copolymerisation of various 1,2-cyclohexene oxide derivatives with carbon dioxide (CO<SB>2</SB>) using supercritical carbon dioxide as both solvent and reactant to give an aliphatic polycarbonate, and also for use as catalysts for small molecule transformations in CO<SB>2</SB> is described. As an example, a CO<SB>2</SB>-insoluble catalyst, tetraphenyl porphyrin chromium (III) chloride (CrTPPCl), was synthesised and used to catalyse the copolymerisation of cyclohexene oxide and CO<SB>2</SB> in the presence of 4-dimethylamino pyridine (DMAP) as a co-catalyst, with high catalyst efficiencies (8 kg polymer/ g Cr). The synthesis of the catalyst and its use for copolymerisations are both simple procedures, and the resultant polymers contain high percentages of carbonate linkages, and have narrow molecular weight distributions. Strained ring heterocycles such as epoxides other than cyclohexene oxide or its derivatives, yield cyclic carbonates with similar efficiencies under like conditions.
Description
2352449 Synthesis of Polycarbonates The present invention relates to the
provision of catalysts which are effective for catalysing reactions of epoxides and other strained heterocyclic ring compounds in supercritical carbon dioxide (SCC02) to produce organic carbonates and analagous products incorporating the relevant heteroatom, respectively. In particular certain C02-insoluble organometallic catalysts have been identified and shown to provide a simple route to polycarbonates having very narrow molecular weight distributions and high incorporation of C02' Aliphatic polycarbonates in particular are a useful class of materials. For example, poly(propylene carbonate) has pseudoplastic fluid properties (S.J. Wang, Y.H. Huang, B. Liao, G. Lin, G.M. Cong and L.B. Chen, Internat. J. Polym. Anal. Characterisation, 1997, 3, 131-143). It has also been used to toughen and improve the brittleness of cured epoxy resins (Y.H. Huang, J. Z. Wang, B. Liao, M. C. Chen, and G. M. Cong, J. Appl. Polym. Sci., 1997, 64, 2457-2465). Polycarbonate-sulfones exhibit high barrier properties to permeability by carbon dioxide (T. H. Zhang, M. H. Litt and C. E. Rogers. J. Polym. Sci. B, Polym. Phys., 1994, 32, 16711676). Copolycarbonates with high aliphatic content have possible applications as optical plastics (C. C. Geiger, J. D. Davies and W. H. Daly, J. Polym. Sci. A, Polym. Chem., 1995, 33, 2317-23 27).
Supercritical carbon dioxide (scC02) is an attractive solvent choice since it is inexpensive, non-toxic, and non-flammable. Under ordinary physical conditions, C02 exists as a gas and does not exhibit the properties of a liquid solvent, however at sufficiently high pressures and temperatures, C02 can exist as a supercritical fluid (SCF). Carbon dioxide has a relatively accessible critical temperature (TC = 31.1 'C) and critical pressure (Pc = 73.8 bar) in comparison with most substances (M. A. McHugh; V. J. Krukonis, Supercritical Fluid Extraction; 2nd Edn., Butterworth-Heinemann, 1994). Supercritical carbon dioxide has been found to be a suitable substitute for volatile organic solvents in polymerisation processes (D.A. Canelas et al., Adv. Polym. Sci., 1997, 103).
2 Previously, Darensbourg et al. have shown that scC02 can be used as both solvent and reactant (D.J. Darensbourg et al., Macromolecules, 1995, 28, 7577.) for the copolymerisation of cyclohexene oxide with C02 to form polycarbonates using a heterogeneous, C02-insoluble zinc glutarate catalyst. Catalyst efficiency was somewhat low (i.e., -370g polymer/g Zn), possibly because of the heterogeneous nature of the catalyst.
Subsequently, Super et al. demonstrated the formation of polycarbonates in SCC02 using a C02-soluble polymerisation catalyst (M. Super et al., Macromolecules, 1997, 30, 368). The copolymerisation Of C02 and cyclohexene oxide was carried out using a C02-soluble partially fluorinated zinc alkyl catalyst to give somewhat improved catalyst efficiencies (400 g polymer / g Zn). In this case, the reaction mixture was initially homogeneous, however the polycarbonate precipitated from the supercritical solution as it was formed. As in Darensbourg's system, the molecular weight distributions were very broad (Mw/Mn = 2.4-27), indicating very little molecular weight control. Furthermore, the formation of cyclohexene carbonate was observed and the reaction had to be carried out under strictly inert conditions. Careful purification of the monomer also seemed to be essential.
Inoue and coworkers (T. Aida et al., Macromolecules, 1986, 19, 8.) investigated the aluminium. metalloporphyrin-catalysed alternating copolymerisation of epoxides with C02. Typically, polymerisations were carried out in CH2Cl2 at ambient temperature for long periods (12-23 days) to form altemating copolymers with 100% polycarbonate linkages and very narrow molecular weight distributions (Mn = 6,200 g/mol, Mw/Mn= 1. 06). Chromium (111) tetra-ptolylporphyrin was reported to be an efficient catalyst for the formation of cyclic carbonates from epoxides (W.J. Kruper et al., J. Org. Chem,. 1995, 60, 725). Reactions were carried out in neat epoxides with or without presence of a co-solvent such as methylene chloride.
Despite the apparent advantages, the application of porphyrin complexes in organic synthesis and polymer chemistry has been limited so far to use in certain traditional solvents; most metallated porphyrins exhibit negligible solubility inSCC02. However, by addingC02philic moieties such as fluorinated groups, it was assumed that it would be possible to generate 3 C02-soluble metalloporphyrin complexes. For example, tetrakis(pentafluorophenyl)porphyrinato iron (III) chloride is active as a selective aerobic oxidation catalyst in the supercritical medium (X.-W. Wu et al. Chem. Lett., 1997, 1045), while the present applicant has demonstrated that tetra(pentafluorophenyl)porphyrin chromium (III) chloride will catalyze the co-polymerisation of 1,2-cyclohexene oxide withC02 usingSCC02as both solvent and reactant.
It will be appreciated that, upto the present time, the emphasis has been directed to obtaining catalysts which demonstrate good solubility in the supercriticaIC02medium and the use of insoluble materials for catalysing copolymerisations of epoxides withC02 togenerate aliphatic polycarbonates has not been thought to be feasible.
However the applicant has now surprisingly found that is possible to use C02-insoluble metallated porphyrin catalysts for the formation of polymers in scC02, or for the catalytic reaction of organic substrates with C02 itself to form useful small molecule products. The present invention is therefore based on the observation that whilst porphyrin complexes bearing an alkyl substituent in the meso-position are insoluble in both liquid and supercritical C02, Yet they unexpectedly act as efficient catalysts in ring opening epoxide copolymerisations and in formation of cyclic carbonates. Similar activity has also been observed for certain salen complexes. (Salen based metal complexes are well known for the asymmetric ring-opening reaction of epoxides (K. B. Hansen et al. J. Am. Chem. Soc., 1996, 118, 10924). In addition, Schiff base complexes have been reported also for the oligornerisation of epoxides to form polyether (A. Le Borgne et. al. Makromol. Chem., Macromol. Symp., 1993, 73, 37). However, their use as an initiator for the copolymerisation of an epoxide with C02 was not known prior to the discoveries made by the present applicant).
Accordingly the present invention provides a process for the controlled reaction of carbon dioxide with a strained ring heterocyclic monomer which comprises reacting the monomeric species in supercritical carbon dioxide in the presence of an organometallic catalyst and a base selected from non-nucleophilic and non-protic, nucleophilic bases, the organometallic catalyst and the monomeric species being together selected such that the catalyst is at least partially soluble in 4 the monomer/Co2binary mixture, and separating off the cyclic carbonate product formed, wherein the organometallic catalyst is selected from the group comprising tetraphenyl porphyrin metal halides having the formula (1), metallo-porphyrazines of formula (II), metallophthalocyanines having the formula (111), metallo-glyoximes of formula (IV) and metal salen complexes having the formula (V):
R, R2 R9 X R10 R8 N R3 N M--- N R 8 9 N N R e7' N R4 R12 R11 R6 R5 R, R2 X N - N R8 N R3 N R7 R4 R6 R5 UP R, R2 R8 N 'N N R3 I N OMO N t 7 N R4 N 6 R5 (111) - R, R2 -N >,X--< N-0, H, I, 0 N m 'Il N / H R4 R3 (m 6 X N N M R 0 0 -R, 4 C R3 R2 (V) where the metal M is selected from the group comprising Al, Zn, Cr, Mo, W, Mn, Tc, Re, Fe, Ru, Os, Co, Rh and Ir, X is halogen selected from F, Br and Cl (preferably Cl) and R, to R,2is H or lower alkyl (C, to C, preferably C, to C4) except that in (1) R, to R8are H and R9 to R,2are phenyl groups.
The metal in the organometallic species is preferably selected from among Cr, Co, Fe, Zn, Al, Mn, and Ti. The most preferred metal is Cr(III). Those of the organornetallics which are preferred for use as catalysts for the ring opening reactions are the tetraphenyl porphyrin metal halides and the metal salen complexes, of which the former are the most preferred.
Especially preferred organometallics include tetraphenyl porphyrin chromium chloride (formula (1) where X = Cl and M = Cr) and the chromium salen complex of formula (V) where M = Cr.
The advantages associated with porphyrin catalysis for polymer synthesis as observed in traditional solvents have also been observed in their use in SCC021 i.e., low molecular weight distributions and insensitivity to impurities. Using epoxides as the strained ring heterocycle substrate, polycarbonates can be formed in fair to good yields without the use of any volatile organic solvents in the polymerisation process and with high carbonate content (90-97 %). In addition, catalyst efficiencies have been found to be considerably higher than any reported so far for a SCF-based process of this type.
7 The non-fluorinated porphyrin complexes also demonstrate advantage over the abovementioned fluorinated analogues in terms of higher catalytic efficiency and they are also less costly. The greater efficiency is assumed to be associated with the absence of the electronwithdrawing pentafluorophenyl substituents on the porphyrin ligand.
Despite the total lack of solubility of the tetraphenyl chromium porphyrin complex (1, X Cl, M = Cr) in both pure liquid and supercritical C02 at moderate pressures (70-250 bar) and temperatures (20-800C), it was found, surprisingly, that the complex could be dissolved in the binary mixture of, for example, cyclohexene oxide and carbon dioxide over the above temperature and pressure range. Unexpectedly the solubility of the macrocycle was found to be sufficiently high in this case for it to be feasible to employ the complex in the copolymerisation reaction.
The chromium salen complex (formula (V), M = Cr), viz.Cr(III) (R,R)-(-)-N, N'-Bis(3,5di-tert-butylsalicylidene)-1,2-cyclohexanediamine complex, was likewise found to be insoluble in both pure liquid and supercritical C02 over a range of pressures (70-250 bar) and temperatures (20-95'C) but could surprisingly be dissolved in the binary mixture of cyclohexene oxide and carbon dioxide. Again, the solubility of the macrocycle was sufficiently high in this case for it to be possible to employ the complex as an effective catalyst in the epoxide/C02 copolymerisation reaction to form polycarbonates.
Based on these observations a range of organometallic catalysts which are alone insoluble in scC02 are expected to be soluble in the binary reaction mixtureof C02with a range of strained ring heterocyclic monomers and hence to find application in useful ring opening reactions with potentially high levels Of C02 incorporation.
It has been found necessary to utilise a base in conjunction with the metalloporphyrin or salen complex catalysts in order to obtain the desired polymeric products. Bases which may be used include non-protic, nucleophilic, bases such as triphenyl phosphine and non-nucleophilic 8 bases such as hindered pyridine and amidine bases, specific examples including imidazole, Nmethyl imidazole and dimethylamino pyridine (DNIAP) which is the most preferred base.
Access to a wide range of products incorporating C02 by ring opening polymerisation in SCC02 will be available by this process of the present invention using the aforementioned catalyst system. Suitable monomers for this process include episulphides and aziridines (to yield, respectively, polysulfocarbonates and polyurethanes) as well as the preferred epoxide and oxetane monomers.
In the case of epoxides, the process of the invention provides either polycarbonates (where the monomer is cyclohexene oxide or a cyclohexene oxide derivative) or a cyclic carbonate where another type of epoxide is used, for example, cyclopentene oxide or propene oxide.
Accordingly in a further aspect, the present invention provides a process for the controlled alternating copolymerisation Of C02 with cyclohexene oxide or a derivative thereof which comprises reacting the monomeric species in supercritical carbon dioxide in the presence of an organometallic catalyst selected from the group comprising tetraphenyl porphyrin metal halides having the formula (I), metallo-porphyrazines of formula (II), metallo-phthalocyanines having the formula (111), metalloglyoximes of formula (IV) and metal salen complexes having the formula (V) where the metal is selected from the group comprising Zn, Al, Sri, Ti, Cr, Mo, W, Mn, Tc, Re, Fe, Ru, Os, Co, Rh and Ir, and a base, the organometallic catalyst and the monomeric species being together selected such that the catalyst is at least partially soluble in the monomer/C02 binary mixture, and separating off the copolymer formed.
In an another preferred aspect the present invention provides a process for the preparation of cyclic carbonates which comprises reacting a strained ring oxygen-containing heterocyclic monomer (other than cyclohexene oxide or a derivative thereof) in supercritical carbon dioxide in the presence of an organometallic, catalyst of the present invention and a base, the organometallic catalyst and the monomeric species being together selected such that the catalyst is at least 9 partially soluble in the monomer/C02 binary mixture, and separating off the cyclic carbonate formed.
Preferred monomers for the latter process are cyclic and acyclic epoxides, such as cyclopentene oxide, propylene oxide and glycidyl phenylether.
In the case of either of the above processes of polycarbonate or cyclic carbonate formation respectively, the organometallic catalyst used is preferably a tetraphenyl porphyrin metal halide or a metal salen complex, of which the former is most preferred. The base is either a nonnucleophilic base or a non-protic nucleophilic base, preferably the former and the most preferred base is DMAP.
The invention will now be further described with reference to the following examples. In the polymerisation reactions (Examples 2, 3, 6 to 11), a 10 cm' Hastalloy steel reactor, equipped with a sapphire view window, was used in all cases. Liquid carbon dioxide was delivered to the reactor using a Pickel PM 10 1 nitrogen driven pump. The pressure in the reactor was measured with a pressure transducer (A 105, RDP Electronics) and displayed on a digital display (E3 08, RDP Electronics). The internal temperature was measured with an Industrial Mineral Isolated thermocouple (TypeK, RS Electronics) and displayed on a temperature indicator (T 200, RS Electronics). A PTFE-coated magnetic stir bar was used to mix the contents of the reactor.
Example I - Preparation of Tetraphenyl Porphyrin Chromium (III) chloride (CrTPPCI) Tetraphenyl porphyrin (TPPH2) (100 mg) was dissolved in anhydrous DMF (20 cm3) and an excess of anhydrous chromium(II) chloride was added under an inert atmosphere. The mixture was stirred under reflux for I hour, allowed to cool, and the solvent evaporated. The crude product was purified by flash column chromatography with acetone as the eluent over neutral alumina to give the corresponding chromium porphyrin complex (80 mg, 75.5 %).
kmax(CHC13)/nm 278, 332, 404, 442, 618; v.,,.,KBr/crn-': 2988, 2973, 1422, 13 85, 1265, 746, 73 9, 706; FAB-MS 730 (M-H+) (calcd mass).
Example 2 - Synthesis of poly(cyclohexene carbonate) (PCHQ In a typical reaction, tetraphenyl porphyrin chromium (III) chloride (CrTPPCI) (prepared as above)(5 mg, 7xlO-3 mmol), 4-dimethylarnino pyridine (DMAP) (5 mg, 0.04 mmol) and cyclohexene oxide (2.5 g, 25 mmol) were added to the reactor. The reaction vessel was then filled with liquid carbon dioxide to approximately 3/4 full and the solution was heated to the reaction temperature and stirred for the desired period. In all cases, the copolymer was observed to precipitate from solution as it was formed (Scheme I):- 0 0 0 0 CrTPPCI/DMAP SCC02 (235 bar) 70-110 OC, 18h M n Scheme 1 - Preparation of PCHC After the allotted reaction time, the carbon dioxide was vented into an excess of acetone to trap residual monomer and any remaining products in the reactor were rinsed into the same solution. The solvent was then partially evaporated and the concentrated polymer solution was precipitated into an excess of hexane to give the polycarbonate as a powder in comparatively high yield (1. 1 g, 56 %). (Found (one example): C, 59. 1; H, 7.2. C71-11 003 requires C, 59. 1; H, 7.2%); v..film /cm- 1 2987, 2939,2861 (vCH), 1748 (vC=O), 1459,1439 OCH), 1357, 1260 (vC-O), 1188, 1088, 967, 891, 837; 8H (250 MHz, CDC13) 4.63 (2H, br s, 1 CHOC(0)0-), 3.57 (21-1, br s, -4CH-O-), 2.23-2.09,1.90-1.70 (41-1, br s, -2CH2-), 1.44-1. 24 (4H, br m, -3 CH2-); 8c (62.5 MHz, CHC13) 153.8 (-C(O)-syndio), 153.1 (-C(O)-iso), 82.2, 72.5, 53.8, 32.6, 31.7, 30.9, 11 29.3, 23.8, 22.8 2 C112), (-3CH2-); GPC assay in CHC13 revealed Mw 22,650, Mn 15,100 and Mw/Mn 1. 5; maximal decomposition: Tmax = 3 10 C; glass transition temperature T9= 117 OC.
In a number of reactions carried out using the general protocol described above, PCHC was synthesised at different reaction temperatures while keeping all other variables constant. In all cases the polymerisation was left for 18 h, but precipitation of product commenced after a few hours. The reaction appeared to be temperature dependent, but not overly sensitive to air and water. For example, the reaction was carried out under identical conditions except that in one case conditions were rigorously anaerobic and dry whilst in the other case no special precautions were used. The two reactions did not differ significantly in terms of yield, percentage of carbonate linkages, or polymer molecular weight. At lower temperatures, only oligomeric polyether formation was observed. The use of higher temperatures (70-11 O'C) was found in general to lead to higher C02 incorporations (in =95% at temperatures of 70'C and above) and higher polymer yields. At temperatures in the range of 95-11 O'C, molecular weights (M.) were around 4500 g mol', whereas at 140'C a significant increase in molecular weight to M. = 9160 g mol' was observed.
The effect on the copolymerisation reaction of varying the volume fraction of cyclohexene oxide (CHO) was also explored. In all cases, the polymerisations were left for 18 h at 95 'C/3300 psi and conducted in the one-phase region, (i.e., where catalysts and monomer were completely soluble in C02). The catalyst to monomer ratio (NCrTppCI/NCHO) was kept constant. At low volume fractions (below (CHO) = 25% w/v), the yield of polymer is somewhat poor but at higher volume fractions, yields are much higher (around 90%). The variation of monomer volume fraction seemed to have no effect on the percentage Of C02 incorporation, molecular weight or polydispersity, molecular weight distribution, the latter of which was low throughout (of the order of 1.2).
Since the results on volume fraction of the monomer indicated that the monomer concentration was important for high conversion rates, all following experiments were carried out with an initial volume fraction of at least (CHO) = 25 % w/v.
12 In a separate series of reactions, the C02 pressure was varied while the temperature (95'C) and time (18 h) were kept constant. Initial studies were carried out in the two-phase region at 1000 psi and 2000 psi. Under these conditions, a monomer rich phase and or C02-rich phase were clearly discernible in the reaction vessel. The catalyst appeared to reside only in the monomer rich phase. At the lowest pressure a surprisingly high molecular weight material (Mn = 13400 g mol- 1) could be isolated. By increasing the pressure to 2000 psi, the number average molecular weight decreased significantly. Further increases in pressure to 3300 psi and 4500 psi did not have an effect on the molecular weight. The reason for the significant increase in Mn at lower pressures is as yet unclear.
Yields were in the range of 84 - 92% except at the highest pressure (4500 psi) where a decrease was observed. This could be due to the variation in phase behaviour between experiments. Cyclohexene oxide/carbon dioxide mixtures at 95'C/1 000 psi and 2000 psi appeared to be biphasic, consisting of a monomer-rich phase (lower layer) and a C02-rich layer (upper layer). By contrast, the polymerisations conducted at 95'C/3300psi and 4500 psi were initially in a one-phase homogeneous region. In the first case, the polymerisation was performed under conditions similar to polymerisation in bulk. The concentration of CHO in the monomerrich C02phase would be high, which keeps the polycarbonate in solution for a longer time before eventual precipitation. By increasing the pressure from 1000 to 2000 psi the concentration of CHO in the lower layer is likely to be decreased, thereby reducing the solvent strength of this layer because of dilution by C02. This situation could also potentially explain the decrease in molecular weight at higher pressures. In the experiments conducted in the onephase region, the effective concentration of CHO is even lower compared to the experiments in the two-phase region, consequently one might expect the material to precipitate from solution at an earlier stage. In addition, even though the same volume of CHO and the same weight of catalyst were used for this series of experiments, the actual fraction of CHO decreased with increasing pressure due to the change in density of carbon dioxide. For example, the density of pure C02 changes from 0. 127 g mol-1 at 1000 psi/95'C to 0.694 g mol-I at 4500 psi/95'C.
13 In a further series of reactions the effect of initiator to monomer ratio NCrTppCI/NCHO was investigated. In terms of yield and molecular weight the optimum ratio seemed to be around NCrTppCI/NCHO = 2.8 x 104. This ratio did not, however, seem to have a significant effect on the C02-incorporation rate or the molecular weight distribution, which remained below M_ '/ M_. < 1.20 in all cases.
In order to investigate the effect of time on the copolymerisation of CHO/CO2, the polymerisations were conducted for different periods from 172 hours. Precipitation of polymer was observed to commence even after one hour at the reaction temperature. The highest yield was observed after 18 h. The number average molecular weight increased with increasing reaction time.
In summary therefore, polymer yield tends to increase with increasing volume fraction of CHO. The non-fluorinated system is not highly sensitive to pressure and phase behaviour regarding the yields. Indeed the effects of pressure seem to be minimal or non-existent at higher initial volume fraction of cyclohexene oxide. They cannot, however, be ignored at lower mole fractions, i.e. (CHO) = 13 % w/v. The copolymerisation of CHO and C02 indicated a significant dependency on temperature in terms of molecular weight and yield.
All of the copolymer products showed a dominant infrared absorption band attributable to linear carbonate linkages at 1750 cm-1. 'H-NMR spectroscopy confirmed that the polymers consisted of polycarbonate homopolymer with a very small percentage of polyether linkages. The signal assignable to the methine proton of the repeating oxycarbonyloxy (1,2 cyclohexene) units appears at d = 4.6 ppm, while the signal corresponding to the repeating oxy(1,2 cyclohexene) units at d = 3.5 ppm is barely discernible. By integrating and comparing the area under the two signals, the percentage of carbonate linkages can be determined. Within the limits of accuracy, a very high percentage (95%) of carbonate linkages was calculated.
14 Gel permeation chromatography was used to characterise the polymers, which are soluble in CHC13. The number average molecular weights of the copolymers were in the range Mn = 3 500-15 000 g/mol. However, considering that the copolymerisation is a precipitation process, the GPCchromatograms for all the polymers showed narrow unimodal distributions and sharp elution curves. The molecular weight distribution was calculated to be in the range Mw/Mn= 1.21.5 in all cases. This represents a significant improvement over the distributions (Mw/M11 = 2.42.7) reported previously for scC02-based systems.
Example 3: Synthesis of poly(vinylcyclohexene carbonate) (PVCHC) The CrTPPCl/DMAP system (Example 2) showed also catalytic activity for the ring opening copolymerisation of 4-vinyl cyclohexene oxide and C02 to form the copolymer, poly(vinylcyclohexene carbonate-co-cyclohexene ether) (PVCHC), with a high carbonate content (Scheme 2). The reactions generated C02-insoluble polymers, and precipitation commenced during polymerisation. No by-products (e.g.cyclic carbonate) were observed to be formed.
0 11 'C 0 0 0 0 SCC02 235 bar) 70-110 C, 18h M n Scheme 2 - Preparation of PVCHC In a typical reaction, tetraphenyl porphyrin chromium (111) chloride (CrTPPCI) (5 nig, 7.0 x 10-3 mmol), 4-dimethylamino pyridine (DMAP) (5 mg, 0.04 mmol) and 4- vinyl 1,2cyclohexene oxide (2.5 g, 25 mmol) were added to the reactor. The reaction vessel was then filled with liquid carbon dioxide to approximately 3/4 full and the solution was heated to the reaction temperature and stiffed for the desired period. In all cases, the copolymer was observed to precipitate from solution as it was formed. After the allotted reaction time, the carbon dioxide was vented into an excess of acetone to trap residual monomer and any remaining products in the reactor were rinsed into the same solution. The solvent was then partially evaporated and the concentrated polymer solution was precipitated into an excess of hexane to give the polycarbonate as a powder in comparatively high yield (Found: C, 64.0; H, 7.4. CgH1203 requires C, 64.3; H, 7.1 %); vma,,film /cm-' 3082, 2940, 2865, 1748, 1454, 1439, 1329, 1277, 966; IH-NMR 8(250 MHz, CDC13) 5.76 (IH, m, -CH=CH2),5.1-4.7 (4H, m, CHOC(0)0; CH=CH2), 2.4-2.2, 1.9-1.3 (7H, br m, -CH2-;CH-); Tmax = 325'C, Tg = 96T.
This preparation clearly shows that the conditions of the copolymerisation tolerated the presence of a vinyl group. This substitution allows a further polymer analogous reaction to be carried out, i.e. addition to the double bond.
Polymerisations of 4-vinyl cyclohexene oxide were conducted in the one phase (3300 psi) as well as in a biphasic system (2000 psi) and the results were similar in terms Of C02 incorporation and polydispersity. However, the yield and the number average molecular weight were in the biphase case significantly higher, possibly for the reasons discussed in connection with Example 2 above.
Example 4 - Preparation of Cyclic carbonate Propylene oxide (2.5 g, 43 mmol), 4,4-dimethylaininopyridine (5 mg, 0.04 mmol), and tetraphenyl porphyrin chromium(III) chloride (5 mg, 7. 1 x 10- 3 mmol) were given in a Hastealloy cell. The cell was filled 2/3 with C02 and heated to 95 'C with an end pressure of 3000 psi. The reaction was stirred for 16 hrs and after cooling down, C02 was vented into dichloromethane and the crude product could be separated as a liquid. The product was destilled to give 2.2 g (50 %) propylene carbonate bp 65 'C/ 0. 1 mmHg. (Found: C, 46.9; H, 6. 1. C4H603 requires C, 47. 1; H, 5.9 O/o); vmax 2988, 2938, 1790, 1484, 1451, 1389, 1354, 1227, 1182, 105 1; 8H (250 MHz, CDC13) 4.80 (1 H, m, -CH), 4.50 (1 H, t, J= 8 Hz, -CH2), (I H, t, J = 8 Hz, -CH2),1.43 (3 H, d, J = 7 Hz, -CH3), 6c (62.5 MHz, CDC13) 155 (C=O), 73, 70 (-CH, -CH2),19 (-CH3).
16 Example 5 - Synthesis of Cr(III) (R,R)-(-)-N,N'-Bis(3,5-di-tertbutylsalicylidene)-1,2cyclohexanediamine (salen) complex Under a nitrogen atmosphere, 0. 1 g (. 84 mmol) of CrC12 (anhydrous, 99.9 %) was added to (R,Rl)-(-)-N,N'-Bis(3,5-di-tert-butylsalicylidene)-1,2- cyclohexanediamine (0.4 g, 0.76 mmol) in dry THF (20 mL). The resulting brown solution was stirred under N2 for 3 h and then in air for an additional 3 h. The solution was then diluted with 80 mL of t-butyl methyl ether and washed with saturated NH4CI (3xlOO mL) and brine (3xlOO mL). The organic phase was dried (Na2S04) and solvent was removed under reduced pressure, affording 0.47 g (87 % yield) of the complex as a brown solid. This material was used without further purification. (Found: C, 65. 5; H 8.6;N 4.0. C38H59N204CrCI requires C, 65.6; H 8.6; N 4.0 %); v.ax film /cm- 1 2956,2867, 1622,1532,1435, 1391, 1321, 1256, 1169, 1028, 837, 785, FAB-MS 631 (M-H+) (calcd. 632).
Example 6 - Copolymerisation of 1,2-Cyclohexene Oxide and C02 using Cr(III) (R,R)-(-)-NN'Bis(3,5-di-tert-butylsalicylidene)-1,2 cyclohexane diamine (salen) comple In a typical reaction, Cr(III) (R,R)-(-)-N,N'-Bis(3,5-di-tert- butylsalicylidene)-1,2- cyclohexanediamine complex (CrSalenCI) (4 mg, 6.3 x 10-3 mmol), 4- dimethylamino pyridine (DMAP) (5 mg, 0.04 nimol) and cyclohexene oxide (2. 0 g, 20 mmol) were added to the reactor. The reaction vessel was then filled with liquid carbon dioxide to approximately three-quarter capacity, and the solution was heated to the reaction temperature and stirred for the desired period. In all cases, the copolymer was observed to precipitate from solution as it was formed. After the allotted reaction time, the carbon dioxide was vented into excess acetone to trap any residual monomer. Remaining products in the reactor were rinsed with acetone into the same solution. The solvent was then partially evaporated and the concentrated polymer solution was precipitated into an excess of hexane to give the polycarbonate as a fine powder. The polymer was dried under vacuum to constant weight and the yield determined gravimetrically. Analysis as in example 2.
Example 7 - Terpolymerisation of 1,2-Cyclohexene oxide and bis-expoxide (3,4epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate) oxide and carbon dioxide usin tetraphenyl porphyrin chromium (III) chloride (CrTPPCI) In a typical reaction, tetraphenyl porphyrin chromium (III) chloride (CrTPPCI) (5 mg, 7.1 x 10-'mmol), 4-dimethylamino pyridine (DMAP) (5 mg, 0.04 mmol), 1,2-cyclohexene oxide and bis-epoxide(3,4epoxycyclohexylmethyl-3,4-epoxy cyclohexane carboxylate) were added to the reactor. The reaction vessel was then filled with liquid carbon dioxide to approximately threequarter capacity, and the solution was heated to the reaction temperature and stirred for the desired period. In all cases, the copolymer was observed to precipitate from solution as it was formed. After the allotted reaction time, the carbon dioxide was vented into excess acetone to trap any residual monomer. Remaining products in the reactor were rinsed with acetone and the product was filtered to give an insoluble crosslinked polymer.
Example 8 - Terpolymerisation of 1,2-Cyclohexene oxide and 4 -vinyl 1,2cyclohexene oxide and carbon dioxide using tetraphenyl porphyrin chromium (III) chloride (CrTPPCI) In a typical reaction, tetraphenyl porphyrin chromium (III) chloride (CrTPPCI) (5 mg, 7.1 X 10- 3MMOI) 4-dimethylamino pyridine (DMAP) (5 mg, 0.04 mmol), 1,2-cyclohexene oxide (1.3g, 13 mmol) and 4-vinyl-1,2 cyclohexene oxide (1.6g, 13 mmol) were added to the reactor. The reaction vessel was then filled with liquid carbon dioxide to approximately three- quarter capacity, and the solution was heated to the reaction temperature and stirred for the desired period. In all cases, the copolymer was observed to precipitate from solution as it was formed. After the allotted reaction time, the carbon dioxide was vented into excess acetone to trap any residual monomer. Remaining products in the reactor were rinsed with acetone into the same solution. The solvent was then partially evaporated and the concentrated polymer solution was precipitated into an excess of hexane to give the polycarbonate as a fine powder.
18 Example 9 - Preparation of 4-Ethyl-1,3-dioxolan-2-one using tetraphenyl chromium (111) 0 SCC02,95'C, - 0 0 C21-15 3 000 psi, I 6hr L---C2H5 Epoxy butane (2.81 g, 38.8 mmol), 4,4-dimethylaminopyridine (5 mg, 0.04 mmol), and tetraphenyl porphyrin chromium(III) chloride (5 mg, 7. 1 x 10- 3 nimol) were placed in a Hastealloy cell. The cell was filled 3/4 with C02 and heated to 95 T with an end pressure of 3000 psi. If necessary, more C02 was added close to the reaction temperature in order to reach the desired pressure. The reaction mixture was stirred for 18 hrs and after cooling down, C02 was vented into dichloromethane and the crude product could be separated as a liquid. The product was subject to column chromatography to give 570 mg (13 %) butylene carbonate, bp. 59'C/ 0.3 mmHg, (Found: C, 51.8; H,6.9. C51-1.03 requires C, 51.7; H, 5.9%); vmax 2977,2942,2886,1970, 1798, 1553, 1485, 1466, 1439,1377, 1175, 1128, 1111, 1061, 776; 8H (250 MHz, CDC13) 4.60 (1 H, q, -CH), 4.5 0 (1 H, t, J= 8Hz, -CH2), 4. 10 (1 H, t, J= 8 Hz, -CH2), 1.43 (2 H, m, -CH2), 1.43 (3 H, d, J = 71-1z, -CH3); 8c (100 MHz, CDC13) 15 5 (C=O), 78 (-CH), 69 (-CH2), 27 (-CH2), 8.5 CH3)- Example 10 - Preparation of 4-Phenyl- 1,3 -dioxolan-2-one using tetraphenyl porphyrin chromium 0 0 CrTPPCI/DMAP.
SCC02, 95'C, - 0 0 C6145 3000 psi, 18hrL----C 6 H5 (2,3-Epoxypropyl)benzene (2.13 g, 15.8 mmol), 4-dimethylaminopyridine (5 mg, 0.04 mmol), and tetraphenyl porphyrin chromium(III) chloride (5 mg, 7. 1 x 10' mmol) were placed in 19 a Hastealloy cell. The cell was filled 3/4 withC02and heated to 95 OC with an end pressure of 3000 psi. If necessary, moreCo2was added close to the reaction temperature in order to reach the desired pressure. The reaction was stirred for 18 hrs and after cooling down,C02was vented into dichloromethane and the crude product was subject to column chromatography. The product was isolated as a white solid 550 mg (20%) mp 41-43 OC. (Found: C, 67.6; H, 5.7. CIOH1003 requires C, 67.4; H, 5.7 %); vm.KBr/ cm-' 3064, 3031, 2959, 2923, 1802, 1605, 1499, 148 1, 1457, 1395, 1289, 1171, 1080, 1060, 773;8H(250 MHz, CDC13)7.35 -7.20 (5 H, m, Ar-H), 4.90 (1 H, q, -CHO), 4.40 (1 H, m, -CH20), 4.14 (1 H, m, -CH20), 3.10 (2 H, m, -CH2); 5,(100 MHz, CDC13) 162.1(-C=O), 137.3, 133.9,129.3, 129.0 (Ar-Q, 76.6 (-CHO), 66.2 (-CH20),39.6(CH2)' Example 11 - Preparation of 4-Phenoxymethyl-1,3-dioxolan-2-one using CrSalenCl 0 0 CrSaIenCl/DMAP L, SCC02, 95'C' 0.'k 1'OC6H5 3000 psi, 16hr L___OC6H5 Glycidyl phenyl ether (2.33 g, 15.5 mmol), 4-dimethylaminopyridine (5 mg, 0.04 mmol), and Cr(III) (R,R)-(-)-N,N-Bis(3,5-di-tert-butylsalicylidene)- 1,2-cyclohexane diamine (salen) complex (CrSalenCI) (5 mg, 7.8 x 10-' mmol) were placed in a Hastealloy cell. The cell was filled 3/4 withC02and heated to 80 OC with an end pressure of 3500 psi. If necessary, more CO, was added close to the reaction temperature in order to reach the desired pressure. Under this condition, the reaction mixture stayed heterogeneous and a phase separation was observed. The reaction mixture was stirred for 16 hrs and after cooling down, C02was vented into dichloromethane and the crude product could be separated as a crystalline powder. The product was recrystallised from hexane to give 2.90 g (96%) of a white solid. mp 91-92 OC (Lit. 90-92 0Q. (Found: C, 61.7; H, 5.3. C10113004requires C, 61.8; H, 5.1 Yo); v.a,,KBr /cm-' 3089, 2987, 1808, 1800, 1790, 1603, 1588, 1495,1457, 1397, 1253, 1181, 1167, 1092, 1082, 1059, 760; 5H (250 MHz, CDC13) 7.28 (2 H, m, Ar-H), 7.01 (3 H, m, Ar-B), 5.00 (1 H, m, -CHO), 4.56 (2 H, m, -CH20),4.12 (2 H, m, -CH20); 8c(62.5 MHz, CDC13) 157.7 (ipso-ArC), 154. 6 (C=O), 129.7 (m-ArC), 122.0 (p-ArC), 114.6 (o-ArC), 74.1 (CHO), 66.9 (CH20), 66.2 (CH20)- 21
Claims (16)
1. A process for the controlled reaction Of C02 with a strained ring heterocyclic monomer which comprises reacting the monomeric species in supercritical carbon dioxide in the presence of an organometallic catalyst and a base selected from non-nucleophilic and nonprotic, nucleophilic bases, the organometallic catalyst and the monomeric species being together selected such that the catalyst is at least partially soluble in the monomer/C02 binary mixture, and separating off the cyclic carbonate product formed, wherein the organometallic catalyst is selected from the group comprising tetraphenyl porphyrin metal halides having the formula (1), metallo- porphyrazines of formula (H), metallophthalocyanines having the formula (111), metallo-glyoximes of formula (IV) and metal salen complexes having the formula (V):
R, R2 R9 X RIO R8 N R3 N R7 R4 R11 R12 6 R5 22 R, R2 x N -N R8 N I R3 I N 0- 1 N R7 N - 11-11 I N R4 R6 R5 (11) R, R2 R8 N N R3 I I N 0- M----N I f R7 N R4 N N 6 R5 (111) 23 R, R2 0 N >/-< N-0, H, M H N N-0 -N" R>4 R3 (IV) X N N M R4 0 0 -R, C -CF)7 D R3 R2 (V) where the metal M is selected from the group comprising Al, Zn, Cr, Mo, W, Mn, Tc, Re, Fe, Ru, Os, Co, Rh and Ir, X is halogen selected from F, Br and Cl and R, to R,2 is H or lower alkyl (CI to Q except that in (I) R, to R8are H and R9 to R,2 are phenyl groups.
2. A process as claimed in claim I wherein the metal in the organometallic is selected from Cr, Co, Fe, Zn, Al, Mn and Ti.
3. A process as claimed in claim 2 wherein the metal is Cr(III).
4. A process as claimed in any of claims 1 to 3 wherein the organometallic is a tetraphenyl porphyrin metal halide.
24
5. A process as claimed in any of claims 1 to 4 wherein the halogen is chlorine.
6. A process as claimed in any of claims I to 5, wherein the monomer is selected from the group comprising epoxides, oxetanes, episulphides and aziridines.
7. A proOess for the controlled alternating copolymerisation Of C02 with cyclohexene oxide or a derivative thereof which comprises reacting the monomeric species in supercritical carbon dioxide in the presence of an organometallic catalyst and a base selected from non-nucleophilic and nonprotic, nucleophilic bases, the organometallic catalyst and the monomeric species being together selected such that the catalyst is at least partially soluble in the monomer/Co2binary mixture, and separating off the product formed, wherein the organometallic catalyst is selected from the group comprising tetraphenyl porphyrin metal halides having the fornaula (1), metallo-porphyrazines of formula (11), metallo- phthalocyanines having the formula (III), metallo-glyoximes of formula (IV) and metal salen complexes having the formula (V), each formula being as defined in claim 1.
8. A process as claimed in claim 7 wherein the cyclohexene oxide derivative is a substituted cyclohexene oxide such as 4-vinyl cyclohexene oxide or 3,4- epoxycyclohexylmethyl 3,4epoxyclohexane carboxylate.
9. A process for the preparation of cyclic carbonates which comprises reacting a strained ring oxygen-containing heterocyclic monomer (other than cyclohexene oxide or a derivative thereof) in supercritical carbon dioxide in the presence of an organometallic catalyst as defined in claim I and a base selected from non-nucleophilic and non-protic, nucleophilic bases, the organometallic catalyst and the monomeric species being together selected such that the catalyst is at least partially soluble in the monomer/Co2binary mixture, and separating off the cyclic carbonate formed.
10. A process for the preparation of cyclic carbonates as claimed in claim 9 wherein the monomer is a cyclic or acyclic epoxide.
11. A process as claimed in claim 10 wherein the monomer is cyclopentene oxide, propene oxide or glycidyl phenylether.
12. A process as claimed in any one of claims 1 to I I wherein the base is a non-nucleophilic base.
13. A process as claimed in claim 12 where the base is imidazole, Nmethyl imidazole or dimethylamino pyridine (DMAP).
14. A process as claimed in claim 13 where the base is dimethylarnino pyridine (DNIAP).
15. A process as claimed in any one of claims 7 to 14, wherein the catalyst is tetraphenyl porphyrin chromium(III) chloride having the formula (1) where X = CI and M = Cr.
16. A process as claimed in any one of claims 7 to 14, wherein the catalyst is a chromium salen complex of formula (V) where M = Cr.
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| US6870004B1 (en) * | 2001-08-24 | 2005-03-22 | Northwestern University | Metal-ligand complexes and related methods of chemical CO2 fixation |
| CN104327036A (en) * | 2014-10-10 | 2015-02-04 | 中国科学院长春应用化学研究所 | Preparation method of cyclic carbonate |
| JP2016147973A (en) * | 2015-02-12 | 2016-08-18 | 株式会社ダイセル | Polyfunctional epoxy compound and method for producing the same |
| CN109988290A (en) * | 2019-04-22 | 2019-07-09 | 中国科学院长春应用化学研究所 | A kind of preparation method of oligomeric Metalloporphyrins and polycarbonate |
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| CN102229745B (en) * | 2011-06-09 | 2014-04-02 | 大连理工大学 | Crystallizable polycarbonate material based on carbon dioxide and preparation method thereof |
| WO2013042695A1 (en) * | 2011-09-21 | 2013-03-28 | 国立大学法人岡山大学 | Metal porphyrin complex, method for producing same, carbon dioxide immobilization catalyst comprising same, and method for producing cyclic carbonic acid ester. |
| WO2017203044A2 (en) * | 2016-05-27 | 2017-11-30 | Dsm Ip Assets B.V. | Polymers, processes, compositions & uses |
| CN115591586B (en) * | 2022-10-24 | 2024-03-15 | 西华师范大学 | Application of super-crosslinked polymer supported metal catalyst in synthesis of cyclic carbonate |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
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| US6870004B1 (en) * | 2001-08-24 | 2005-03-22 | Northwestern University | Metal-ligand complexes and related methods of chemical CO2 fixation |
| CN104327036A (en) * | 2014-10-10 | 2015-02-04 | 中国科学院长春应用化学研究所 | Preparation method of cyclic carbonate |
| JP2016147973A (en) * | 2015-02-12 | 2016-08-18 | 株式会社ダイセル | Polyfunctional epoxy compound and method for producing the same |
| CN109988290A (en) * | 2019-04-22 | 2019-07-09 | 中国科学院长春应用化学研究所 | A kind of preparation method of oligomeric Metalloporphyrins and polycarbonate |
| CN109988290B (en) * | 2019-04-22 | 2021-05-28 | 中国科学院长春应用化学研究所 | Preparation method of oligomeric metalloporphyrin complex and polycarbonate |
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