Copolymerization of carbon dioxide

Incorporation of carbon dioxide as a reactive comonomer has been studied by several groups. Inoue et al. were the first to succeed in preparing high molecular weight polycarbonates by the copolymerization of carbon dioxide and propylene oxide241,242 ... 

Inoue S, Koinuma H, Tsumta T (1969) Copolymerization of carbon dioxide and epoxide. J Polym Sci Part B Polym Lett 7 287-292... 

Wang JT, Zhu Q, Lu XL, Meng YZ (1995) ZnGA-MMT catalyzed the copolymerization of carbon dioxide with propylene oxide. Eur Polym J 41 1108-1114... 

Tan C-S, Chang C-F, Hsu T-J (2002) Copolymerization of carbon dioxide, propylene oxide and cyclohexene oxide by a yttrium-metal coordination catalyst system. In CO2 conversion and utilization. ACS Symp Ser 809 102-111... 

Hsu T, Tan C (2002) Block copolymerization of carbon dioxide with cyclohexene oxide and 4-vinyl-1-cyclohexene-1,2-epoxide in based poly(propylene carbonate) by yttrium-metal... 

Wang JT, Shu D, Xiao M, Meng YZ (2006) Copolymerization of carbon dioxide and propylene oxide using zinc adipate as catalyst. J Appl Polym Sci 99 200-206... 

Kim G, Ree M, Kim H, Kim IJ, Kim JR, I-ee JI (2008) Biological affinity and biodegradability of poly(propylene carbonate) prepared from copolymerization of carbon dioxide with propylene oxide. Macromol Res 16 473-480... 

In addition to the polymerization of dienes the versatility of NdP-based catalysts is exceptional regarding the number of different non-diene monomers which can be polymerized with these catalysts. Acetylene is polymerized by the binary catalyst system NdP/AlEt3 [253,254]. Lactides are polymerized by the ternary system NdP/AlEt3/H20 [255,256]. NdP/TIBA systems are applied in the copolymerization of carbon dioxide and epichlorhy-drine [257] as well as for the block copolymerization of IP and epichloro-hydrin [258]. The ternary catalyst system NdP/MgBu2/TMEDA allows for the homopolymerization of polar monomers such as acrylonitrile [259] and methylmethacrylate [260]. The quaternary system NdP/MgBu2/AlEt3/HMPTA is used for the polymerization of styrene [261]. 

Figure 9.8 Copolymerization of carbon dioxide in a switchable polarity solvent.

SCHEME 6.11 Heterogeneous catalysis of the copolymerization of carbon dioxide and propylene carbonate on Zn-based catalysts. 

Carbon dioxide is considered to be an interesting alternative to most traditional solvents [17, 18] because of its practical physical and chemical properties it is a solvent for monomers and a non-solvent for polymers, which allows for easy separation. To a somewhat lesser extent, it can also be a sustainable source of carbon [19]. The use of CO2 as a reactant is considered to contribute to the solution of the depletion of fossil fuels and the sequestration of the greenhouse gas CO2. One example in this area is the copolymerization of carbon dioxide with oxiranes to aliphatic polycarbonates [19-22]. 

Copolymerization of carbon dioxide possibly also belongs to this class of polymerizations. Carbon dioxide copolymerizes with epoxides to polyanhydrides, with aziridines to polyurethanes, and with vinyl ethers to poly-ketoethers, i.e.. 

Carbon dioxide is an interesting synthetic feedstock, it can be copolymerized with heterocycles, such as epoxides, aziridines, and episulfides. In 1969, Inoue reported the zinc catalyzed sequential copolymerization of carbon dioxide and epoxides as a new route to polycarbonates (5,15). The reaction is shown in Figure 1.1. 

Copolymerization of carbon dioxide is another example where the monomer may function both as a reactant and a solvent. Historically, the interest in copolymerization of carbon dioxide has been in connection with a desire for carbon dioxide fixation [13, 14]. Recent interest however is in the use of CO2 not only as a reactant, but also as a solvent... 

A more recent example where carbon dioxide has been used as a solvent and reactant is the copolymerization of carbon dioxide with cylohexene oxide to produce poly(cyclohexene carbonate) [16]. In this study, in contrast to earlier studies, a zinc-based but fluorinated catalyst with the following structure... 

It should be noted that in a recent study on copolymerization of carbon dioxide and propylene oxide in 1,3 dioxolane, it was also reported [25] that the yield is enhanced with pressure from 14 to 43 bar, but with further increase in pressure there is a decrease in the yield. This unexpected affect of the increased pressure was attributed to the swelling (expansion) of the solvent as a result of greater dissolution of carbon dioxide in the solvent, which causes a reduction in the solubility of the copolymer. At pressures greater than 43 bar, molecular weight of the polymer was observed to decrease also. 

Inoue, S. Koinuma, H. and Tsurata, T. (1969) Copolymerization of carbon dioxide andepoxide, J. Appl. Polm. Sci. Part B Polymer Letters, 7, 287. 

Darensbourg, D. J., Stafford, N. W. andKatsurao, T. (1995) Supercritical carbon dioxide as solvent for copolymerization of carbon dioxide and propylene oxide using a heterogeneous zinccarboxylate catalyst, J. Molecular Catalysis A Chemical 104, L1-L4. 

Tan, C. S. and Hsu, T. J. (1997), Alternating copolymerization of carbon dioxide and propylene oxide with a rare earth metal coordination catalyst. Macromolecules, 30, 3147-3150. 

COPOLYMERIZATION OF CARBON DIOXIDE AND EPOXIDE AND RELATED REACTIONS... 

We have found for the first time the alternating copolymerization of carbon dioxide and epoxide catalyzed by some organometallic systems to give an aliphatic polycarbonate of high molecular weight. 

The reaction has been studied intensively, and earlier results including the mechanistic aspects of the reaction as well as the fundamental properties of the copolymer were reviewedThe most effective catalyst systems for this copolymerization so far examined are those based on organozinc and related compounds ). The catalyst systems so far reported, from several groups, for the copolymerization of carbon dioxide and epoxide (mainly propylene oxide) are summarized in Table 1. Diethylzinc-water system is applicable to the copolymerization of carbon dioxide and various epoxides (Table 2). 

Table 1. Catalyst Systems for the Copolymerization of Carbon Dioxide and Epoxide...

It is of particular interest to note that this block copolymer has a very narrow molecular weight distribution, as shown in Fig, 9, which also indicates the absence of the prepol3mier in the final procuct. Therefore, the copolymerization of carbon dioxide and propylene oxide actually takes places from the growing end of the epoxide pol3nneri-zation, an aluminum alkoxide. 

Cheng M, Lobkovsky EB, Coates GW (1998) Catalytic reactions involving Cl feedstocks new high-activity Zn(II)-based catalysts for the alternating copolymerization of carbon dioxide and epoxides. J Am Chem Soc 120 11018-11019... 

Inoue, S. Komuma,R Tsuruta,T. Copolymerization of Carbon Dioxide and Epoxide J. Polym. Sci., PartB 1969, 7,287-292. 

Sugimoto, H. Ohshima, H. Inoue, S. Alternating Copolymerization of Carbon Dioxide and Epoxide by Manganese Porphyrin The First Example of Polycarbonate Synthesis from 1-atm Carbon Dioxide. J. Polym. Set, Part A Polym. Chem. 2003, 41,3549-3555. 

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