Synthesis of Polycarbonates

The carboxylation of epoxides may afford either monomers, as discussed above, or polycarbonates for example, Al-porphyrin complexes [175, 176] or Zn-compounds [177] promote the formation of polycarbonates. The pioneering studies of Inoue [178] and Kuran [179] have opened the route to the investigation of the copolymerization of CO2 and epoxides. The key issue here is to master the alternate insertion epoxide-C02. 

6 Reaction Mechanisms in the Direct Carboxylation of Alcohols, Polyols... 

Metal center Metals such as Al, Co, Cr, Mn, Zn, and Sn are active in the form of soluble complexes. A single site is necessary for catalysis to occur. In general such complexes have an octahedral structure with the active site at one of the axial positions. The trans ligand has an influence in labilizing the M-O or M-C bond and favoring the insertion 

Cyclic ether The facility of opening of the ring may speed the reaction. The structure of the ether is also important. An ethereal link in a linear structure behaves differently from alicyclic ethers 

Temperature Low temperatures in the range 298-330 K produce polymers, higher temperatures tend to form molecular cyclic carbonates 

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Synthesis of polycarbonates by Mipolynierization of carbon dioxide and glycidyl methacrylate using ionic liquids... 

In our previous work [8], we rqjorted the synthesis of (2-oxo-l,3-dioxolan-4-yl)methacrylate (DOMA) finrn carbon dioxide and glycidyl methacrylate (GMA) using quaternary salt catalysts. In the present work, we studied the catalytic pra rmance of alkyhnethyl imidazolium salt ionic liquid in the synthesis of polycarbonate from the copolyraerization of CO2 with GMA. The influences of copolymerization variable like catalyst structure and reaction tenperature on the conversion of GMA and the yield of the polycarbonate have been discussed. 

Synthesis of polycarbonates from glycidyl methacrylate and carbon dioxide with different... 

King, J.A. Jr. (2000). Synthesis of polycarbonates. In LeGrand, D.G., Bendler, J.T., editors. Handbook of Polycarbonate Science and Technology. Marcel Dekker, New York. 

The synthesis of polycarbonate of bisphenol A begins with the reaction of bisphenol A and sodium hydroxide to obtain the sodium salt of bisphenol A, as in Fig. 14.4.3. The sodium salt of bisphenol A is then reacted with phosgene to... 

Lipase CA catalyzed the polymerization of cyclic dicarbonates, cyclobis (hexamethylene carbonate) and cyclobis(diethylene glycol carbonate) to give the corresponding polycarbonates [105]. The enzymatic copolymerization of cyclobis(diethylene glycol carbonate) with DDL produced a random ester-carbonate copolymer. As to enzymatic synthesis of polycarbonates, reported were polycondensations of 1,3-propanediol divinyl dicarbonate with 1,3-propanediol [110], and of diphenyl carbonate with bisphenol-A [111]. 

The synthesis of polycarbonates from the alternating copolymerization of epoxides with C02 was first reported in 1969 using a ZnEt2/H20 mixture.954 Subsequent studies have focused upon a... 

Salen Metal Complexes as Catalysts for the Synthesis of Polycarbonates from Cyclic Ethers and Carbon Dioxide... 

But not only palladium(O) complexes can activate CO or O2, also palla-dium(II) complexes have been reported to be active in the presence of carbon monoxide or dioxygen as it was shown in the direct synthesis of polycarbonate from CO and phenol or bisphenol A [79,80]. The authors could confirm the positive influence of the NHC ligand comparing the activity and reactivity of the palladium-carbene complex with the corresponding PdBr2 catalyst. The molecular weights and yields of the polycarbonates improved with increasing steric hindrance of the substituents in the l,T-position of the car-bene complex. 

Research Focus Synthesis of polycarbonates, poly(acetal carbonate)s, poly(spiroacetal)s, polyesters, and polyurethanes using dihydroxyacetone. 

At our 1958 symposium, polycarbonate was introduced. Since then this polymer has reached a domestic production of 50 million pounds per year. J. T. Gregory, J. A. Cook, and A. B. Robertson report on the synthesis of polycarbonate oligomers useful in making random and block copolycarbonates. 

Scheme 1. Solvent-free synthesis of polycarbonate from bisphenol A and diphenyl carbonate [10].

Bisphenol A is manufactured by a reaction between phenol and acetone, the two products from the cumene hydroperoxide rearrangement. Bisphenol A is an important diol monomer used in the synthesis of polycarbonates and epoxy resins. 

These diols are also used for the synthesis of polycarbonates. Morgan [86] prepared the following polymers ... 

Eitan et al. (1) reported the synthesis of polycarbonate nanocomposites with untreated (as received) and epoxide treated nanocomposites. A 70% increase in the tensile modulus in the nanocomposites as compared to pure polymer with 5 wt% of the untreated nanotubes was observed as shown in Figure 2.12. However, this increase was increased to 95%, when same amount of epoxide treated nanotubes were used thus indicating the significance of interfacial interactions on the composite properties. 

Green chemistry offers the scientific option to deal with the problems associated with hazardous substances. An example is the alternative synthesis of polycarbonate, a polymer that has been commercially produced by the polycondensation between bisphenol-A and phosgene. The traditional synthesis is shown in Figure 12.2. Because phosgene is highly poisonous, a safer option is to use diphenyl carbonate as a non-toxic carbonylation reagent. See Figure 12.3 (Anastas and Williamson, 1996). 

Interfacial polycondensations can also be carried out in vapor-liquid systems. Reaction takes place at the interface between an aqueous solution of a bifunctional active hydrogen compound and the vapor of diacid chloride. Interfacial condensation is commercially important in the synthesis of polycarbonates (1-52). Polymerizations based on diacids are always less expensive than those that use diacid chlorides. In the polycarbonate case, however, the parent reactant, carbonic acid, is not suitable and the derived acid chloride, phosgene (COCI2), must be used. 

Polycarbonate synthesis by lipase-catalyzed polycondensation was demonstrated. Activated dicarbonate, 1,3-propanediol divinyl dicarbonate, was used as the monomer for enzymatic synthesis of polycarbonates.222 Lipase CA-catalyzed polymerization with a,co-alkylene glycols produced the polycarbonates with Mw up to 8.5 x 103. Aromatic polycarbonates with DP larger than 20 were enzymatically obtained from the activated dicarbonate and xylylene glycols in bulk.211... 

A number of novel process methods have been described. For example, ultrasound [1142] and phase-transfer catalytic techniques [1085] have been employed to Increase reaction rates in the synthesis of polycarbonates. 

Haba, O. Ueda, M. Kuze, S. Synthesis of polycarbonate from dimethyl carbonate and bisphenol-A through a non-phosgene process. J. Polym. Sci. A, Polym. Chem. 1999,37,2087-2093. 

The starting macromolecules can also be silanols, as, for instance, in a synthesis of polycarbonates. Preformed bis-silanols are used in this particular example ... 

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