Polycondensation polycarbonate synthesis

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... 

See also PBT degradation structure and properties of, 44-46 synthesis of, 106, 191 Polycaprolactam (PCA), 530, 541 Poly(e-caprolactone) (CAPA, PCL), 28, 42, 86. See also PCL degradation OH-terminated, 98-99 Polycaprolactones, 213 Poly(carbo[dimethyl]silane)s, 450, 451 Polycarbonate glycols, 207 Polycarbonate-polysulfone block copolymer, 360 Polycarbonates, 213 chemical structure of, 5 Polycarbosilanes, 450-456 Poly(chlorocarbosilanes), 454 Polycondensations, 57, 100 Poly(l,4-cyclohexylenedimethylene terephthalate) (PCT), 25 Polydimethyl siloxanes, 4 Poly(dioxanone) (PDO), 27 Poly (4,4 -dipheny lpheny lpho sphine oxide) (PAPO), 347 Polydispersity, 57 Polydispersity index, 444 Poly(D-lactic acid) (PDLA), 41 Poly(DL-lactic acid) (PDLLA), 42 Polyester amides, 18 Polyester-based networks, 58-60 Polyester carbonates, 18 Polyester-ether block copolymers, 20 Polyester-ethers, 26... 

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]. 

Polycondensation of Bisphenols, II, with Phosgene. Polycondensation of siloxane-linked bisphenols, II, with phosgene is the most obvious synthetic approach leading to siloxane-modified poly(arylene carbonates) since the phosgene-bisphenol polycondensation is used in the synthesis of aromatic polycarbonates (1). This method was used initially to prepare polymer (as indicated in reaction 1) as well as for the attempted synthesis of polymers 2 and 5 ... 

Homopolycarbonates based on 1 and 2 have been prepared by several groups. The interfacial polycondensation typical for the synthesis of aromatic polycarbonates is not useful with alditols, including 1, because they are water-soluble and less acidic than diphenols. The 1-based homopolycarbonate was prepared by phosgena-tion of the sugar diol, with phosgene or diphosgene in pyridine-containing solvent mixtures at low temperatures. The polycondensation of the isosorbide bischloro-formate in pyridine is an alternative approach. 

Several review articles on biodegradable polymers and polyesters have appeared in the literature [12-22]. Extensive studies have been carried out by Al-bertsson and coworkers developing biodegradable polymers such as polyesters, polyanhydrides, polycarbonates, etc., and relating the structure and properties of aliphatic polyesters prepared by ROP and polycondensation techniques. In the present paper, the current status of aliphatic polyesters and copolyesters (block, random, and star-shaped), their synthesis and characterization, properties, degradation, and applications are described. Emphasis is placed primarily on aliphatic polyesters derived by condensation of diols with dicarboxylic acids (or their derivatives) or by the ROP of cyclic monoesters. Polyesters derived from cyclic diesters or microbial polyesters are beyond the scope of this review. 

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. 

Okamoto [289] synthesized identical macromonomers that had been poly-condensed with prepolycarbonates, obtaining polycarbonatc-gra/f- PMMA. The PMMA grafting chain brings transparency and toughness to polycarbonate matrices. Other authors used this technique to synthesize dihydroxy PS macromonomers, used in the synthesis of polyester by polycondensation with terephtalic acid and butylene glycol. 

Rodney, R.L., Allinson, B.T., Beckman, E.J., and Russell, A.). (1999) Enzyme-catalyzed polycondensation reactions for the synthesis of aromatic polycarbonates and polyesters. Biotechnol. Bioeng., 65 (4), 485-489. 

Classification by Decomposition Behavior. The decomposition mechanism is a reasonable way to classify polymers. They can either depolymerize upon irradiation, for example, poly(methylmethacrylate), or decompose into fragments such as poly-imides or polycarbonates. This method of classification is closely related to the synthesis of polymers. Polymers that are produced by radical polymerization from monomers, which contain double bonds, are likely to depolymerize into monomers, while polymers that have been formed by reactions like polycondensation will not depolymerize into monomers upon irradiation, but will be decomposed into different fragments. The second group cannot be used to produce films with the same structure or molecular weight as the original material with methods such as PLD. 

Table 13.3.16. Synthesis of aliphatic polysulfide Several polycarbonates were X in various organic soivent-water system with synthesized by two-phase DC-18-C-6 cataiyst polycondensation of bisphenols and...

The polycondensation of a diol and the diester of a dicarboxylic acid (e.g., the dimethyl ester) can be carried out in the melt at a considerably lower temperature than for the corresponding reaction of the free acid. Under the influence of acidic or basic catalysts a transesterification occurs with the elimination of the readily volatile alcohol (see Example 4.3). Instead of diesters of carboxylic acids one can also use their dicarboxylic acid chlorides, for example, in the synthesis of high-melting aromatic polyesters from terephthaloyl dichloride and bisphenols. The commercially very important polycarbonates are obtained from bisphenols and phosgene, although the use of diphenyl carbonate as an alternative component is of increasing interest (see Example 4.4). Instead of free acids, cyclic carboxylic... 

Zhu, W., et al. 2011. High-molecular-weight aliphatic polycarbonates by melt polycondensation of dimethyl carbonate and aliphatic diols synthesis and characterization. Polymer International 60(7) 1060-1067. 

A very active and fruitful area of research is the use of lipases for the synthesis of polyesters, polylactones, and polycarbonates (35). Many creative reactions have been devised. In this book, lipase-catalyzed polycondensation of diols/diacids was reported separately by Mahapatro et al (25), Kulshrestha et al... 

Growing importance of BPA as the chemical intermediate is particularly connected with rapidly expanding fields of polycarbonates and epoxy resins. Presently, the main market for BPA is in production of the polycarbonates (66% of the BPA in global production capacity), and the primary commercial method for their synthesis is a homogeneous (usually in pyridine) or an interfacial polycondensation of BPA with phosgene as shown in Figure 7.13. 

The enzymatic synthesis of polycarbonate was first reported in 1989 [133]. Lipase CR catalyzed the polycondensation of carbonic acid diphenyl ester with bisphenol-A in an aqueous acetone to give an oligocarbonate with a molecular weight of 900. 

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