Polycarbonates polycondensation

Phosgene addition is continued until all the phenoHc groups are converted to carbonate functionahties. Some hydrolysis of phosgene to sodium carbonate occurs incidentally. When the reaction is complete, the methylene chloride solution of polymer is washed first with acid to remove residual base and amine, then with water. To complete the process, the aqueous sodium chloride stream can be reclaimed in a chlor-alkah plant, ultimately regenerating phosgene. Many variations of this polycarbonate process have been patented, including use of many different types of catalysts, continuous or semicontinuous processes, methods which rely on formation of bischloroformate oligomers followed by polycondensation, etc. 

PBT is produced by the transesterification of dimethyl terephthalate with 1,4-butanediol by means of a catalyzed melt polycondensation (19). PBT is also semicrystalline and is an extremely tough resin. Several commercial resins use a blend of PBT with another resin, such as PET, polycarbonate, or nylon. Typically, composites of PBT contain 20—30 vol % fiber glass. 

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... 

Polycarbonates have also been studied recently with regard to chemical heterogeneity. Polycarbonates are polycondensation products of phosgene and aliphatic or aromatic dihydroxy compounds. 

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]. 

Aromatic polycarbonates are currently manufactured either by the interfacial polycondensation of the sodium salt of diphenols such as bisphenol A with phosgene (Reaction 1, Scheme 22) or by transesterification of diphenyl carbonate (DPC) with diphenols in the presence of homogeneous catalysts (Reaction 2, Scheme 22). DPC is made by the oxidative carbonylation of dimethyl carbonate. If DPC can be made from cyclic carbonates by transesterification with solid catalysts, then an environmentally friendlier route to polycarbonates using C02 (instead of COCl2/CO) can be established. Transesterifications are catalyzed by a variety of materials K2C03, KOH, Mg-containing smectites, and oxides supported on silica (250). Recently, Ma et al. (251) reported the transesterification of dimethyl oxalate with phenol catalyzed by Sn-TS-1 samples calcined at various temperatures. The activity was related to the weak Lewis acidity of Sn-TS-1 (251). 

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 ... 

Polycarbonates are polyesters resulting from the polycondensation of carbonic anhydride (furnished by phosgene) and a bisphenol. 

Interfacially formed condensation polymers such as polyesters, polycarbonates, nylons, and PUs are typically formed on a microscopic level in a chain-growth manner largely because of the highly reactive nature of the reactants employed for such interfadal polycondensations. 

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. 

Isosorbide and equimolar amounts of various diols were polycondensed with diphosgene in p3ridine. Different bisphenols, l,3-bis(4-hydroxybenzyloxy)pro-pane, and 1,4-cyclohexane diol were used as comonomers [59]. In some cases, large amounts of cyclic oligo- and polycarbonates were formed. 

Cyclic carbonates are not commercially available and have to be synthesized prior to use. As a result, commercially available carbonates such as diethyl carbonate [55-57] or diphenyl carbonate [93] were evaluated in polycondensation reactions with diols to prepare polycarbonates since they allow a broader spectrum of polymers to be accessed. Unfortunately, polymerizations employing diethyl carbonate require the use of an excess diethyl carbonate [55]. Nevertheless, polymers with molecular weight of 40kDa were achieved within 16 h. Also, the polymerization of diphenyl carbonate with butane-1,4-diol or hexane-1,6-diol via the formation of a cyclic dimer produced polymers with molecular weights ranging from 119 to 339kDa [93]. 

Since the early days of polyurethane discovery, the technology has focused on isocyanate reactions with polyesters or polyethers. The differences will be discussed in later sections. These reactions are responsible for the growth of the polyurethane industry. The polyesters of interest to polyurethane chemists terminate in hydroxyl groups and are therefore polyols produced by the polycondensation of dicarboxyhc acids and polyols. An example is a polyol with a polycarbonate structure (Figure 2.3). 

Step Linear Polycondensation Polyamides Polycarbonate Polyesters Polyethers Polyimide Siloxanes... 

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. 

Polycarbonates are amorphous polymers with excellent handling properties. Their spectrum of applications ranges from baby bottles to compact discs. Most of the polycarbonate produced is generated by the polycondensation of bisphenol A with phosgene in a biphasic system (sodium hydroxide/dichloromethane). The solution of the polycarbonate product in dichloromethane is washed with water to remove the by-product NaCl. However, in this washing process some 20 g L 1 of the dichloromethane ends up dissolved in the aqueous phase. The dichloromethane must also be removed from the polycarbonate, which is not easy. This means that the polycarbonate will invariably contain some chlorinated impurities, which adversely affects the properties of the polymer. 

The carbonylation oxidative polycondensation of bisphenol, 2,2-bis(4-hydroxyphenyl)propane, with transition metal-based catalysts, which yields the respective aromatic polycarbonate, is of high potential interest [6] ... 

If this complex is sufficiently stable, then no further reaction occurs, and the polycondensation is obviated. However, as mentioned above, by using controlled monomer design, a variety of functionalised polymers (typical by with Mn = 10 000—30 000 and Mw/Mn = 2.0) can be synthesised polyethers [15,48 50], poly(thioether)s [48], polyesters [51,52], polycarbonates [53], polyketones [54], polysiloxanes [55-58], poly(carbosiloxane)s [59], poly(carbosilane)s [60], poly(carbodichlorosilane)s [61] and polymers with a conjugated % system [62]. 

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