Aromatic polycarbonates

Liaw and Chang [a.345] reported on brominated fluorine-containing homopolycarbonates and copolycarbonates of varied unit ratio that were synthesised from 3,3, 5,5 -tetrabromobisphenol-AF and bisphenol-A polycondensed with trichloromethyl chloroformate using a phase-transfer catalyst at 25 °C. The homopolycarbonate based on tetrabromobisphenol-AF had the highest Tg at 205 °C. The TG cnrves show that the Tj of polycarbonates was in the range of 445-475 °C. The LOI of homopolycarbonates based on bisphenol-A and tetrabromobisphenol-AF were found to be 26 and 93, respectively. 

Investigations on the N,N -diphenyl-N,N -bis(3-methylphenyI)(l,l -biphenyl)-4,4 -diamine (TPD)/bisphenol-A polycarbonate system showed that the glass transition temperatnre of the polycarbonate was reduced significantly in the presence of the TPD [a.346]. The depression of the Tg was more pronounced in the case of the cyclohexyl polycarbonate, which was conformationally more restricted. This was related in part to the large rednction in the conformational energy of the TPD/cyclohexyl polycarbonate pair relative to that with 

PR Paragi-Vedanthi and M. Doble, Enzyme and Microbial Technology, 2011, 48, 

The study of the chemistry of the PE surface is very important as oxidised groups are more easily degraded by microorganisms and because oxidised groups modulate microbial attachment by increasing the hydrophilicity of the surface, which implies that PE degradation will be boosted if a more oxidised surface is used as a substrate. [8]. 

Microbial utilisation of this polymer is physically limited by its insolubility in aqueous media, lack of functional groups and high molecular weight. 

The range of microorganisms able to degrade PE is so far limited to 17 genera of bacteria and 9 genera of fungi [43]. 

Investigating the ability of fungi and Streptomyces strains to attack degradable PE, consisting of disposed PE bags containing 6% starch, scientists isolated 8 different 

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A reexamination of polycarbonate chemistry was carried out about 50 years after the first aromatic polycarbonates of resorcinol and hydroquinone were discovered. In independent investigations at Bayer AG and General Electric, it was discovered that the polycarbonates of BPA could be prepared (eq. 2). Unlike the ahphatic polycarbonates prepared earlier, which were either hquids or low melting sohds, the aromatic polycarbonates were amorphous sohds having elevated glass-transition temperatures. 

Table 3. Aromatic Polycarbonates Derived from Bisphenols...

Noncrystalline aromatic polycarbonates (qv) and polyesters (polyarylates) and alloys of polycarbonate with other thermoplastics are considered elsewhere, as are aHphatic polyesters derived from natural or biological sources such as poly(3-hydroxybutyrate), poly(glycoHde), or poly(lactide) these, too, are separately covered (see Polymers, environmentally degradable Sutures). Thermoplastic elastomers derived from poly(ester—ether) block copolymers such as PBT/PTMEG-T [82662-36-0] and known by commercial names such as Hytrel and Riteflex are included here in the section on poly(butylene terephthalate). Specific polymers are dealt with largely in order of volume, which puts PET first by virtue of its enormous market volume in bottie resin. 

The melt viscosity of a polymer at a given temperature is a measure of the rate at which chains can move relative to each other. This will be controlled by the ease of rotation about the backbone bonds, i.e. the chain flexibility, and on the degree of entanglement. Because of their low chain flexibility, polymers such as polytetrafluoroethylene, the aromatic polyimides, the aromatic polycarbonates and to a less extent poly(vinyl chloride) and poly(methyl methacrylate) are highly viscous in their melting range as compared with polyethylene and polystyrene. 

Aliphatic polycarbonates have few characteristics which make them potentially valuable materials but study of various aromatic polycarbonates is instructive even if not of immediate commercial significance. Although bisphenol A polycarbonates still show the best all-round properties other carbonic ester polymers have been prepared which are outstandingly good in one or two specific properties. For example, some materials have better heat resistance, some have better resistance to hydrolysis, some have greater solvent resistance whilst others are less permeable to gases. 

Although it is somewhat of an oversimplification, the polysulphones are best considered as a group of materials similar to the aromatic polycarbonates but which are able to withstand more rigorous conditions of use. Because of their higher price they are only considered when polycarbonates or other cheaper polymers are unsuitable. 

The specialty class of polyols includes poly(butadiene) and polycarbonate polyols. The poly(butadiene) polyols most commonly used in urethane adhesives have functionalities from 1.8 to 2.3 and contain the three isomers (x, y and z) shown in Table 2. Newer variants of poly(butadiene) polyols include a 90% 1,2 product, as well as hydrogenated versions, which produce a saturated hydrocarbon chain [28]. Poly(butadiene) polyols have an all-hydrocarbon backbone, producing a relatively low surface energy material, outstanding moisture resistance, and low vapor transmission values. Aromatic polycarbonate polyols are solids at room temperature. Aliphatic polycarbonate polyols are viscous liquids and are used to obtain adhesion to polar substrates, yet these polyols have better hydrolysis properties than do most polyesters. 

Oxidative carbonylation generates a number of important compounds and materials such as ureas, carbamates, 2-oxazolidinones, and aromatic polycarbonates. The [CuX(IPr)] complexes 38-X (X = Cl, Br, I) were tested as catalysts for the oxidative carbonylation of amino alcohols by Xia and co-workers [43]. Complex 38-1 is the first catalyst to selectively prepare ureas, carbamates, and 2-oxazolidinones without any additives. The important findings were the identity of the counterion and that the presence of the NHC ligand influenced the conversions. 2-Oxazohdinones were formed from primary amino alcohols in 86-96% yield. Complex 38-1 also catalysed the oxidative carbonylation of primary amines to ureas and carbamates. n-Propylamine, n-butylamine, and t-butylamine were transformed into the... 

Engineering polymers are often used as a replacement for wood and metals. Examples include polyamides (PA), often called nylons, polyesters (saturated and unsaturated), aromatic polycarbonates (PCs), polyoxymethylenes (POMs), polyacrylates, polyphenylene oxide (PPO), styrene copolymers, e.g., styrene/ acrylonitrile (SAN) and acrylonitrile/butadiene/styrene (ABS). Many of these polymers are produced as copolymers or used as blends and are each manufactured worldwide on the 1 million tonne scale. 

No. 30 Environmentally Benign Synthesis of Aromatic Polycarbonates. Summary of Lectures and Posters, http //www.gscn.net/event/meeting/summary.html... 

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). 

Bisphenols. See also Bisphenol A (BPA) aromatic polycarbonates derived from, 19 806-808t... 

Brunelle, D. J., Boden, E. P. and Shannon, T. G., Remarkably selective formation of macrocyclic aromatic carbonates versatile new intermediates for the synthesis of aromatic polycarbonates, J. Am. Chem. Soc., 112,569 (1990). 

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. 

Polycarbonates, both aliphatic and aromatic, have been prepared by the ring opening polymerization of cyclic monomers or oligomers [22], Cyclic monomeric precursors are more common in aliphatic polycarbonates, but because of steric reasons aromatic polycarbonates can only be prepared from cyclic oligomers. Both cationic and anionic initiators have been examined and anionic initiators appear to be more efficient. 

Membranes with very regular pores of sizes down to around 10 nm can be prepared by track-etching [10], and, in principle, those membranes can be used for the fractionation of macromolecules in solution. A relatively thin (<35 pm) polymer film (typically from polyethylene terephthalate)/PET/or aromatic polycarbonate/PC/) is first bombarded with fission particles from a high-energy source. These particles... 

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] ... 

As stated above, the carbonylation oxidative polycondensation of bisphenol in the presence of transition metal-based catalysts leads to aromatic polycarbonate [scheme (18)] [6]. The reaction of bisphenol (HOArOH, e.g. Ar = p-C6H4 CMe2—C6H4—), carried out under CO and O2 pressure in a chlorohydrocarbon solvent under anhydrous conditions, using a group 8 metal-based catalyst (e.g. a PdBr2 complex) and a redox catalyst (e.g. Mn(II) (benzoinoxime)2, L vMn) in the presence of a base (e.g. 2,2,6,6,N-pentamethylpiperidine, R3N), involves most probably the pathway shown schematically below ... 

Although only low molecular weight polycarbonates in modest yield have been obtained by this method, it represents an interesting non-phosgene route to aromatic polycarbonates. 

Chung JYJ, Mason JP (1996) Toughened aromatic polycarbonate containing silicone rubber powder as molding composition. US Patent 5556908... 

A related system permitted the synthesis of aromatic polycarbonates (PCs) via oxidative carbonylation [24] of a biphenol [25]. High yields ( 80%) with close to industrially useful molecular weight (Mn = 94 000) were obtained in this case (Scheme 5). 

The glass temperatures of all products fall within the range 130°-160 °C. The partially aromatic polycarbonate has a glass temperature of 150 °C. the partially aromatic PETP has a glass temperature of 75 °C. To determine the ratio of the aromatic to the aliphatic content, we assume four chain links for the benzene rings. Then the polycarbonate has the ratio aromatic/aliphatic links = 4 6, the polyester has a ratio 4 2, and the polyamides (Table I) have a ratio 4 10. Despite the lower aromatic content the glass temperatures of some of the amorphous polyamide are... 

The first secondary transition below Tg, the so called fj-relaxation, is practically important. This became evident after Struik s (1978) finding that polymers are brittle below Tp and establish creep and ductile fracture between Tp and Tg. The p-relaxation is characteristic for each individual polymer, since it is connected with the start of free movements of special short sections of the polymer chain. In view of more recent data of Tp Boyer s relation, Eq. (6.29), is very approximate and fails completely for amorphous polymers with high Tg s (e.g. aromatic polycarbonates and polysulphones). Some rules of thumb may be given for a closer approximation. 

According to Eq. (4.3), the slope of the straight line obtained from a plot of the LOI versus the coke yield during pyrolysis or combustion of a polymer may be a measure of the ability of coke to improve the flame retardancy of polymers. Fig. 15 demonstrates that, when siloxane monomers are introduced into aromatic polycarbonates, the flame retardant effect of the coke increases considerably as compared with polymers not containing such monomers. It has been noted, however... 

Volatile production occurs from polycarbonate by entirely thermal decomposition between 450 and 550°C yielding about 25% solid residue as well. The pyrogram of the most common aromatic polycarbonate, poly(bisphenol A carbonate) is displayed in Figure 12.10. Alkylphenols and phenol are the main constituents of the boiling range 180-250°C and... 

Transesterifications of aliphatic carbonate esters with glycols are catalysed by alkali metal alkoxides. No catalyst is needed for the transesterification of diaryl carbonates with aliphatic diols. Alkyl carbonate esters and p-xylylene glycol undergo transesterification reactions when certain titanium compounds are used as catalysts. The preparation of aromatic polycarbonates by transesterification is best... 

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... 

Kricheldorf, H. R. Lubbers, D., Polymers of carbonic acid, 1. Synthesis of thermotropic aromatic polycarbonates by means of bis(trichloromethyl) carbonate, Makromol. Chem. Rapid Commun. 1989, 10, 383-386. 

The most practical nonphosgene process for manufacturing polycarbonates is the transesterification of diphenylcarbonate (DPC) with bisphenol-A. A nonphosgene process for the melt polymerization production of aromatic polycarbonates [reaction (14)], making use of EniChem technologies for the production of DMC and DPC as intermediates, has been commercially established and will account in a short time for about 300,000 ton/yr polycarbonates. 

The DMC-based route to aromatic polycarbonates takes place via production of DPC as intermediate and successive melt polymerization between DPC and bisphenol-A, overcoming the previous technology, based on interfacial polymerization with phosgene. 

Schnell, H. Bottenbruch, L. Krimm, H. Thermoplastic Aromatic Polycarbonates and Their Manufacture. US Patent 3,028,365, April 3, 1962. 

Hedges, V. Randomly Branched Aromatic Polycarbonate from Triphenol US Patent 4,415,723, November 15, 1983. 

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