Polycarbonates, synthesis with

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. 

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. 

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... 

The transesterfication process, shown in Eq. (11), is no longer practiced industrially because of the difficulty in producing a wide variety of polycarbonate resins with this process. As a result, the Schotten-Baumann synthesis currently dominates commercial production [5]. However, the transesterification process may experience a resurgence if nonphosgene routes to polycarbonates are commercialized because some of the nonphosgene chemistry under development takes advantage of the transesterification route. 

Stereoselective synthesis with carbon dioxide, including preparation of cyclic carbonates, polycarbonates, and oxazolidinone 13ASC2115. Strategies for spiroketal synthesis based on transition metal catalysis ... 

Although less frequently than with polyesters, it is possible to produce other polymers from ADMET polymerisation. Mecking and co-workers [44] described the synthesis of polyacetals and polycarbonates (PC) with a sparse and systematically varied density of functional groups generated by ADMET copolymerisation of unfunctionalised undeca-1,10-diene with bis(undec-10-en-l-yloxy)methane or di(undec-lO-en-l-yl) carbonate, followed by exhaustive hydrogenation (Scheme 5.10). 

Early developments in aliphatic and aromatic polycarbonates. The first significant documentation of aromatic polycarbonates synthesis began with Einhom [24]. He reacted hydroquinone, resorcinol, and catechol with phosgene in a pyridine solution, obtaining linear polymers from hydroquinone (an insoluble crystalline powder that melted above 280°C) and resorcinol (an amorphous material that melted with decomposition at 190 to 200°C), and a cyclic carbonate from catechol. Subsequent research was focused on finding more efficient preparation methods and on improving material properties [25]. 

Melt polymerization of bisphenols (bisphenol A, bisphenol P, bisphenol AF, and bisphenol Z) with diphenyl carbonate in CO2 with several catalysts have been achieved (91,92). Polymers with number-average molecular weights ranging from 2.2 X 10 to 1.1 X 10 g/mol M = 4.5 x 10 to 2.7 x 10 ) were obtained over a range of reaction temperatures (180-250°C) and CO2 pressures [20.7-24.1 MPa (207-241 bar)]. Reaction conditions were chosen to ensure efficient removal of solubilized condensate (phenol) without extracting the reactants (diphenyl carbonate). Polycarbonate synthesis from bisphenol A and diphenyl carbonate catalyzed by tetraphenylphosphonium tetraphenyl borate were also performed in SCCO2 (93) (eq. (9)). 

Almost a decade older than the wetting process of membrane pores is a technique whereby monomers are polymerized within the pores to form tubes. The first report by Martin et al. used a track-etehed polycarbonate membrane with 0.5 pm diameter linear pores. The pyrrole monomer solution and the chemical oxidant, an aqueous FeCU solution, diffused into the pores from opposite directions yielding poly(pyrrole) nanotubes. The same report also described the electrochemical synthesis of poly(pyrrole) nanotuhes using a polycarbonate membrane mounted onto a Pt-disk electrode. The length of the nanotubes obtained was identical to the membrane thickness (8 pm). 

Typical chemical systems are fast reactions between two difimctional monomers, AXA + BYB. The first monomer (diamine, bisphenolate) is dissolved in a water solution (in alkaline media in both cases), and the other monomer, with low water solubility (acid chloride, phosgene), is usually dissolved in an organic solvent. Either the neutral form of AXA is in an appreciable amount (in the case of amines), or a phase transfer catalyst is needed (as in polycarbonate synthesis), since ionized forms will not dissolve in the organic phase. A decrease in the pH is often used to quench interfacial polyamidation. 

In 1954 the surface fluorination of polyethylene sheets by using a soHd CO2 cooled heat sink was patented (44). Later patents covered the fluorination of PVC (45) and polyethylene bottles (46). Studies of surface fluorination of polymer films have been reported (47). The fluorination of polyethylene powder was described (48) as a fiery intense reaction, which was finally controlled by dilution with an inert gas at reduced pressures. Direct fluorination of polymers was achieved in 1970 (8,49). More recently, surface fluorinations of poly(vinyl fluoride), polycarbonates, polystyrene, and poly(methyl methacrylate), and the surface fluorination of containers have been described (50,51). Partially fluorinated poly(ethylene terephthalate) and polyamides such as nylon have excellent soil release properties as well as high wettabiUty (52,53). The most advanced direct fluorination technology in the area of single-compound synthesis and synthesis of high performance fluids is currently practiced by 3M Co. of St. Paul, Minnesota, and by Exfluor Research Corp. of Austin, Texas. 

Compared to polycarbonates, little work has so far been published on the synthesis of poly(iminocarbonates). The first attempted synthesis of a poly (iminocarbonate) was reported by Hedayatullah (44), who reacted aqueous solutions of various chlorinated dipheno-late sodium salts with cyanogen bromide dissolved in methylene chloride. Unfortunately, Hedayatullah only reported the melting points and elemental analyses of the obtained products which, according to Schminke (40), were oligomers with molecular weights below 5000. 

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... 

Enzymes are generally classified into six groups. Table 1 shows typical polymers produced with catalysis by respective enzymes. The target macromolecules for the enzymatic polymerization have been polysaccharides, poly(amino acid)s, polyesters, polycarbonates, phenolic polymers, poly(aniline)s, vinyl polymers, etc. In the standpoint of potential industrial applications, this chapter deals with recent topics on enzymatic synthesis of polyesters and phenolic polymers by using enzymes as catalyst. 

In an attempt to identify new, biocompatible diphenols for the synthesis of polyiminocarbonates and polycarbonates, we considered derivatives of tyrosine dipeptide as potential monomers. Our experimental rationale was based on the assumption that a diphenol derived from natural amino acids may be less toxic than many of the industrial diphenols. After protection of the amino and carboxylic acid groups, we expected the dipeptide to be chemically equivalent to conventional diphenols. In preliminary studies (14) this hypothesis was confirmed by the successful preparation of poly(Z-Tyr-Tyr-Et iminocarbonate) from the protected tyrosine dipeptide Z-Tyr-Tyr-Et (Figure 3). Unfortunately, poly (Z-Tyr-Tyr-Et iminocarbonate) was an insoluble, nonprocessible material for which no practical applications could be identified. This result illustrated the difficulty of balancing the requirement for biocompatibility with the need to obtain a material with suitable "engineering" properties. 

Boronic acids (69 and 70) (Fig. 45) with more than one boronic acid functionality are known to form a polymer system on thermolysis through the elimination of water.93 Specifically, they form a boroxine (a boron ring system) glass that could lead to high char formation on burning. Tour and co-workers have reported the synthesis of several aromatic boronic acids and the preparation of their blends with acrylonitrile-butadiene-styrene (ABS) and polycarbonate (PC) resins. When the materials were tested for bum resistance using the UL-94 flame test, the bum times for the ABS samples were found to exceed 5 minutes, thereby showing unusual resistance to consumption by fire.94... 

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... 

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