Formation Of Polycarbonates Research Articles

Alternating copolymerization of carbon dioxide and epoxide by manganese porphyrin: The first example of polycarbonate synthesis from 1‐atm carbon dioxide

AbstractThe first successful example of the formation of polycarbonate from 1‐atm carbon dioxide and epoxide was demonstrated by the alternating copolymerization of carbon dioxide and epoxide with manganese porphyrin as a catalyst. The copolymerization of carbon dioxide and cyclohexene oxide with (porphinato)manganese acetate proceeded under the 1‐atm pressure of carbon dioxide to give a copolymer with an alternating sequence. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3549–3555, 2003

Hydrolytic Polycondensation of Bisphenol‐A‐Bischloroformate Catalyzed by Phase‐Transfer Catalysts

AbstractThe hydrolytic interfacial polycondensation of bisphenol‐A‐bischloroformate was performed with four different phase‐transfer (PT) catalysts: N‐butylpyridinium bromide, triethylbenzylammonium (TEBA) chloride, tetrabutylammonium hydrogen sulfate, and tetraphenylphosphonium bromide. These polycondensations were conducted at 5 or 35 °C initial reaction temperature. The resulting polycarbonates were characterized by viscosity and SEC measurements and by MALDI‐TOF mass spectrometry. The four PT catalysts gave quite different results with respect to molecular weight and formation of cyclic polycarbonates. The highest molecular weights (number average, $\overline M _{\rm n} \approx 215\;{\rm kDa}$ and weight average, $\overline M _{\rm w} \approx 600\;{\rm kDa}$) were obtained with TEBA‐Cl. Lower temperatures and high feed ratios of TEBA‐Cl proved to be favorable for both high molecular weights and high fractions of cycles. Cyclic polycarbonates were detectable in the mass spectra up to 14 kDa (technical limit of the measurements). Low molecular weights in combination with unreacted chloroformate groups proved that the other PT‐catalysts were less efficient under the given reaction conditions.MALDI‐TOF mass spectrum of the polycarbonate No. 3b.magnified imageMALDI‐TOF mass spectrum of the polycarbonate No. 3b.

Mechanistic aspects of the copolymerization reaction of carbon dioxide and epoxides, using a chiral salen chromium chloride catalyst.

The air-stable, chiral (salen)Cr(III)Cl complex (3), where H(2)salen = N,N'-bis(3,5-di-tert-butyl-salicylidene)-1,2-cyclohexene diamine, has been shown to be an effective catalyst for the coupling of cyclohexene oxide and carbon dioxide to afford poly(cyclohexenylene carbonate), along with a small quantity of its trans-cyclic carbonate. The thus produced polycarbonate contained >99% carbonate linkages and had a M(n) value of 8900 g/mol with a polydispersity index of 1.2 as determined by gel permeation chromatography. The turnover number (TON) and turnover frequency (TOF) values of 683 g of polym/g of Cr and 28.5 g of polym/g of Cr/h, respectively for reactions carried out at 80 degrees C and 58.5 bar pressure increased by over 3-fold upon addition of 5 equiv of the Lewis base cocatalyst, N-methyl imidazole. Although this chiral catalyst is well documented for the asymmetric ring-opening (ARO) of epoxides, in this instance the copolymer produced was completely atactic as illustrated by (13)C NMR spectroscopy. Whereas the mechanism for the (salen)Cr(III)-catalyzed ARO of epoxides displays a squared dependence on [catalyst], which presumably is true for the initiation step of the copolymerization reaction, the rate of carbonate chain growth leading to copolymer or cyclic carbonate formation is linearly dependent on [catalyst]. This was demonstrated herein by way of in situ measurements at 80 degrees C and 58.5 bar pressure. Hence, an alternative mechanism for copolymer production is operative, which is suggested to involve a concerted attack of epoxide at the axial site of the chromium(III) complex where the growing polymer chain for epoxide ring-opening resides. Preliminary investigations of this (salen)Cr(III)-catalyzed system for the coupling of propylene oxide and carbon dioxide reveal that although cyclic carbonate is the main product provided at elevated temperatures, at ambient temperature polycarbonate formation is dominant. A common reaction pathway for alicyclic (cyclohexene oxide) and aliphatic (propylene oxide) carbon dioxide coupling is thought to be in effect, where in the latter instance cyclic carbonate production has a greater temperature dependence compared to copolymer formation.

Polymer supported chromium porphyrin as catalyst for polycarbonate formation in supercritical carbon dioxide.

A new polymer-supported chromium porphyrin has been prepared and fully characterised; its catalytic activity and recyclability were investigated for the ring-opening copolymerisation of 1,2-cyclohexene oxide (CHO) and carbon dioxide (CO2).

Synthesis of polycarbonates by a silicon-assisted alkoxy/carbonylimidazolide coupling reaction

The investigation of a silicon-mediated coupling reaction between hydroxyl and carbonylimidazolide functional groups in the preparation of carbonate linkages is described. Application of this reaction to the formation of aliphatic polycarbonates was accomplished by the polymerization of an AB monomer unit, which was composed of 1,4-cyclohexanediol, where one of the hydroxyl groups was protected as a dimethylphenylsilyl ether and the other carried the carbonylimidazolide functionality. Reaction of this monomer with cesium fluoride removed the silicon protecting group and the resulting alkoxy anion promoted polymerization. Poly(1,4-cyclohexanecarbonate)s with typical molecular weights of Mw = 20,000 and Mn = 7300 a.m.u. (from GPC based upon polystyrene standards) were prepared in ca. 65% yield. The polymer showed a glass transition temperature at 138°C by DSC. TGA gave 85% mass loss between 275 and 350°C. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1133–1137, 1997.

Blends of polyamide 6 and bisphenol‐A polycarbonate. Effects of interchange reactions on morphology and mechanical properties

AbstractBlends of polyamide 6 (PA6) and polycarbonate (PC) were prepared in a Brabender mixer, at 240°C, applying long mixing time, for 45 min. It was observed that the morphology and the mechanical properties tend to resemble those of a homogeneous material as the mixing time and PA6 concentration increase. This is attributed to chemical reactions taking place between the two homopolymers. Acidolysis, amidolysis, and aminolysis, catalyzed by the terminals and the amide groups of the polyamide, should in principle be possible. Our results indicate that the aminolysis is the main process, inducing simultaneously scission of PC chains and formation of PC‐PA6 copolymer chains. The latter act as interfacial agents between incompatible PA6 and PC, improving the mechanical properties of PA6‐rich blends, in agreement with the predictions of some theoretical models assuming good phase interpenetration. © 1992 John Wiley & Sons, Inc.

Transesterification Chemistry, Low Temperature Reactions of O-Nithophenyl Carbonates

Abstract The application of o-nitrophenyl carbonate to preparation of aromatic carbonates and polycarbonates is described. The differences in reactivity of ortho- and para-nitrophenyl carbonates are elaborated. Reaction of o-nitrophenyl carbonate, bisphenol, and catalytic nucleophilic base affords clean formation of polycarbonates via trans-esterification at or below ambient temperatures.

4468483 Aromatic polyester polycarbonates from polyols derived from recycled polyethylene terephthalate

A novel class of aromatic polyester polycarbonates is described. The polycarbonates are made by reacting an alkylene carbonate with an aromatic polyester polyol over a polycarbonate formation catalyst such as potassium stannate. In turn, the polyol is made by esterifying a dibasic acid waste stream with an alkylene glycol to produce a polyester polyol which is subsequently used to transesterify recycled polyethylene terephthalate.

A New Route to Carbonate Monomers for Synthesis of Polycarbonates

A number of carbonates (RCH2)2CO3 (R=CH3, C2H5, CH2=CH, C3H7, C5H11, C6H5) have been synthesized by the reaction of alkali metal carbonates with corresponding halogen derivatives in the presence of activating agents such as crown ethers, polyglymes, polyamines, and triethylbenzylammonium chloride. The effects of various parameters (type of the halogen derivative, metal carbonate, activating agent, solvent and reaction time) on the reaction yield have been studied. The carbonates obtained were used as monomers in transesterification with diols and diphenols leading to the formation of polycarbonates. The polycarbonates obtained were characterized by means of IR spectroscopy and their intrinsic viscosity was determined.

Effect of triethylamine on the formation of polycarbonates from a bischloroformate and bisphenol in an organic solvent

An investigation has been made of the effect of triethylamine on the preparation of polycarbonates from bisphenols of different reactivity and the bischloroformate of propane, in an organic solvent. It was found that when triethylamine reacts with the bischloroformate in an organic solvent a complex is formed with a molar ratio of the reactants of 1 : 2, which is stable under the conditions of low temperature polycondensation and decomposes when the temperature is raised, to form amide derivatives of the bischloroformate. It is shown that in reaction of the bischloroformate with complexes of triethylamine and the bisphenols, formation of the polycarbonate occurs only by the base catalysed mechanism, but in reaction of the bisphenols with the triethylamine-bischloroformate complex it occurs by a combination of base and nucleophilic catalysis. It was found that the nature of the organic solvent has a decisive effect on the mechanism of the reaction and it is shown that η red of the polycarbonates increases as the polarity of the organic solvent is increased.

Synthesis of polycarbonate based on di-(4-hydroxyphenyl)methylphenylmethane in organic solvents

Polycarbonates (PC) are prepared mainly by phosgenization in pyridine medium, or on the interface of two immiscible solvents. One of the disadvantages of the latter method is that a large amount of low-molecular impurities (e.g. NaCl) are present; the latter are difficult to remove from the polycarbonate, and greatly impair both the thermal stability and the dielectric properties of the polymer. In the case of phosgenization in pyridine it is necessary to use large amounts of this solvent, and because of this difficulties are encountered in separating and purifying the PC. Papers recently published by a number of authors deal with the synthesis of polyesters novel method envisages the use of tertiary amines (catalyzing the polycondensation reaction) in amounts equal to or slightly less than the stoichiometric ratio of the reactants, and this method is free from the disadvantages inherent in the first two methods. However, only a very limited amount of information has been published in regard to the synthesis of PC by the method in question [3], and it is insufficient to give a clear idea of the chemism of the process. At the same time the reactions involved in the formation of PC by this method may be regarded as model reactions taking place homogeneously in organic solvents, and possibly occurring during the synthesis of PC on the interface. It should be noted that the high rate of the reaction and the presence of the interface make the problem of investigating the interfacial polycondensation process considerably more difficult.

Copolymerization of carbon dioxide and epoxide with organometallic compounds

AbstractAttempts to copolymerize carbon dioxide with epoxide led us to the first success in using carbon dioxide as a direct starting material for synthesizing high polymers. Some organometallic catalyst systems were found to catalyze the alternate copolymerization of carbon dioxide and epoxide, resulting in the formation of polycarbonates, the structures of which were confirmed with the aid of IR, NMR and elemental analysis. Diethylzinc‐water system produced a methanol insoluble aliphatic polycarbonate of much higher molecular weight than that produced by polycondensation. Thermal properties of the methanol insoluble polycarbonate were studied by differential thermal analysis and thermogravimetric analysis.

Studies on the Synthesis of Polycabonates. IV.

Fundamental experiments on the reaction for formation of polycarbonate were continued from the preceding experiment. On the basis of these results, the me chanisms for podyconolensation reactions were investigated. i. An addition of a strong alkali solution, such as caustic soda, into a solution of oligomer in methylene chloride caused mainly dehydrochlorination at the boundary of the solutions, polymer being yielded. And, a part of terminal group (-O.COCl) was decomposed into -OH by the interfacial reaction with caustic soda. ii. Monohydric alcohols were reacted with terminal -O?ECOCl group into -O?ECO OR at first, then it was converted into -OH by hydrolysis, polyconodensation reaction becoming difficult to proceed. iii. A part of bisphenol A remained participated directly in the polyconodensation and accordingly, the rate of condensation-polymeizatian and the max imum molecular weight were increased.

Studies on the Synthesis of Polycabonates. V

Fundamental experiments on the reaction for formation of polycarbonate were continued from the preceding experiment. On the basis of these results, the me chanisms for podyconolensation reactions were investigated. i. An addition of a strong alkali solution, such as caustic soda, into a solution of oligomer in methylene chloride caused mainly dehydrochlorination at the boundary of the solutions, polymer being yielded. And, a part of terminal group (-O.COCl) was decomposed into -OH by the interfacial reaction with caustic soda. ii. Monohydric alcohols were reacted with terminal -O?ECOCl group into -O?ECO OR at first, then it was converted into -OH by hydrolysis, polyconodensation reaction becoming difficult to proceed. iii. A part of bisphenol A remained participated directly in the polyconodensation and accordingly, the rate of condensation-polymeizatian and the max imum molecular weight were increased.