Epoxide polymers catalysts

Bacskai, R Polymerization of Alicyclic Epoxides with Aluminium Alkyl Catalysts. J. Polymer Sci. A 1, 2777 (1963). 

The formation of epoxide polymers with a very high molecular weight by the discussed catalysts containing associated multinuclear species (— Zn-0— Zn O >) indicates that only a small fraction of the metal species in the catalyst is effective for the polymerisation. The broad molecular weight distribution of polymers yielded by these catalysts corresponds to the existence of various active sites [30]. 

To obtain a heat and water resistant crosslinked polymer, Cu naphthenate and an alcohol (e.g. benzyl alcohol) were added to BPA/DC as a catalyst epoxide resins (cf. Sect. 6) can be used as well [19]. The use of Zn acetate together with dicumyl peroxide was also mentioned [20],... 

Chiral Co(III)-salen complexes can also serve as efficient catalysts for HKR of terminal epoxides. Polymer-supported chiral salen complexes 156 were prepared from chiral Co complex 154 and ethylene glycol dimethacrylate 155, as shown in Scheme 3.45. The chemical reduction of 156, followed by treatment with acetic acid under aerobic conditions, produced the catalytically active polymer 157, which was used in the HKR of propylene oxide [87]. Some other examples of polymeric salen-Co complexes have also been reported for the same reaction [88, 89]. 

Though the gas number of ABFA is normally 220-260 cm /g, it can go up to 420 cm /g in the presence of catalysts. Azodicarbonamide is recommended for foaming of PVC, polyolefins, polyamides, polysiloxanes, epoxides, polymers and compolymers of acrylonitrile and acrylates, and rubbers. 

To highlight the selectivity of metal-catalyzed epoxidation, Nicol and coworker reported the epoxidation of PBD and PIP using Bu OOH and molybdenum complex. Previous studies reported very high selectivity of epoxidation for backbone C=C bonds over pendant C=C bonds. As a result, when diene-containing polymers with >98% cis-1,4 units were used, complete epoxidation of aU C=C bonds was achieved. However, it was noted that HCl was generated during the reaction and the failure to remove it led to cross-linking of the epoxidized polymer. Additionally, appreciable amounts of the molybdenum catalyst remained in the polymer after workup. 

Thermosetting Reactive Polymers. Materials used as thermosetting polymers include reactive monomers such as urea—formaldehyde, phenoHcs, polyesters, epoxides, and vinyls, which form a polymerized material when mixed with a catalyst. The treated waste forms a sponge-like material which traps the soHd particles, but not the Hquid fraction the waste must usually be dried and placed in containers for disposal. Because the urea—formaldehyde catalysts are strongly acidic, urea-based materials are generally not suitable for metals that can leach in the untrapped Hquid fractions. Thermosetting processes have greater utiHty for radioactive materials and acid wastes. 

In 1957, it was discovered that organometaUic catalysts gave high mol wt polymers from epoxides (3). The commercially important, largely amorphous polyether elastomers developed as a result of this early work are polyepichlorohydrin (ECH) (4,5), ECH—ethylene oxide (EO) copolymer (6), ECH—aUyl glycidyl ether (AGE) copolymer (7,8), ECH—EO—AGE terpolymer (8), ECH—propylene oxide (PO)—AGE terpolymer (8,9), and PO—AGE copolymer (10,11). The American Society for Testing and Materials (ASTM) has designated these polymers as follows ... 

Ethylene oxide, the simplest epoxide, is an intermediate in the manufacture of both ethylene glycol, used for automobile antifreeze, and polyester polymers. More than 4 million tons of ethylene oxide is produced each year in the United States by air oxidation of ethylene over a silver oxide catalyst at 300 °C. This process is not useful for other epoxides, however, and is of little value in the laboratory. Note that the name ethylene oxide is not a systematic one because the -ene ending implies the presence of a double bond in the molecule. The name is frequently used, however, because ethylene oxide is derived pom ethylene by addition of an oxygen atom. Other simple epoxides are named similarly. The systematic name for ethylene oxide is 1,2-epoxyethane. 

Extensive studies of stereoselective polymerization of epoxides were carried out by Tsuruta et al.21 s. Copolymerization of a racemic mixture of propylene oxide with a diethylzinc-methanol catalyst yielded a crystalline polymer, which was resolved into optically active polymers216 217. Asymmetric selective polymerization of d-propylene oxide from a racemic mixture occurs with asymmetric catalysts such as diethyzinc- (+) bomeol218. This reaction is explained by the asymmetric adsorption of monomers onto the enantiomorphic catalyst site219. Furukawa220 compared the selectivities of asymmetric catalysts composed of diethylzinc amino acid combinations and attributed the selectivity to the bulkiness of the substituents in the amino acid. With propylene sulfide, excellent asymmetric selective polymerization was observed with a catalyst consisting of diethylzinc and a tertiary-butyl substituted a-glycol221,222. ... 

The preferred catalysts are salts of inorganic and organic acids as well as tertiary amines. Phthalic anhydride, succinic anhydride and maleic anhydride are typical acid anhydrides, while ethylene oxide, propylene oxide, epichlorohydrin and phenyl glycidyl ether are typical epoxides. The synthesis of a ladder polymer was carried out by using bisanhydrides264. ... 

Allylic alcohols can be converted to epoxy-alcohols with tert-butylhydroperoxide on molecular sieves, or with peroxy acids. Epoxidation of allylic alcohols can also be done with high enantioselectivity. In the Sharpless asymmetric epoxidation,allylic alcohols are converted to optically active epoxides in better than 90% ee, by treatment with r-BuOOH, titanium tetraisopropoxide and optically active diethyl tartrate. The Ti(OCHMe2)4 and diethyl tartrate can be present in catalytic amounts (15-lOmol %) if molecular sieves are present. Polymer-supported catalysts have also been reported. Since both (-t-) and ( —) diethyl tartrate are readily available, and the reaction is stereospecific, either enantiomer of the product can be prepared. The method has been successful for a wide range of primary allylic alcohols, where the double bond is mono-, di-, tri-, and tetrasubstituted. This procedure, in which an optically active catalyst is used to induce asymmetry, has proved to be one of the most important methods of asymmetric synthesis, and has been used to prepare a large number of optically active natural products and other compounds. The mechanism of the Sharpless epoxidation is believed to involve attack on the substrate by a compound formed from the titanium alkoxide and the diethyl tartrate to produce a complex that also contains the substrate and the r-BuOOH. ... 

The final resin product is obtained by reacting (curing or crosslinking) the above di-epoxide with acid anhydrides or polyamines. The curing agents (sometimes incorrectly called catalysts) react with the three-membered epoxide rings to produce a highly crosslinked polymer. 

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