Carbon polymerization

The Fischer-Tropsch process can be considered as a one-carbon polymerization reaction of a monomer derived from CO. The polymerization affords a distribution of polymer molecular weights that foUows the Anderson-Shulz-Flory model. The distribution is described by a linear relationship between the logarithm of product yield vs carbon number. The objective of much of the development work on the FT synthesis has been to circumvent the theoretical distribution so as to increase the yields of gasoline range hydrocarbons. 

Poly(glycolide-co trimethylene carbonate). Another successful approach to obtaining an absorbable polymer capable of producing flexible monofilaments has involved finding a new type of monomer for copolymerization with glycoHde (42). Trimethylene carbonate polymerized with glycoHde is shown below ... 

In addition to the formation of hydroperoxides, other reactions are known to occur simultaneously. The formation of polyperoxides, carbon-to-carbon polymerization, and the formation of epoxides and cyclic peroxides have been proposed or demonstrated in lipid oxidation. 

Alkynylmetal reagents, in i/>-hydridized carbon polymerization, 11, 673 Alkynyl(methoxy)borates, preparation, 9, 212 Alkynyl oligosilanes, preparation, 3, 433 Alkynylsilanes... 

Alkynyltin reagents applications, 9, 360 in Sonogashira coupling, 11, 18 in i/ -hydridized carbon polymerization, 11, 674-675 Alkynyltriphenylbismuthonium salts, in G—heteroatom bond formation, 9, 450... 

They consist of a thin layer (<10 fxm) of a nanoporous (3-1OA) carbon film supported on a meso-macroporous inorganic solid (alumina) or on a carbonized polymeric structure [15]. They are produced by pyrolysis of polymeric films. The following two types of membranes are produced ... 

In RPC systems, the retention is weaker on weakly or moderately polar stationary phases such as on phenyl- or cyanopropyl-bonded phases than on an alkylsilica phase. RPC separations on phenyl or cyanopropyl columns may show selectivities differing from those observed on Cix or Cs phases, but their main advantage is lower concentration of organic solvent required to elute weakly polar samples, which may potentially reduce the separation time. For the great majority of samples, however, the selectivity of separation is generally better on alkylsilica-bonded phases. On the other hand, retention of hydrophilic samples can be increased and their separation improved on columns with a high amount of bonded carbon (polymeric bonded phases) or on hydrophobic organic polymeric materials such as styrene-divinylbenzene copolymers. 

The nanoporous carbon membrane consists of a thin layer (<10pm) of a nanoporous (3-7 A) carbon film supported on a meso-macroporous solid such as alumina or a carbonized polymeric structure. They are produced by judicious pyrolysis of polymeric films. Two types of membranes can be produced. A molecular sieve carbon (MSC) membrane contains pores (3-5 A diameters), which permits the smaller molecules of a gas mixture to enter the pores at the high-pressure side. These molecules adsorb on the pore walls and then they diffuse to the low-pressure side of the membrane where they desorb to the gas phase. Thus, separation is primarily based on differences in the size of the feed gas molecules. Table 7 gives a few examples of separation performance of MSC membranes. ° Component 1 is the smaller component of the feed gas mixture. 

Graphitized carbon polymeric sorbents (styrene-divinylbenzene)... 

This ratio may also be estimated from a deteimination of the amount of initiator residues found in the monomer. From such data the significance of degradative chain-transfer in an allyl ester polymerization can be judged. For example, it was found that in the allyl ethyl carbonate polymerization, degradative chain-transfer predominates, whereas in the polymerization of allyl laurate and allyl benzoate, effective chain-transfer predominates [19]. 

Adsorption has been playing an increasingly important role in environmental control. The sorbents being nsed in common industrial adsorption systems for the removals of SO2 and volatile organic compounds (VOCs) are qnite weU-estabUshed. The VOC removal systems often use activated carbon, polymeric resins, and hydrophobic zeolites, for both gas and aqueous systems. Activated carbon (and alkalized forms) and hydrophobic zeolites are used for SO2 removal. Lime injection is used for SO2 removal from hot gases. For NO removal, on the contiary, no suitable sorbents have been established. For this reason, selective sorbents for NO remain an active research area, and will be discussed. The search for CO2 sorbents is also of interest. The subject of CO2 sorbents has been discussed recently in an excellent review by Yong et al. (2002) and will not be covered here. 

In the LiPFe salt and organic carbonates containing electrolytes, the SEI film is a passivating surface film on the anode (e.g., a graphite particle) consisting of Li-alkyl-carbonates, polymeric carbonates, and lithium fluoride and is formed on the surface of particles via either the direct decomposition of the solvents to form a precipitate layer, or the co-intercalation of solvated lithium ions and their decomposition beneath the surface in the initial stage of lithium intercalation (exfoliation), during the first few cycles. 

Dimethyl sulfoxide is generally favored, particularly with processes using sodium hydroxide as base. In carbonate polymerizations, the presence of free phenolic hydroxyl groups at polymerization temperatures of 150-160°C leads to undesirable side reactions Involving acid catalyzed decomposition of OMSO which ultimately can lead to stoichiometry upsets. For polymerizations involving carbonate, dimethyl acetamide is often the solvent of choice [7], DMSO is limited by its 180 C boiling point to temperatures of 170 C or lower while DMAc is useful in the 150-160 C range. 

Venner, J.G. and Ko, Y.S., US Patent 4,938,941, Partially Carbonized Polymeric Fibrous Material having an Electrical Resistivity of Enhanced Stability , 1990. 

The formation processes of metal-containing nanostructures in carbon or carbon-polymeric shells in nanoreactors can be related to one t) e of reaction series using the terminology of the theory of linear dependencies of free energies (LFE) [16]. Then it is useful to introduce definite critical values for the volume, surface energy of nanoreactor internal walls, as well as the temperature critical value. When the ration Ig k/k is proportional -AAF/RT, the ratio WAV can be transformed into the following expression ... 

Detailed investigations of the mechanism of five-membered cyclic carbonate polymerization initiated with tin and zirconium alkoxides were carried out by Kricheldorf et... 

A haloalkyl carbonate structure is formed by the initial ring-opening reaction of the monomer with alkyl halide, which was shown by using ethyl 3-iodopropyl carbonate as the initiator for cyclic carbonate polymerization. The obtained polymer contained both ethyl and iodopropyl end-groups. 

Macroinitiators such as polymeric Li, Na, and K alkoxides can also be used for the initiation of the six-membered cyclic carbonate polymerization. Thus, besides living vinyl polymers, hydroxyl group-terminated polymers of poly (tetrahydrofuran) (PTHF), poly(oxyethylene), and poly(dimethylsiloxane) (PDMS) were transformed to alkoxides by treatment with scc-BuLi or K-naphthalene and used as initiators. The use of these macroinitiators enables the identification of side reactions, as shown by Keul and Hocker for polystyrene lithium (PS Li ). The addition of the macro initiator to the monomer, to maintain a high excess of monomer, minimizes side reactions. Transformation of the polystyryl... 

Anionic metal-free initiation was successfully applied to both aliphatic and aromatic cyclic carbonates. This method is based on the reaction of a silyl ether with fluoride anions, for example, tetrabutyl ammonium fluoride (BU4NF) or tris (dimethylamino)sulfonium trimethylsilyl difluoride (TASF, [(CH3)2N]3 SSi(CH3)3p2), to produce an anion with a tetrabutyl ammonium or tris(dimethylamino)sulfonium counterion. The metal-free system is an efficient initiator for neopentyl carbonate polymerization. ... 

Darensbourg s group and Yang et al. have reported the use of effective salen complexes of aluminum as catalysts for six-membered cyclic carbonate polymerization. ... 

According to the second method of carbonate block copolymer synthesis, sequential monomer polymerization is proceeded with transformation of the active center. The block copolymers are prepared in three steps. First, the polymerization of one monomer is carried out. After complete conversion of the first monomer the transformation of active centers is performed, and the initiation of the polymerization of the second monomer is proceeded. For example, this approach was applied for obtaining poly(styrene-l7-neopentyl carbonate).After completion of the styrene living polymerization, carbanionic centers were transformed into alkoxide ones via reaction with EO and then the ROP of neopentyl carbonate polymerization was performed. In the case of block copolymers of methyl methacrylate with neopentyl carbonate living PMMA, prepared according to GTP, was used as a macroinitiator for DTC polymerization. A silyl keteneacetal active center was transformed to an alkoxide one. Depending on the functionality of the macroinitiator (A) used for cyclic carbonate polymerization, two types of block copolymers can be obtained A-B or B-A-B. 

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