Poly-condensation reactions

Mashraqui and coworkers have reported a three-component coupling of phenols, aromatic aldehydes and activated methylene substrates such as P-ketoesters, which under the influence of BF3 OEt2, give benzopyranyl product (159) in moderate yield (Equation 94) [96]. Attempts to effect the reaction with other Lewis acids gave complex mixtures. 

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Note Several condensing agents for the direct poly condensation reaction such as diphenyl chlorophosphate-LiBr and tosyl chloride-DMF have also been developed by Higashi et al.311,312 (see Section 2.3.3.2). 

The ring structures undergo further (poly)condensation reactions. These polymerization reactions proceed rapidly until particles with diameters of typically 1-2 nm are formed. Schematically, the process can be summarized as shown in Figure 3.15. 

Freeder, B. G. et al., J. Loss Prev. Process Ind., 1988, 1, 164-168 Accidental contamination of a 90 kg cylinder of ethylene oxide with a little sodium hydroxide solution led to explosive failure of the cylinder over 8 hours later [1], Based on later studies of the kinetics and heat release of the poly condensation reaction, it was estimated that after 8 hours and 1 min, some 12.7% of the oxide had condensed with an increase in temperature from 20 to 100°C. At this point the heat release rate was calculated to be 2.1 MJ/min, and 100 s later the temperature and heat release rate would be 160° and 1.67 MJ/s respectively, with 28% condensation. Complete reaction would have been attained some 16 s later at a temperature of 700°C [2], Precautions designed to prevent explosive polymerisation of ethylene oxide are discussed, including rigid exclusion of acids covalent halides, such as aluminium chloride, iron(III) chloride, tin(IV) chloride basic materials like alkali hydroxides, ammonia, amines, metallic potassium and catalytically active solids such as aluminium oxide, iron oxide, or rust [1] A comparative study of the runaway exothermic polymerisation of ethylene oxide and of propylene oxide by 10 wt% of solutions of sodium hydroxide of various concentrations has been done using ARC. Results below show onset temperatures/corrected adiabatic exotherm/maximum pressure attained and heat of polymerisation for the least (0.125 M) and most (1 M) concentrated alkali solutions used as catalysts. 

Hoftyzer and van Krevelen [100] investigated the combination of mass transfer together with chemical reactions in polycondensation, and deduced the ratedetermining factors from the description of gas absorption processes. They proposed three possible cases for poly condensation reactions, i.e. (1) the polycondensation takes place in the bulk of the polymer melt and the volatile compound produced has to be removed by a physical desorption process, (2) the polycondensation takes place exclusively in the vicinity of the interface at a rate determined by both reaction and diffusion, and (3) the reaction zone is located close to the interface and mass transport of the reactants to this zone is the rate-determining step. 

In the case of PBT, the CEG content of the prepolymer should not exceed 40meq/kg, or otherwise the poly condensation reaction is inhibited due to an increased formation of tetrahydrofuran (THF). The effect of the CEG content in a PBT prepolymer on the final IV is shown in Figure 5.20. 

Production of pol3rmers through poly-substitution or poly-condensation reactions would be expected to be a natural extension of simple PTC chemistry. To a large extent this is true, but as Percec has shown. Chapter 9, the ability to use two-phase systems for these reactions has enormously extended the chemist s ability to control the structure of the polymers produced. Kellman and co-workers (Chapter 11) have also extensively studied poly-substitution displacements on perfluorobenzene substrate to produce unique polymers. 

Bis(hydroxymethyl) furan and 5-hydroxymethyl furfural (available from C6 sugars) have been oxidized to furan-2,5-dicarboxylic acid (44)- Linear polyesters, polyurethanes, and polyamides containing these monomers have been described in the literature (45-43) and have been made via condensation polymerization techniques including bulk, solution, and interfacial mixing procedures. Gandini (5,34) reviewed the poly condensation reactions up to 1986 and... 

While catalysts are also used in the production of other types of polymers, the properties of most of these materials are not particularly dependent on the type of catalyst employed. Many poly condensation reactions, e. g. the formation of polyesters, polyamides or urea-formaldehyde resins, are speeded up by addition of some Bronsted or Lewis acids. Since relevant properties of these polymer products, such as their average chain lengths, are controlled by equilibrium parameters, primarily by the reaction temperatures and molar ratios of the monomers employed, and since their linkage patterns are dictated by the functional groups involved, addition of a catalyst has little leverage on the properties of the resulting polymer materials. 

Free radicals may also be intermediates in poly condensation reactions, in special cases, such as... 

As with interfacial polycondensation an acid-acceptor is necessary to neutralize the hydrochloric acid formed in the reaction. These low-temperature poly condensation reactions are irreversible, and the acid-acceptor is necessary only to keep the reacting diamine free for reaction with the acid chloride. iV,iV-Dimethylacetamide and related solvents are often employed. Ar,A-Dimethylformamide cannot be used as it reacts with the acid chloride, and only low-molecular-weight polymer results. These amide solvents form loose complexes with the hydrochloric acid produced during the polymerization, and no additional acid-acceptor is needed. However, the final solutions are usually neutralized to minimize corrosion of metallic equipment during later steps such as spinning, and to provide small amounts of water often found necessary for the long-term stability of the polymer solutions [111]. 

Variables Affecting Interfacial Poly condensation Reactions... 

The problem of anionic structure and the quantitative distribution of particles in silicate melts (see also in Chapter 2.1.9.) is discussed in several works. The simplest application of the Flory s (1953) polymer theory to silicate melts is the theory of linear and branched chains proposed by Masson (1965, 1968, 1977) and Masson et al. (1970). In this theory, it is assumed that the silicate anions are composed exclusively of linear and branched chains of the general formula Si 03 " j. These chains arise by poly-condensation reactions of the type... 

A special problem in the application of the polymer theory is the knowledge of the equilibrium constant of the poly-condensation reaction A n. The values of the dimerization constants in some binary Me0-Si02 systems (M = Ca, Mn, Pb, Fe, Co, Ni) were calculated by Masson (1977). Balta and Balta (1971) found a linear relationship between the logarithm of the equilibrium constant and the ionization potential of the metallic cation, which allows estimation of the equilibrium constant in systems, where the experimental data are missing, e.g. for cations with a ionization potential close to the second ionization potential of Mg, Masson (1977) published for Mn at 1773 K and Pb at 1273 K the values of the equilibrium constant Ku = 0.19 K and Ku = 0.196, respectively. 

Carbamide (urea-formaldehyde) resin is prepared by the poly condensation reaction of urea and formaldehyde in aqueous or aqueous-alcoholic medium. 

Scheme 1. HiC-Catalyzed Poly condensation Reactions between Diols and Diacids...

Interfacial and solution polycondensations are commercially important. For example, an unstirred interfacial poly condensation reaction is utilized in the production of polyamide fibers. Another important application of interfacial polycondensation is the enhancement of shrink resistance of wool. The wool is immersed first in a solution containing one of the reactants and subsequently in another solution containing the other reactant. The polymer resulting from the interfacial reaction coats the wool and improves its surface properties. 

The possibility of equilibrium process of chemical bonds association-dissociation should be also exluded, since for this process the value does not exceed 2.03 [58]. After t 48 min in system neither chemical nor physical changes occur, that is reflected by the conditions Q = const and const. The poly condensation reaction realization rate 0 can be obtained from the Eq. (27), differentiating it by time t. This gives the expression [113] ... 

Mikitaev, A. K. Korshak, V. V Musaev, Yu. I. Storozhuk, I. P. Correlation analysis of poly condensation reaction of disodium salts of bisphenols with 4,4 -dichlo-rodiphenylsulfone. In collection Problems of Physics-chemistry of Polymers. Ed. Mikitaev, A. Zelenev, Yu. Nal chik, KBSU, 1972,29-38. 

The term geopolymeric cements or geopolymers is not clearly defined. In general, they are inorganic cementitious systems in which a three-dimensional zeoUtic framework has been formed in a poly condensation reaction. 

Similar poly-condensation reactions can be carried out also with oxy-acids, amines and acids, urea or phenol and formaldehyde, etc. they yield in part chain and in part reticulate products, which have been discussed, particularly by W. H. Carothers and his collaborators. A more detailed description of such products will be given in another volume of this series (comp, also vol. I). The mechanism of such processes will likewise be discussed more extensively in another volume. 

In a recent paper [38], Munoz-Aguado and Gregorkiewitz reported the preparation of silica sols by neutralization of sodium silicate solution with HCl. They used " Si NMR to monitor the poly condensation reaction under acidic and basic pH. It was found that polycondensation sets in immediately after the reagents are mixed, as evidenced by the disappearance of the monometer (Q ) and a progressive continuous increase of the fraction of 4-connected silicate tetrahedra (Q" ) at the expense of Q and species (Fig. 6). However, for base-catalyzed reactions Q ... 

Chemical synthesis Poly condensation reaction of di-functional thiophene in presence of Ni catalysts Oxidative coupling reaction of bi-thiophene in presence of ferric chloride using AICI3, CUCI3 and organic solvents Plasma polymerization from 3-methyl thiophene or thiophene (1-6)... 

The results of experiment showed, that in the presence of synthetic graphite the viscosity of polymer increases this proves our earlier assumption, that selective adsorption leads to the increase of the local concentration of monomers on the surface of fillers and to the increase of poly condensation reaction speed. 

Reaction (1) shows the calcination of kaolin, which can also be described as a thermal dehydration process that destroys the original layered structure of the system. Reactions (2) and (4) describe the alkahne dissolution of metakaolin resulting in primary condensation structures (aluminosilicate oligomers), which, by further poly condensation reactions (3) and (5) in the alkaline environment, give rise to an infinite number of repeating units, thus resulting in a geopolymeric network [10]. The formation of the aluminosilicate structure was initially simply described as a series of destructive and condensation reactions ... 

Poly(butylene succinate) can be produced from a poly condensation reaction of succinic acid and butanediol in the presence of catalysts (Xu and Guo 2010). Poly(butylene succinate) can also be produced from biomass-based furfural that oxidized to fumaric acid. The fumaric acid can be hydrogenated under high pressure to produce 1,4-butanediol and succinic acid and then ultimately poly(butylene succinate) (Tachibana et al. 2010). 

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