Polyesterification reaction between

In the polyesterification process p is directly calculated from the carboxyl group titer. Results for the polyesterification reaction between diethylene glycol and adipic acid at 166° and 202°C are plotted in Fig. 3 in accordance with the third-order equation (8). For comparison purposes, the course of the non-polymer-forming reaction of diethylene glycol with the monobasic acid, caproic, is also shown. Eq. (8) is not obeyed from zero to 80 percent esterification [l/(l—p) =l to 25], as is shown by the curvature over this region. From 80 to 93 percent esterification the reaction appears to be third order. The non-polymerforming esterification of diethylene glycol with caproic acid (and other... 

The kinetics of polycondensation reactions might be expected to be similar to those found in condensation reactions of small molecules (evidence suggests that rate coefficients are independent of polymer size). Polyesterification reactions between dibasic carboxylic acids and glycols can be catalysed by strong acids. In the absence of added catalyst, it has been suggested that the acidic monomer should act as a catalyst, whereupon the rate of reaction should be given by... 

Consider the condensation polyesterification reaction between ethylene glycol, H0-(CH2)2-0H, and terephthalic acid, HOOC-Ph-COOH, each of which has an initial concentration of 1.0 mol/liter. Calculate the number average and weight average degrees of polymerization at 1, 5, and 20 hours. The forward reaction rate constant for the polymerization reaction is 10.0 liter/mol hr, and second-order, catalyzed kinetics can be assumed. 

While most of the kinetic relationships derived in the preceding sections have referred to polyesterification reactions between a dicarboxylic acid and a glycol, extension to other step-growth polymerizations of bifunctional monomers can be done in a straightforward manner. 

For the polyesterification reaction between diethylene glycol and adipic acid, calculate the number-average molecular weight of the polyester that is formed when the extent of reaction p is equal to 0.90. Note that, for condensation polymers that are synthesized from two reactants, half the average-molar-mass of the repeat unit is used to calculate the degree of polymerization. 

For the citrate method, the metal ions (MI) in the required stoichiometric ratio were dissolved in deionized water together with citric acid (CA MI molar ratios of 1, 2 or 3) and ethylene glycol (EG) (1 1 EG CA). The solution was heated at 60°C for homogenization and then the temperature was increased to 110°C in oil bath under constant stirring for 24 h to eliminate the excess water and accelerate the polyesterification reaction between CA and EG. As the polymerization reaction proceeded, a homogeneous sol was obtained and further heated at 110°C in an oven for 8 h to remove the excess of solvent, forming an intermediate resin. The resin was calcined at 750°C in the primary study and then at 900°C, for 10 h in flowing air. 

Table 3. Kinetic parameters of esterification and polyesterification reactions. - The listed values relate to the following cases Reactions where at least one of the two reactants is difunctional and reactions between two monofunctional reactants having more than 4 carbon atoms in their molecule. Table is in two parts Part 1 (page 99 to 122) for experimental conditions. Part 2 (page 122 to 142) for results and references. 

The use of silylated monomers is an interesting alternative method of aromatic polyester synthesis since the silylated gaseous by-products cannot participate in the reverse reaction, shifting polyesterification toward polymer formation. Reactions between silyl esters and acetates (Scheme 2.23) and reactions between silyl ethers and acid chlorides (Scheme 2.24) have been applied to the synthesis of linear265-267 and hyperbranched wholly aromatic polyesters202,268 269 (see Section 2.4.5.2.2). 

Solution reactions between diacid chlorides and diols or diphenols are carried out in THF or CH2C12 at —10 to 30°C in die presence of tertiary amines such as triethylamine or pyridine, which play a role of both reaction catalyst and HC1 acceptor (Scheme 2.26). This synthetic mediod is also termed acceptor-catalytic polyesterification.295-297 High-temperature solution reactions have also been reported for a number of less soluble, generally semicrystalline, aromatic polyesters.6 They yield high-molar-mass polyesters exhibiting good mechanical properties and thermal stability. 

Trifluoroacetic anhydride, which activates the polyesterification of 4-hy-droxybenzoic acid via the formation of a mixed anhydride,307 and 1,1 -carbonyldiimidazole308 were the first reported activating agents. The reaction between 1,1 -carbonyldiimidazolc and carboxylic acids proceeds through the formation of N-acylimidazolcs, which react with aliphatic diols in the presence of sodium ethoxide catalyst (Scheme 2.28). 

The kinetics of step polymerizations other than polyesterification follow easily from those considered for the latter. The number of different general kinetic schemes encountered in actual polymerization situations is rather small. Polymerizations by reactions between the... 

Measurements of dielectric properties have been used to monitor chemical reactions in organic materials for more than fifty years. In 1934, Kienle and Race 11 reported the use of dielectric measurements to study polyesterification reactions. Remarkably, many of the major issues that are the subject of this review were identified in that early paper the fact that ionic conductivity often dominates the observed dielectric properties the equivalence between the conductivity measured with both DC and AC methods the correlation between viscosity and conductivity early in cure the fact that conductivity does not show an abrupt change at gelation the possible contribution of orientable dipoles and sample heterogeneities to measured dielectric properties and the importance of electrode polarization at low frequencies. 

The equilibrium constant of polyesterification is typically equal to that of the analogous model reaction between monofunctional compounds. This can be explained by the proposition [3] that the reactivity of a functional end-group in any growing polymer chain is independent of the degree of polymerization or chain-length. There have been several experimental verifications of this theory. Thus the equilibrium constant for the reaction between dimethyl terephthalate (DMT) and ethylene glycol at 280°C was found [31] to be 4.9 under certain conditions. Under identical conditions, the equilibrium constant for the model reaction was 5.0. 

In the presence of an added catalyst such as p-toluenesulphonic acid, simple esterification reactions and polyesterification reactions are second order [48]. Thus the kinetics of the catalysed reaction of lauric acid and lauryl alcohol in a medium of lauryl laurate closely parallels those of the polymer-forming reaction between adipic acid and 1,10-dodecanediol in a medium of polyester product. Second-order rate coefficients for the two reactions were [35], respectively, 45x10 equiv kg" sec and 16 X 10" equiv kg" sec . 

Ester formation is a standard organic reaction between an alcohol and a carboxylic acid, which is an equilibrium reaction that has been shown to occur under catalysis by either acid or base. In polyesterification involving an organic acid, the substrate is itself the catalyst. It has been noted (Pilati, 1989) that, among the many reaction mechanisms, Scheme 1.1 is the most likely for acid-catalysed esterification, with the second reaction being the rate-determining step. 

Polyamide formation is entirely analogous to polyesterification and all of the earlier considerations apply. For polymers of the type AABB, nylon-6,6 is the best example. Thus poly(hexamethylene adipamide) is formed by the condensation reaction between hexam-ethylene diamine and adipic acid ... 

Thus, the polyesterification reaction mixture at any instance consists of various-sized diol, diacid, and hydroxyacid molecules. Any OH-containing molecule can react with any COOH-containing molecule. This is a general characteristic of step polymerization. A comparative account of the differences between step polymerization or condensation polymerization on the one hand and chain polymerization or addition polymerization (see Chapter 6) on the other hand is given in Table 5.1. 

The usual techniques of polyesterification, such as the solution31 or interfacial32 reaction between an aromatic acid chloride and bisphenol, are not applicable to the preparation of poly (phenyl esters) from hydroxybenzoic acids (prepared by an acid or phenyl ester exchange reaction of the acetate or phenyl ester of the acid33 ). 

The direct polyesterification reaction of diacids with glycols is the most important industrial synthetic route to polyester polyols. The second most important synthetic route is the transesterification reaction between dimethyl esters of dicarboxylic or dibasic acids (dimethyl adipate, dimethyl terephthalate, dimethyl carbonate or even polyethylene terephthalate) and glycols (reaction 8.2) [1, 3-8]. 

The synthesis of dimeric fatty acids is based on the reaction between a fatty acid with one double bond (oleic acid) and a fatty acid with two double bonds (linoleic acid) or three double bonds (linolenic acid), at higher temperatures in the presence of solid acidic catalysts (for example montmorillonite acidic treated clays). Dimerised fatty acids (C36) and trimerised fatty acids (C54) are formed. The dimer acid is separated from the trimeric acid by high vacuum distillation. By using fatty dimeric acids and dimeric alcohols in the synthesis of polyesters and of polyester polyurethanes, products are obtained with an exceptional resistance to hydrolysis, noncrystalline polymers with a very flexible structure and an excellent resistance to heat and oxygen (Chapter 12.5). Utilisation of hydrophobic dicarboxylic acids, such as sebacic acid and azelaic acid in polyesterification reactions leads to hydrolysis resistant polyurethanes. 

In our earlier study it was observed that second order kinetics was valid for polyesterification of ABA. It is assumed that in the present analysis the same mechanism is valid for homopolyesterification. For treating the second reaction it was assumed that the 4-acetoxybenzoic acid (ABA) monomers approach a PET homopolyester, followed by a reaction. This also can be treated as a second order reaction between a PET segment and an ABA oligomer. 

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