Polycondensation in Solution

The polycondensation in solution method was also the method applied for the synthesis of poly(l,4-cyclohexylenedimethylene succinate) PCDS referred before (18). The molecular weight of the polymer increased with the boiling point of the solvent employed so highest molecular weights were achieved in n-decane at 215 °C with l-chloro-3-hydroxy-l,l,3,3-tetrabutyldistannoxane as catalyst. 

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With appropriate precautions, condensation and addition polymerization reactions can be carried out in the same apparatus as customarily used for organic preparative work (see Sects. 4.1 and 4.2). In order to obtain high molecular weights by polycondensation in solution, a special circulation apparatus can be advantageously used with advantage (Fig. 2.4). 

Polycondensation of diols with dicarboxylic acids is often performed in the melt. However, it does not always lead to high-molecular-weight polyesters. Sometimes, the starting materials or the resulting polyester are thermally unstable at the high condensation temperatures. If the reactants and the polyester are well soluble, one can carry out the polycondensation in solution (see Example 4-2). The elimination of water from diols and dicarboxylic acids frequently occurs rather slowly. In such cases suitable functional derivatives of the diols and dicarboxylic acids (esters or anhydrides) can be used instead of the direct condensation, as described in Sect. 4.1.1.3. 

Galbis and Munoz-Guerra et al. used the secondary G-protected L-threitol, L-arabinitol and xylitol (5-12) as monomers for the preparation of a series of linear [/M, ]-type polyurethanes 97 and 98 by polycondensation in solution with... 

Low molecular mass linear and branched polyester resins are produced in a one-stage process at 125-240 C. The volatile condensation products are removed in vacuo (melt condensation process) or by passing a stream of inert gas through the resin melt (gas stream condensation process). Polycondensation in solution with azeotropic removal of water by solvent distillation (azeotropic process) is of lesser importance. High molecular mass copolyesters are produced in two stages as is used for poly(ethylene terephthalate). A precondensate is first obtained by transesterification of dimethyl terephthalate with an excess of diols. In the second stage, the molecular mass of the precondensate is adjusted to the desired value by polycondensation in special reactors with the maximum possible elimination of water and excess diols in vacuo at ca. 250 C. 

Various organic solvents were used as reactionary medium at nonequilibrium polycondensation in solution realization [96]. The solvent type influence on the synthesis reaction main characteristics (conversion degree Q and molecular weight MM) is well known and is explained usually by solvent various characteristics (dielectric constant, solubility parameter, heat of dissolution and so on) [96]. However, up to now the indicated effects general theoretical explanation is not obtained. Besides, at the solvent type influence analysis its correlation with polycondensation process quantitative characteristics (the same Q and MM) is usually considered, but any changes of polymer structure or reaction mechanism are not assumed, although the possibility of side reactions is noted repeatedly [96]. The authors [71, 127] studied the solvent influence on the enumerated above characteristics on die example of the rules of chloranhydride of terephthalic acid and phenolfthaleine low-temperature polycondensation (polyarylate F-2), performed in 8 different solvents [128]. 

Relationships, similar to the Eq. (29), do not take into account polycondensation in solution main element stmcture — macromolecular coil, although steric and conformational factors influence on polycondensation course is often mentioned. Therefore the authors [46] performed the study, how macromolecular coil stmcture could influence on the value Eo and, hence, on polycondensation reaction kinetics. 

Hence, the stated above results assume, that polycondensation in solution products (macromolecular coils) stracture defines polymers in condensed state stmcture and properties. The application of fractal analysis and cluster model ideas allows to both to point out these changes tendencies and to obtain polymers properties quantitative estimation [158]. 

Vinogradova, S. V Vasnev, V. A. Korshak, V. V. The some laws of low-temperature polycondensation in solution. High-Molecular Compounds, B, 1967,9(7), 522-525. 

The ridge-like polyarylesteiketones have been synthesized by means of one-stage polycondensation in solution of bis(4-nitrophenyl)ketone with phenolphthalein, o-cresolphthaleine, 2,5,2 -5 -tetramethylphenol-phthaleine and timolphthaleine [352]. Authors have shown that the free volume within the macromolecule depends on position, type and number of alkyl substitutes. 

The block copolymers, containing units of polyarylesterketones and segments of thermotropic liquid-crystal polyesters of different length, are synthesized by means of high-temperature polycondensation in solution... 

Example 4.12 Synthesis of a Lyotropic Liquid Crystalline Aromatic Polyamide from Terepbtbalic Acid Dicbloride and Silylated 2-chloro-1,4-Phenylenediamine by Polycondensation in Solution... 

Solution polycondensation is used in industry to produce polyurethanes, polycarbonates and certain types of polyamides and polyesters. Polycondensation in solution is most frequently used when it is difficult or impossible to keep the reactants in the same phase using bulk polymerization, or when the melting point of the resulting polymer is too high. Solution polycondensation takes place at lower temperatures than melt polymerization and enables efficient heat transfer to be maintained due to lower viscosity. However, solution polycondensation requires polymer separation from solution, recovery of solvent, and polymer washing and drying. 

Cholesteric polyesters were prepared from silylated derivatives of 2,3-di-(9-isopropylidene-D-threitol, DAS, or DAM with dicarboxylic acid dichlorides by polycondensation in solution [34]. Trifluoroacetic acid-water allowed an easy cleavage of the isopropylidene group without hydrolysis of the polyester. All these polyesters formed a broad cholesteric phase, and the polymers containing 5 or 10 mol per cent sugar diol displayed a blue Grandjean texture. 

The main temperature transitions in polycarbonates and polycarbonate -polytetramethylenoxide block copolymer resins, obtained by acceptor-catalytic polycondensation in solution, were studied by the method of differential scanning calorimetry. 

Figure 16 Synthesis of polyimide precursor 35 by the controlled polycondensation in solution of the bis- ortho-acid ester 33 and 4,4 -methylenebisbenzeneamine 34. The reaction initially gives short-chain amide-acid such as 35 that are transformed into polyimide 36 when the adhesive is processed at high temperature.

Figure 6.19 Synthesis of poly[oxy(2-chloro-l,4-phenylene terephthalate-co-1,4-cyclohexylenedimethylene terephthalate) by polycondensation in solution.

Fig. 19 Synthesis of poly(ethersulfone)s by A Friedel-Crafts sulfonylation and B by nucleophilic polycondensation in solution using phenolates and C melt polycondensation using trimethylsUyl derivatives of bisphenols... 

Polyarylethersulfones combine the flexibility of ethers and the strong cohesion of sulfone groups. They can be prepared using two methods. The first one utilizes polycondensation in solution between a sodium diphenoxide and a dichlorinated derivative, for example ... 

FIG. 3.14 Synthesis of poly(ether suIfone)s by (a) Friedel Crafts sulfonylation. (b) nucleophilic polycondensation in solution using phenolates. and (c) melt polycondensalion using trimethylsilyl derivatives of bisphenols. 

Figure 9.4 Size exclusion chromatographic analysis of the mixture of oligoimides 31 (Fig. 9.15) at various degrees of polycondensation in solution at 105 °C in benzyl alcohol.

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