Poly polycondensation reaction

The second step is the thermal conversion of borylaminoborazine into poly(borylaminoborazine). Continuous elimination of parent alkylamine is the main by-product dining the thermal polycondensation of 2,4,6-trialkylaminoborazine (see earlier). We expected the continuous elimination of the starting 5-alkylam i noborane during the thermal polycondensation of borylborazine. However, the alkylami noborane is a liquid, which requires that the thermal polycondensation must be performed in vacuo to continuously remove the evolving B(NHR)3 from the reaction mixture. This procedure also precludes any competing polycondensation reaction from B(NHR)3. 

Benzyl alcohol contaminated with 1.4% of hydrogen bromide and 1.1% of dissolved iron(II) polymerises exothermally above 100°C. Bases inhibit the polymerisation reaction. In a laboratory test, alcohol containing 1% of HBr and 0.04% of Fe polymerised at about 150° with an exotherm to 240° C. Formation and iron-catalysed poly-condensation of benzyl bromide seems to have been implicated. See Benzyl bromide Molecular sieve, or Catalytic impurities See Other BENZYL COMPOUNDS, POLYCONDENSATION REACTION INCIDENTS... 

Fatty acids have also been converted to difunctional monomers for polyanhydride synthesis by dimerizing the unsaturated erucic or oleic acid to form branched monomers. These monomers are collectively referred to as fatty acid dimers and the polymers are referred to as poly(fatty acid dimer) (PFAD). PFAD (erucic acid dimer) was synthesized by Domb and Maniar (1993) via melt polycondensation and was a liquid at room temperature. Desiring to increase the hydrophobicity of aliphatic polyanhydrides such as PSA without adding aromaticity to the monomers (and thereby increasing the melting point), Teomim and Domb (1999) and Krasko et al. (2002) have synthesized fatty acid terminated PSA. Octanoic, lauric, myristic, stearic, ricinoleic, oleic, linoleic, and lithocholic acid acetate anhydrides were added to the melt polycondensation reactions to obtain the desired terminations. As desired, a dramatic reduction in the erosion rate was obtained (Krasko et al., 2002 Teomim and Domb, 1999). 

They also synthesized polymeric iniferters containing the disulfide moiety in the main chain [149,150]. As shown in Eq. (30),polyphosphonamide,which was prepared by the polycondensation reaction of phenyl phosphoric dichloride with piperadine, was allowed to react with carbon disulfide in the presence of triethylamine, followed by oxidative coupling to yield the polymeric iniferter 32. These polymeric iniferters were used for the synthesis of block copolymers with St or MMA, with the composition and block lengths controlled by the ratio of the concentration of the polymeric iniferter to the monomer or by conversion. The block copolymers of polyphosphonamide with poly(St) or poly(MMA) were found to have improved flame resistance characteristics. 

Polycondensation reactions of 2 with diphenols were carried out in DMAc at 160°C using an excess of potassium carbonate to yield viscous solutions ofthe desired poly(aryl ether ketone)s. Judging by the viscosity increase, the polymerization reaction was near completion after only about 8h at 160°C. Aqueous... 

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. 

Galbis et al. described a variety of carbohydrate-based linear polyesters 61 of the poly(alkylene dicarboxylate) type that were obtained by polycondensation reactions of the alditols 2,3,4-tri-(9-methyl-L-arabinitol (9) and 2,3,4-tri-O-methyl-xylitol (10), and the aldaric acids 2,3,4-tri-(9-methyl-L-arabinaric acid (26) and 2,3,4-tri-(9-methyl-xylaric acid (27), butanediol, and adipic acid were also used as comonomers [28]. Copolyesters of the poly(aIkylene-c )-arylene dicarboxylate) type were obtained using bisphenols as comonomers (Scheme 1). Chemical polycondensation reactions were conducted in bulk or in solution. Enzymatic polycondensation reactions of adipic acid with the above-mentioned alditols were carried out successfully using Lipozyme and Novozyme 435. The hydrolytic degradations of some of these polyesters were also described. 

This type of reaction was a base for polycondensation reactions in the presence of preformed macromolecular compounds. It was found that high molecular weight poly(terephtalamides) are obtained by use of poly(4-vinylpyridine), P4VP, in the place of pyridine. The results are presented in the Table 6.1... 

When the ratio of template to acid is close to 0.5, the viscosity of the product is more than 3 times higher than the viscosity of the polymer obtained without the template. PEO participates in the change of local concentration by interaction with carbonyl groups, but not in the activation. Solution of LiCl in N-methylpyrrolidone with PlOCeHsls was found very effective system for synthesis of amides by the direct reaction of acids with amines in the presence of polymeric matrix. High molecular weight poly(aminoacids) obtained by direct polycondensation reaction, promoted by triphenyl phosphite and LiCl in the presence of poly(vinylpyrrolidone), were synthesized by Higashi et al The results for polymerization of L-leucine in the presence of poly(vinyl pyrrolidone) are presented in the Table 6.3. 

Table 6.4 Effect of the molecular weight of poly(vinyl pyrrolidone), PVP, on the polycondensation reaction of L-leucine. [Reprinted from N. Yamazaki and F. Higashi, Adv. Polym. Sci., 38,1 (1981)]...

For polycondensation reactions such as the final poly condensation of polyester, the reaction equilibrium and the reaction rate are mainly influenced by the removal of ethylene glycol (13) ... 

The mechanochemical polycondensation reaction has been studied using heterochain polymer systems—polyethylene terephthalate poly-(e-caprolactam), cellulose, etc.—characterized by end groups that can be activated to increase their own number by mechanochemical destruction of corresponding polymers. The mechanochemical destruction was done in the presence of some suitable condensing agents, such as aliphatic and aromatic diamines and fatty acid dichlorides. 

Plant cleaning incidents, 330 Platinum compounds, 330 Platinum group metals, 331 Poly(aminium) perchlorates, 331 Polyazacaged metal perchlorates, 332 Polycondensation reaction incidents, 332 Poly(dimercuryimmonium) compounds, 332 Poly(dimethylsilyl)chromate, 333 Polymeric peroxyacids, 333 Polymerisation incidents, 333 Polynitroalkyl compounds, 336 Polynitroaryl compounds, 337 Polynitroazopyridines, 340 Polyperoxides, 341 Polypropylene powder, 342 Precious metal derivatives, 342 Preparative hazards, 342... 

Free radical initiators or active hydrogen compounds such as amines or alcohols are not very effective initiators for the polymerization of lactones. Polyesters of low molecular weight are produced by these techniques. For example, copolymerization of various lactones in the presence of water at 200 °C proceeded via a hydrolysis followed by the polycondensation reaction of the hydroxy acid, giving low molecular weight products [67-69]. Low molecular weight (=10,000) tri-block copolymer (CL-b-EO-b-CL) has been prepared from e-CL and poly(ethylene glycol) (Mn=10 3) by carrying out the polymerization at 165 °C for several hours in the absence of catalysts [70]. 

The oxidative coupling of 2,6-disubstituted phenols to poly-(arylene oxides) is a polycondensation reaction, in which polymer molecules couple with other polymer molecules as well as with monomer. Unstable quinone ketals formed by coupling of a polymeric aryloxy radical at the para position of the phenolic ring of a second radical are believed to be intermediates or the reaction. The ketals may be converted to polymeric phenols either by a series of intramolecular rearrangements or by disproportionation to aryloxy radicals, leading to a mobile equilibrium between polymer molecules of varying degree of polymerization. Both processes have been shown to occur, with their relative importance determined by the reaction conditions. 

Various high molecular weight poly (ary limidazole) structures (xvii) have also been synthesized by Chauveau et al. [17]. The desired polymers were obtained by a one-pot polycondensation reaction involving a bis(a-diketone) (xv), an aromatic dialdehyde (xvi) and ammonium acetate under microwave condition. 

Polycondensation reactions were also carried out using a mixture of ethylene-diamine and adipic acid (55). IR techniques again were usai to confirm the polymer composition. The results are summarized on Table 9. The chemistry of poly(ethylene terephthalate) mechanical polycondensation with diamines proceeds as follows ... 

The first linear polymers containing [2]catenanes in their backbones (mechanically linked main chain polymers, architecture A) were based on the Sauvage transition metal-coordinated catenanes. Polycondensation reactions were carried out between a diacid and a catenane diol to give a poly[2]catenane with Mn (600000) and Mw (4200000) based on polystyrene standards (Figure 4). 

Under certain conditions, the equilibrium constant for the formation of poly(ethylene terephthalate) (PET) was shown [30] to be 9.6 that is, under the conditions employed the polycondensation reaction coefficient leading to the formation of PET was 9.6 times greater than the rate coefficient for glycolysis of PET. 

A side reaction often occurring in polycondensation reactions that take place in the molten state is the formation of cyclic oligomers. As already mentioned (Section 5.2), this is an important group of reactions in the preparation of poly(ethylene terephthalate). The reactions that lead to cyclooligomerization are, of course, not degradative the cyclic material is in equilibrium with linear polymer molecules. 

---