Melt polycondensation

The polymer is then dried thoroughly and stored for subsequent processing. Whenever a polyester is made by melt polycondensation, a small amount of cycHc oligomer is formed which is in equiHbrium with the polymer. This can be extracted with solvents from soHd polymer but when the... 

PBT is produced by the transesterification of dimethyl terephthalate with 1,4-butanediol by means of a catalyzed melt polycondensation (19). PBT is also semicrystalline and is an extremely tough resin. Several commercial resins use a blend of PBT with another resin, such as PET, polycarbonate, or nylon. Typically, composites of PBT contain 20—30 vol % fiber glass. 

PolybenZimidaZoles. The polyben2imida2oles (PBIs) are generally produced by the high temperature, melt polycondensation reaction of aromatic bis-ortho-diamines and aromatic dicarboxylates (acids, esters, or amides) in a reaction such as that shown in equation 11 to form ben2imida2ole [51-17-2] as the repeating unit. 

The material, Hostamid, LP700, is said to be a melt polycondensate of the diamines (I) and (II) above with terephthalic acid and up to 70% of e-caprolactam but has never been commercially marketed. 

Some of the typical conditions of polycondensations used for aliphatic and aromatic monomers are not suitable for furan derivatives, e.g., the melt polycondensation of 2,5-furan dicarboxylic acid chloride with 2,5-b/s(hydroxymethyl) furan at about 80 °C only yields a black insoluble product5. The hydrochloric acid liberated in the reaction is clearly responsible for the charring of the furanic diol which like its simpler homologue furfuryl alcohol, resinifies rapidly in acidic media (see below). 

Unsaturated polyesters are low-molar-mass polyesters obtained by melt polycondensation of 1,2-diols with saturated and unsaturated anhydrides or dibasic... 

Polyether-based thermoplastic copolyesters show a tendency toward oxidative degradation and hydrolysis at elevated temperature, which makes the use of stabilizer necessary. The problem could be overcome by incorporation of polyolehnic soft segments in PBT-based copolyesters [31,32]. Schmalz et al. [33] have proposed recently a more useful technique to incorporate nonpolar segments in PBT-based copolyesters. This involves a conventional two-step melt polycondensation of hydroxyl-terminated PEO-PEB-PEO (synthesized by chain extension of hydroxyl-terminated hydrogenated polybutadienes with ethylene oxide) and PBT-based copolyesters. 

We examined several approaches for synthesizing polyanhydrides, including melt polycondensation, dehydrochlorination, and dehydrative coupling. Extensive details of these new polymer synthesis techniques and numerous polymerization conditions for a wide variety of polyanhydrides were previously described (1). 

Leong, K. W., Simonte, V., and Danger, R., Synthesis of polyanhydrides Melt-polycondensation, dehydrochlorination, and dehydrative coupling. Macromolecules, 20. 705-712, 1987. 

Synthesis of polyanhydrides from the aromatic dicarboxylic acids (isophthalic and terephthalic acids) by melt polycondensation was first... 

Scheme 2. Polyanhydride synthesis via melt polycondensation involves first the formation of oligomeric acetylated prepolymers, followed by condensation under vacuum. Acetic acid is formed as a byproduct of the second reaction.

In an attempt to avoid the polymerization/depolymerization equilibrium that occurs during melt polycondensation, Albertsson and Lundmark (1988) also studied the irreversible reaction of adipic anhydride with ketene. However, they reported very little difference in molecular weights when two ketene syntheses were compared to melt polycondensation and ringopening polymerization using a zinc catalyst (Albertsson and Lundmark, 1988). 

Polyanhydrides based on unsaturated and fatty acid-derived monomers are shown in Table III. Poly(fumaric acid) (PFA) was fist synthesized by Domb et al. (1991) by both melt polycondensation and solution polymerization. The copolymer of fumaric acid and sebacic acid (P(FA-SA)) has been synthesized and characterized (Domb et al., 1991 Mathiowitz et al., 1990b). The mucoadhesive properties of this polymer... 

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). 

Xu et al. (2001) synthesized the copolymers of a dimer fatty acid (dimer of oleic and linoleic acids) and sebacic acid (P(DA-SA)) by melt polycondensation of acetylated prepolymers. Degradation and drug release kinetics showed that increasing dimer acid content decreased the release rate (Xu et al., 2001). 

Poly(lactic acid) (PLA) has also been added to poly(SA) via melt polycondensation to produce the triblock copolymers poly(lactic acid-Wock-sebacic acid-Wock-lactic acid) (P(LA-block-SA-block-LA)) by Slivniak and Domb (2002). The PLA (d-, l-, and dl-) was incorporated by acetylation and addition to the PSA synthesis. They showed the formation of stable stereocomplexed particles with increased melting points and reduced solubility, and studied the degradation and drug release characteristics of the same (Slivniak and Domb, 2002). The stereocomplexes self-assemble as a consequence of the chirality in the PLA portions of the chains (Slivniak and Domb, 2002). 

Erdmann and Uhrich (2000 Erdmann et al., 2000) recently synthesized novel poly(anhydride-co-ester)s containing salicylic acid in the backbone, by melt polycondensation of the disalicylic acid ester of sebacic acid, poly[bis(o-carboxyphenoxy)sebacate] (PCPS) and the copolymer P(CPH-CPS). The release of salicylic acid (the active form of aspirin) from the former was studied in vitro and from the latter was studied in vivo (Erdmann and Uhrich, 2000 Erdmann et al., 2000). Similar polymers that release 5-amino salicylic acid, and p-nitro salicylic acid have been prepared... 

Several routes have been reported for the synthesis of aromatic poly(azole)s such as poly(benzimidazole), poly(benzoaxazole), and poly(benzthiazole) melt polycondensation of dicarboxylic acid diphenyl esters with tetramines21 and high-temperature solution polycondensation of dicarboxylic acids or their derivatives with tetramine hydrochlorides in PPA.22 PPA acts as condensing agent and solvent. Ueda etal.23 developed a modified method for the synthesis ofpolyazoles with the use of PPM A. 

Novel poly(aryloxydiphenylsilane) is prepared from Bisphenol AF (2,2-bis(4-hydroxyphenyl)-l, 1,1,3,3,3-hexafluoropropane) (1) and dianilinodiphenylsi-lane (30) by melt polycondensation at elevated temperatures under reduced pressure of 1 to 2 Torr (Scheme 18).27 The molecular weight of the poly-(aryloxydiphenylsilane) derived from anilinosilane and bisphenols have been reported to be highly dependent on the reaction temperature in the melt polycondensation.28... 

Polyamides can be obtained by the melt polycondensation between dicarboxylic acids and diamines. They have the general structure as follows ... 

Many studies on the modelling of esterification, melt polycondensation, or solid-state polycondensation refer to the reaction scheme and kinetic data published by Ravindranath and co-workers. Therefore, we will examine the data sources they have used over the years. The first paper concerned with reactor modelling of PET production was published by Ravindranath el al. in 1981 [88], The reaction scheme was taken from Ank and Mellichamps [89] and from Dijkman and Duvekot [90], The kinetics for DEG formation are based on data published by Hovenkamp and Munting [60], while the kinetics for esterification were deduced... 

Challa, G., The formation of polyethylene terephthalate by ester interchange II. The kinetics of reversible melt polycondensation, Macromol. Chem., 38, 123-137 (1960). 

Laubriet, C., LeCorre, B. and Choi, K. Y., Two-phase model for continuous final stage melt polycondensation of poly(ethylene terephthalate). 1. Steady-state analysis, Ind. Eng. Chem. Res., 30, 2-12 (1991). 

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