Phthalic anhydrides, polycondensation

Maleic anhydride, 98 g (1.0 mol), 148 g (1.0 mol) of phthalic anhydride, and 160 g (2.1 mol) of 1,2-propanediol are poly condensed in a three-necked flask equipped with a mechanical stirrer, a nitrogen inlet, and a distillation head connected to a condenser and a receiver flask. The flask is placed in a salt bath preheated at 160°C. Water begins to distill and the temperature is then raised gradually to 190°C. The polycondensation is stopped (after about 15 h) when the reaction mixture has an acid number of 50 (see Section 2.3.8.4.1) (Scheme 2.54). A slightly different procedure is described in ref. 423. 

Reactions of the Methyl Groups. These reactions include oxidation, polycondensation, and ammoxidation. PX can be oxidized to both terephthalic acid and dimethyl terephthalate, which are then condensed with ethylene glycol to form polyesters. Oxidation of OX yields phthalic anhydride, which is used in the production of esters. These are used as plasticizers for synthetic polymers. MX is oxidized to isophthalic acid, which is also converted to esters and eventually used in plasticizers and resins (see Phthalic ACIDS and otherbenzenepolycarboxylic acids). 

Two different synthetic routes to polyesters are through the reaction of glycols or other polyfunctional hydroxy-compounds emd anhydrides such as phthalic anhydride, and by the reaction of acid chlorides with glycols or bisphenols. These two reactions may be regarded as irreversible. In the case of polyester-forming reactions that involve the use of acid chlorides (Section 5.7), the reaction proceeds better when the hydrochloric acid produced in the polycondensation is effectively removed, by neutralization, for example. 

Polyester-based resins are also used in bulk plastics in fiberglass reinforced fabrications such as boats, auto body repairs, and for very large structures such as industrial vessels and pipes, and ships for mine sweeping [10]. This technology uses a combination of polycondensation and vinyl-type (chain reaction) technologies to obtain the final composite product. The viscous, still fluid resin used for layup is a linear unsaturated polyester of relatively low-molecular weight. Unsaturation is introduced into the backbone of the polymer by using maleic anhydride to replace a part of the phthalic anhydride (e.g., Eq. 21.4). 

The first polyols used for rigid polyurethane (PU) foams were low molecular weight polyesters based on adipic acid, phthalic anhydride (PA) and various glycols or polyols. One example of a polyester of this type is the polycondensation product between adipic acid (AA), PA and trimethylolpropane (TMP) [1-3]. 

The development of highly crosslinked rigid polyisocyanurate foams opens an excellent area of applications for polyester polyols [4-8]. The required polyols do not need high functionality and the plasticising effect of polyester structures is extremely beneficial for these highly crosslinked systems [6]. The first polyester polyols used for these applications were low viscosity polycondensation products of AA with ethyleneglycol (EG) or diethyleneglycol modified with phthalic anhydride or triols. 

In order to improve the properties of these materials, Biswas and Mitra [120] synthesized carbazole-anhy-dride co-polycondensates by reacting for example carbazole (CBZ), phthalic anhydride (PhAn) and ZnCl2 at 265 5°C under nitrogen for 18 hours and other copolycondensates such as carbazole-tiimellitic anhydride (CBZ-TMA), carbazole-pyromellitic dianhydridc... 

Polycondensation of acid anhydrides (maleic and phthalic anhydrides) with diols (e.g. ethylene glycol) under microwave irradiation conditions has also been described for synthesis of unsaturated polyesters [52]. In addition to the previous procedure, the reaction temperature was increased to 200 °C and a Dean-Stark trap was used to remove water from the reaction mixture (Scheme 14.23). It was found that reaction times for the microwave and conventional procedures were comparable and depended on the rate of removal of water from the reaction system. 

Phthalic anhydride, maleic anhydride, fumaric acid, isophthalic acid, ethylene glycol, propylene glycol, diethylene glycol, styrene Bulk polycondensation followed by free-radical-initiated chain polymerization Construction, automotive applications, marine applications... 

According to this equation, the extent of the reaction (pA)cnt at the gel point depends only on the functionality / of the branch molecules, the molar fraction xk of the branch molecules, and the ratio ro of functional groups. These predictions are confirmed by experiment, since gel formation in the polycondensation of 2 mol of glycerine with 3 mol of phthalic anhydride (ro = 3 2/2 3) andxA = 1 always occurs at the same degree of reactionpA (Table 17-8). The gel point occurs at higher yields, however, than is calculated [theoretically (pA)cnt = 0.707]. Similar effects have also been observed with other multifunctional polycondensations (Table 17-9). 

Table 17-8. Experimentally Observed Critical Extents of Reaction for Gel Formation (pA)crit in the Polycondensation of 2 mol of Glycerol with 3 mol of Phthalic Anhydride...

Figure 17 8. Relationship between the observed yield (pA>exp and the calculated yield (pA)theor in the cross-linking polycondensation of isophthalic acid with trimethylol propane ( ) or pentaerythritol ( O) and phthalic anhydride with trimethylol propane (A ) or pentaerythritol (A) in toluene as a function of the dilution of the alcohol used (in kg mixture/mol alcohol). (From data of J. J. Bernardo and P. Bruins.)...

Initially, the monoglyceride of the oil is treated with appropriate amounts of saturated (phthalic anhydride) and unsaturated anhydride (maleic anhydride) at 150°C for 3-4 h to obtain the desired carboxyl or hydroxyl terminated pre-polymer. This then undergoes polycondensation with the necessary amount of bis(hydroxylmethyl) propionic acid to obtain the required hyperbranched polyester. High soUd coating systems may be... 

A few hyperbranched poly(ester amide)s have been prepared using a similar A2 + BBV approach, in which phthalic anhydride or maleic anhydride as an A2 monomer and diethanol amine as a BB 2 monomer were used. The polycondensation polymerisation technique is used to prepare the polymers. These poly(ester amide)s are modified by long alkyl chain (fatty acids) end groups. The dielectric properties of the modified polymers were investigated over a range of frequencies and temperatures. No relaxation peak was noticed in the dielectric spectrum at different temperatures. Castor oil and Mesua ferrea L. seed oil-based hyperbranched poly(ester amide)s are prepared using diethanol fatty amide of the oils with different types of anhydrides and dibasic acids with or without diethanolamine. 

In the case of isophthalic polyesters, the esterification is carried out in two stages. In the first stage, the slow reacting isophthalic acid is heated and polycondensated in the presence of excess glycols. This is followed by a second stage where the other acids/anhydrides (maleic anhydride and phthalic anhydride) are metered to the reactor. 

In this regard, the polycondensation of trimellitic anhydride chloride (4-chloro-carbonyl phthalic anhydride) with diamines at low temperature can be considered as a model reaction, and it has been the subject of numerous studies [190-192]. As usual, the first product formed in these reactions is poly(amide amic acid), which is eventually converted into poly(amide imide) by cyclodehydration. Some of these poly(amide imide)s from diamines and trimellitic anhydride have been reported as technical materials, and marketed as high Tg engineering thermoplastics [7]. 

A number of oligoimides (OI) with different molecular weights was synthesized by polycondensation of l,3-bis(3, 4,-dicarboxyphenoxy)benzene (R) and BAPS and by controlling the ratio of monomers to phthalic anhydride (PA) endcapper in accordance with the procedure described in [23]. Table 5.2 summarizes the properties and molecular weights of the R-BAPS-PA type OIs obtained from gel permeation chromatography. The lowest molecular... 

Method of synthesis - obtained by polycondensation of phthalic anhydride and propylene aloohol ... 

To improve the thermal stability of these polymers, Biswas and Mitra [349] prepared copolycondensates of carbazole (CBZ) with phthalic anhydride (PtiAn), trimellitic anhydride (TMA), pyromellitic dianhydride (PMDA), 1,4,5,8-naphthalene tetracar-boxylic dianhydride (NTDA), and benzophenone tetracarboxy dianhydride (BTDA) along with similar copolycondensates of PNVC. The thermal stabihty of copolycondensates was observed to depend on anhydride moiety in the order NDTA > BTDA > PMDA > TMA > PhAn for both the types of materials as given in Table IX. Table X shows the isotherm degradation stability of pairs of polycondensates, and the data confirm the high thermal stability of NTDA over the other materials. 

The preparation methods for the synthesis of unsaturated and saturated polyester resins were also elaborated for micro-wave conditions. In the polyaddition reactions of alkylene oxides (i.e., epichlorohydrin) and acid anhydrides (i.e., maleic and phthalic anhydrides), unsaturated polyesters were prepared in the presence of lithium chloride as a catalyst (Figure 30). In comparison with polycondensation reactions of acid anhydrides with diols, these reactions proceed without the release of by-products. 

The most common example of alkyd resin formation is from the polycondensation of glycerin, phthalic anhydride, and fatty acid. The reaction between trifimctional glycerin and difimctional anhydride could gel before the polycondensation was complete, but with the addition of a monocarboxylic fatty acid the formation of a somewhat linear polymer is possible. This polymer is soluble in aliphatic solvents if the eontent of fatty acid is sufficiently high. 

There is a wide variety of possible structures based on the use of glycerol (v = 3), trimethylolpropane (n = 3), pentaerythritol (n = 4), and sorbitol (n = 6) or their mixture as polyol, reacting not only with phthalic anhydride (w = 2) but also with pyromellitic dianhydride (w = 4), citric acid (v = 4), trimellitic acid (v = 3), or their mixture as polyacid. The most important resins are those obtained from the polycondensation of 0-phthalic anhydride with glycerol, and the resulting network is represented hereafter. 

The double bond in the maleic acid is inert toward polycondensation. Note that the degree of unsaturation (average number of double bonds per repeating unit) could be varied from zero to one by employing mixtures of a saturated diacid, e.g., phthalic anhydride (III) with the maleic to form copolyesters with saturated and unsaturated repeating units ... 

Wang et al. [135] prepared a novel ABB monomer (1-14, Scheme 8), namely 4-[4-(2,4-diaminophenoxy)phenoxy] phfhalic acid 2-methyl ester, which was polymerized to form the precursor polyamic acid monomethyl ester. The direct polycondensation of the ABB monomer was carried out to form polyamic acid monomethyl ester as a precursor and had a M of 12,000 Da. Chemical imidization in the presence of acetic anhydride and pyridine gave hb-PIs with low DB. The DB of the precursor, as determined by the H NMR spectra, was only 7%. They ascribed the low DB to the differences in the reactivities of the amino groups. End modification reactiOTis were accomplished with acetyl chloride, benzoyl chloride, and phthalic anhydride to form end-capped polyimides. The end-group-modified polyimides were soluble in polar aprotic solvents such as DMSO, DMF, and NMP. TGA measurements showed Ta,s% in the range of 400-520°C, and Tg of 200-258°C. The hb-PIs showed film-forming ability, but they were more brittle than analogous linear polymers. 

Unsaturated polyesters obtained by polycondensation of propylene glycol with maleic acid and ortho-phthalic anhydride (50 50) are photooxidized by molecular oxygen whereas they are completely non-reactive with singlet oxygen. The photolysis of unsaturated polyesters shows disappearance of double bonds and partial decom-... 

A third synthetic approach which came up in the years 1967-1970 was polycondensation of diisocyanates with tetracarboxylic anhydrides (Formula 6.4, top). Syntheses of phthalimides from phthalic anhydride and isocyanates were known since 1900 [50], but it took more than six decades until this reaction was adopted to the preparation of polyimides [51-55]. This approach is flexible, because it is... 

Apparently, the first polycondensation of a cyclic anhydride is described in a patent of 1916 which deals with the reaction of phthalic anhydride and glycerol. This reaction and other polycondensations of glycerol represent examples of a2 -I- ba polycondensations, which are discussed in Chap. 10. RO-PCs of phthalic anhydride with a,co-alkanediols were mentioned in papers and patents of Carothers, but a detailed description of individual examples was never provided. Homopolyesters of phthalic acid have never found any application, but phthalic anhydride plays a role as comonomer in unsaturated copolyesters based on maleic and/or fumaric acid. 

Tractable polymers can be prepared when amino and anhydride functions are not located on the same aromatic ring, and different strategies were employed to obtain soluble polymer. AB benzhydrol imide was prepared by polycondensation of 4-(3-amino-l-hydroxymethylene) phtlialic acid monomethyl ester in NMP. The polymer soluble in NMP has been used as adhesive and coating.56 A second approach was based on an ether imide structure. AB aminophenylether phthalic acids (Fig. 5.34) were prepared by a multistep synthesis from bisphenols.155 The products are stable as hydrochloride, and the polycondensation takes place by activation with triphenylphosphite. The polymers are soluble in an aprotic polar... 

---