Search

Copolycondensation of isophthalic acid (IPA)/terephthalic acid (TPA) with various combinations of 2,2-bis(4-hydroxyphenyl)propane (BPA) and hydroquinones (HQs) or bisphenols (BPs) was conducted to study the effects of the compositions of IPA/TPA and of BPA/HQs or BPA/BPs upon the reaction. Different from homopolycon-densation of each of diol components examined where most of the reaction was facilitated by lower contents of IPA at about 70 mol %, the copolycondensation was influenced by a combination of diol components. With chlorohydroquinone (ClHQ) or bis(4-hydroxyphenyl)sulfone (BPS) having a polar chlorine or sulfonyl substituent, the reaction proceeded most satisfactorily at IPA/TPA = 30/70, whereas it was IPA/TPA = 50/50 for the reaction with nonpolar methyl substituted methylhydroquinone (MeHQ). The reaction with 2,2-bis(3,5-dichloro-4-hydroxyphenyl)propane (TC-BPA), despite having polar chlorine substituents in TC-BPA, was not affected by IPA/TPA compositions. Alternatively, from the viewpoint of the compositions of diol components, the reactions containing 30-50 mol % of HQs or BPS yielded better results except for the reaction of IPA/TPA = 70/30, in which higher contents of MeHQ was more favorable. On the basis of sequence distributions of diol components in the resultant copolymers determined by NMR, compositions of IPA/TPA or diol components and combinations of the diols producing random copolymers yielded better results in copolycondensation.

Polyamidation with phenyl dichlorophosphite (PDCP) as a new condensing agent was studied. A model reaction of benzoic acid and aniline with PDCP through a change in their addition order revealed that PDCP reacted with aniline more favorably than it did with the acid, and it could activate about 2 mol of aniline to produce benzanilide in a nearly quantitative yield. A preferential reaction with aniline occurred even in the presence of the acid. The reaction was applied to the polyamidation of dicarboxylic acids and diamines or of p-aminobenzoic acid (PABA) with 0.6 equiv of PDCP with respect to the amino groups in pyridine/N-methyl-2-pyrrolidone in the presence of LiCl. Polyterephthalamides and polyisophthalamides with moderate inherent viscosity values were produced. The polycondensation of PABA was significantly promoted by the slow addition of PDCP over a period of 20–40 min and the presence of LiCl, producing poly(p-benzamide) with inherent viscosity values of about 2.4. Unsubstituted PDCP and PDCPs with an electron-donating methoxy substituent afforded better results. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4126–4131, 2004

The solution polyesterification of dicarboxylic acids in pyridine, the activated intermediates of which were difficult to dissolve in tosyl chloride/dimethylformamide/pyridine, was investigated in the presence of lithium chloride. The solubility of the activated dicarboxylic acids was largely improved by the presence of the salt, and the polycondensation with bisphenols was greatly facilitated. The salt was more effectively added to a pyridine solution of dicarboxylic acids than to the activated dicarboxylic acids in pyridine. The favorable additive effect on the improved solubility was attributed to a lowered degree of association of the activated dicarboxylic acids, which led to distributions of the resulting oligomers from bisphenols at an earlier stage closer to the theoretical ones and yielded better polycondensation results. The reaction, which proceeded through favorable distributions of the co-oligomers, produced copolymers of higher inherent viscosities and slightly block sequence distributions determined by NMR.

The polycondensation of isophthalic acid (IPA)/terephthalic acid (TPA) with aromatic diols by tosyl chloride/dimethylformamide/pyridine in solution was examined through changes in the IPA/TPA compositions, the kinds of dihydroxyl components, the periods of their addition, and the reaction temperatures. The reaction proceeded favorably at IPA/TPA ratios of 70/30 to 50/50, similarly to an earlier report on the interfacial reaction. The effects of the compositions were significant in the reactions with monosubstituted hydroquinones. The results were examined from distributions of the resulting oligomers prepared at a reaction extent of 0.7, determined by gel permeation chromatography. The reaction producing better results exhibited distributions closer to the theoretical ones. The period of addition also favorably affected the distributions as well as the results of the polycondensation. These results were attributed to the change in the reaction method, in which the diols reacted with the aggregates that formed from the activated IPA and TPA. The change was likely caused by the degree of association of IPA and TPA in the aggregates, on the basis of melting points and IR spectra of mixtures of dimethyl esters of IPA and TPA prepared by the quenching of the aggregates with methanol.

A two-stage copolycondensation of a mixture of equal parts of isophthalic acid and terephthalic acid was conducted using a tosyl chloride/dimethylformamide/pyridine condensing agent. In the initial stage x,y-dihydroxytoluenes (x,y-DHTs) or 2,4-dihydroxyethylbenzene (2,4-DHEB) was used and in the next stage isomeric DHTs or the DHEB was used. The results were examined in terms of how the reaction of the resulting oligomers with the next monomers proceeded, which was evaluated from distributions of the next monomers in the resultant copolymers as determined by 1H NMR. A structurally selective reaction was observed. The preformed oligomers from symmetrically substituted 3,5-DHT reacted randomly with similarly substituted 2,6-DHT or asymmetric 2,4-DHEB, but those from 2,4-DHEB reacted selectively with both of 3,5- and 2,6-DHT. In the reactions of the oligomers from 2,6-DHT, they reacted randomly with 2,6-DHT but selectively with 2,4-DHEB. Such selective reactions were also observed in the reaction of p-isomeric 2,5-DHT with the oligomers prepared from 3,5- or 2,6-DHT. When the monomers were copolymerized simultaneously instead of stepwise, they distributed randomly in the resultant copolymers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5687–5694, 2004

The random copolycondensation of isophthalic acid/terephthalic acid with various combinations of bisphenols (M1 and M2) with a tosyl chloride/dimethylformamide/pyridine condensing agent was carried out to investigate the effects of the monomer reactivity ratios, r1′ and r2′, on the reaction, like r1 and r2 in radical copolymerization. The ratios were calculated from the probabilities of finding an M2 unit next to an M1 unit and of finding an M1 unit next to an M2 unit, which were determined by an NMR analysis of the resultant copolymers. They were discussed with respect to the inherent viscosities (molecular weights) of the resultant copolymers. There was a fairly good relationship between r1′ and r2′ and the inherent viscosity values of the copolymers, indicating that copolycondensation could be facilitated by a combination of bisphenols; the lowering of r1′ and r2′ was indicative of random distributions in the copolymers. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3908–3915, 2003

In copolycondensation with 2,2-bis(4-hydroxyphenyl)propane (BPP) and bisphenols (BPs) containing various alkylidene linkages, the associative interactions between BP moieties in the resulting oligomers most likely affected the reaction. To modify the interactions to favorably control the reaction, several additives were examined in a two-stage polycondensation of an equimolar mixture of isophthalic acid and terephthalic acid, first with BPP (50 mol %) and next with additional BPP. Of additives used, diphenylmethane of an equivalent to BPP in the preformed oligomers was most effective. The results are discussed in terms of the distributions of resulting oligomers prepared at 70% extent of reaction. Better results were obtained when the distributions showed profiles similar to the theoretical one calculated on the basis that the reactivity of the oligomers is the same independent of their chain lengths. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 970–975, 2003

The copolycondensations of a mixture of equal parts of isophthalic acid and terephthalic acid with tetrachlorobisphenol A (TC-BPA) and various aromatic diol comonomers were performed with a tosyl chloride/dimethylformamide/pyridine condensing agent. The reaction with bisphenols containing nonpolar substituents yielded better results than the reaction with polar groups did. Dihydroxybenzenes smaller in size than bisphenols of two benzene rings, especially chlorohydroquinone and chlororesorcinol, were satisfactorily incorporated and yielded copolymers of high inherent viscosities and weight-average molecular weights (by gel permeation chromatography). The results of the copolycondensations were examined with sequence distributions in the resultant copolymers by NMR and were well evaluated by the ratio of the length of comonomer unit segments to TC-BPA unit segments. Homopolycondensation with TC-BPA in the presence of dichlorobenzenes as additives was also promoted to some extent.

A two-stage copolycondensation of a mixture of equal parts of isophthalic acid and terephthalic acid first with a′,b′-dihydroxyacetophenone (a′,b′-DHAP) and then with isomeric c′,d′-DHAP was examined at 60 and 80 °C. A structurally selective reaction was observed. At 80 °C, the preformed oligomers from symmetrically substituted 2′,6′-DHAP reacted better with similarly substituted 2′,6′- or 3′,5′-DHAP to give the copolymers of significantly higher inherent viscosity values than from the reaction with asymmetrically substituted 2′,4′-DHAP, whereas at 60 °C they did almost equally well with any c′,d′-DHAP. Similarly, the reaction of oligomers from 2′,4′-DHAP with asymmetrically substituted 2′,4′-DHAP or 2,4-dihydroxybenzophenone yielded better results than those from the reaction with 2′,6′- or 3′,5′-DHAP at both temperatures. The copolycondensations with comonomers of the structure independent of DHAPs were not affected by the preformed oligomers from DHAPs. The results are discussed in terms of the distributions of resulting oligomers determined by gel permeation chromatography. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 616–623, 2003

A two-stage co-oligomerization of the oligomers initially formed from an equimolar mixture of isophthalic acid (IPA) and terephthalic acid (TPA) and 2,2-bis(4-hydroxyphenyl)propane (BPA, 50 mol %) with bisphenols (BPs, 20 mol %) was carried out using a tosyl chloride/dimethylformamide/pyridine condensing agent. The distributions of the resulting oligomers (nx-mers), which were quenched with methanol, were determined by a combination of gel permeation chromatography (GPC) and NMR. These distributions (presented by molar percentage) were conveniently calculated with the equation nx (mol %) = nx (% mol by GPC) × n0 (mol % by NMR)/n0 (% mol by GPC), where nx (% mol) = nx (wt % by GPC)/its molecular weight. The results showed the distributions of the preformed IPA/TPA-BPA oligomers to be in fairly good accord with those obtained directly from GPC and to be supported by the NMR results. The calculation was applied to the co-oligomers prepared up to a reaction of 0.7, at which there was an increase in the number of higher oligomers indivisible by GPC and the distributions could no longer be determined by molar percentage. The calculated distributions are discussed in relation to the results of copolycondensation. The sequence distributions in the resulting co-oligomers, which were also examined by NMR, are compared with those in the copolymers. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 44–51, 2004

Two-stage copolycondensations of isophthalic acid/terephthalic acid (50/50) and a bisphenol (BP) first and then a comonomer BP were carried at 80 and 120 °C. BPs were divided into two groups: those with polar substituentsand those without polar substituents. The copolycondensation with any combination of BPs proceeded nearly equally well at 80 °C. However, the reaction at 120 °C was retarded differently by the groups of comonomers. For the preformed oligomers from BPs without polar substituents, the temperature did not affect the reaction very much, but the reaction was significantly retarded with BPs containing polar groups. All of the reactions of the oligomers from BPs having polar groups with comonomer BPs, regardless of their substituents, were greatly disturbed by the temperature rising. The results were attributed to the temperature effect on the way in which the oligomers reacted with comonomers due to the interactions between them, and they were examined in terms of the distributions of comonomers determined by 1 H NMR.

A two-stage copolycondensation of an equimolar mixture of isophthalic acid and terephthalic acid first with a bisphenol (BP) and then with another BP was carried out with a tosyl chloride/dimethylformamide/pyridine condensing agent. When the preformed oligomers from a BP with no substituent or a methyl substituent were allowed to react with another BP comonomer containing polar SO2, CO, or Cl groups, the copolycondensation was significantly promoted. Such effects were absent with the unsubstituted BP and the methyl derivative. In addition, during the reaction of oligomers from BPs with polar groups, a similarly polar BP did not react so effectively, and the unsubstituted BP did not have any effect on the copolycondensation. On the basis of the sequence distributions for the resultant copolymers determined by 1H NMR, it was likely that the copolycondensation could be promoted when the second comonomers were randomly distributed. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4024–4031, 2002

The solution polycondensation of a mixture of various parts of isophthalic acid (IPA) and terephthalic acid (TPA) with 4,4′-dihydroxydiphenylsulfone (BPS) with tosyl chloride/dimethylformamide/pyridine as a condensing agent was studied. To elucidate how the reaction should be done to obtain copolymers of high molecular weights, we examined the two-stage copolycondensation with BPS and 2,2-bis(4-hydroxyphenyl)propanes (BPAs) by changing the content of IPA/TPA and the amount of BPS or BPA used in the initial reaction. Controlling the reaction at an earlier stage could facilitate the copolycondensation. The polyesters of IPA/TPA and BPS of moderate inherent viscosity values up to 1.0 were obtained by the two-stage reaction with optimal amounts of BPS first and then additional BPS. Satisfactory results were also obtained by the dropwise addition of BPS over 10–20 min in the preparation of the IPA/TPA–BPS polymers containing less than 50 mol % TPA. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2607–2610, 2002

A two-stage solution copolycondensation of IPA/TPA (50/50), ineffective aliphatic p-xylyleneglycol (PXG), and effective bisphenols (BPs) using tosyl chloride/dimethylformamide/pyridine condensing agent was studied by examining factors, such as, kinds of BPs, reaction temperature, and the order of addition of PXG and BPs. Better results were obtained by initial reaction of PXG followed by BPs at a lower temperature (80 °C). BPs, when reacted randomly with the preformed oligomers from PXG, gave better results. These results were discussed in terms of the reaction of the preformed oligomers with PXG or BPs by measuring the distributions of growing oligomers by GPC and of PXG or BPs in the copolymers by 1 H NMR.

A thermotropic copoly(amide ester) exhibiting a nematic mesophase within the range of 240–360 °C was prepared by the solution copolycondensation of p-aminobenzoic acid (40–70 mol %) and m-hydroxybenzoic acid with diphenyl chlorophosphate in pyridine in the presence of LiCl. For control of the sequence distribution of p-aminobenzoic acid, the amount of LiCl and the dropwise addition of the phosphate were examined. The transition temperatures (from a solid phase to a nematic mesophase) of the resultant copolymers were affected by the period of addition and the amounts of the aminobenzoic acid and LiCl and were investigated in terms of the distributions of the monomers determined by 1H NMR. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1775–1780, 2002

A new condensing agent comprised of tosyl chloride (TsCl) and N-piperidinoformamide (NPF) in pyridine was very effective for the preparation of polyesters of aromatic dicarboxylic acids and aliphatic and aromatic diols with the highest molecular weight reported to date obtained by the solution reaction. The reaction yielded the most favorable results using about 0.3 equivalents of NPF with respect to the carboxyl groups and by dropwise addition of the diols over a period of about 20 min.

The polyesterification of a mixture of equal parts of isophthalic and terephthalic acids with 2,4-dihydroxybenzophenone (2,4-DHBP) and several dihydroxyacetophenones (DHAPs), from which polyesters of high molecular weight have not been prepared, was studied. Based on favorable results of two-stage copolycondensation with bisphenols first and then with 2,4-DHBP, factors such as dropwise addition of DHAPs, mol-% of them used in the initial stage, and the temperature in the subsequent stage were examined in a two-stage polycondensation, Favorable results were obtained by longer period of addition, initial reaction of 50-70 mol-%, and low temperature to 60 °C. The relationship between the temperature and the distribution of resulting oligomers determined by GPC was also examined. The copolymers obtained exhibited the glass transition temperatures and polymer melting points in the ranges of 165-183°C and of 280-310°C, respectively. Most of them were soluble in DMF, chloroform, cyclohexanone, and THF.

Aromatic dicarboxylic acids, such as terephthalic (TPA) and isophthalic (IPA) acids having different structures of the activated carboxyl groups were prepared in situ by the reaction of the diacids with TsCl/DMF/Py containing various amounts of DMF. The polycondensation involved by these carboxyl groups using 0.3 equivalents of DMF relative to dicarboxylic acids and by dropwise addition of bisphenols significantly improved the ηinh values of the IPA/TPA(50/50)-2,2-bis(4-hydroxyphenyl)propane (BPA) and IPA/TPA (50/50)-methylhydroquinone polymers. It was also the case for the polycondensations of BPA and various combinations of aromatic dicarboxylic acids other than IPA/TPA. It is likely that various structures of the aggregates between the activated IPA and TPA are involved in a mixture of them, and evaluated by melting points of mixtures of their dimethyl esters prepared by quenching the aggregates with methanol. Effect of the amounts of DMF and the dropwise addition of BPA upon the distribution of oligomers formed at an earlier stage was also examined.

A mixture of isophthalic acid (IPA) and terephthalic acid (TPA) was activated by a tosyl chloride/dimethylformamide/pyridine (Py) condensing agent in two steps via the treatment of a mixture of the initially activated IPA/TPA with additional TPA followed by the activation of TPA with the agent. The resulting mixture showed a solubility in Py different from that obtained by the activation of them all at once; the difference might be due to different structures of the aggregates of the activated IPA and TPA at the same composition of the diacids. The structures of the aggregates were evaluated on the basis of melting points and the IR spectra of a mixture of dimethyl esters of IPA and TPA produced by the quenching of the reaction mixtures with methanol. The mixture obtained by two-step activation showed lower melting points and spectral changes due to enhanced associations of the esters with respect to the mixture prepared by the activation of them all at once. The aggregates were also examined in terms of the distributions of IPA and TPA in thermotropic copolyesters prepared from methylhydroquinone and chlorohydroquinone by their transition temperatures and 13C NMR. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3884–3892, 2001

The reaction of sterically hindered hydroxyl groups at the 2-position of methylhydroquinone and phenylhydroquinone (PhHQ) to form esters was largely promoted by their slow addition to benzoic acid activated by diphenyl chlorophosphate in pyridine. A modification of this reaction was applied to the preparation of thermotropic terephthalic acid/PhHQ and 2,5-dichloroterephthalic acid/PhHQ polymers with randomly oriented phenyl substituents, and the properties of the polymers were studied in terms of their transition temperatures, which were determined by differential scanning calorimetry and microscopic observation. The melting points were lowered by about 30–50 °C by the dropwise addition of PhHQ over 10–30 min. The molecular structures of the 2,5-dichloroterephthalic acid/PhHQ polymers were studied by 13C NMR. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1726–1732, 2001

Copolycondensations of IPA, TPA, bisphenol A (BPA), and several cimonomers were carried out to improve thermal properties, such as, the glass transition temperature (Tg) of the IPA/TPA (50/50)–BPA polyester. Among the comonomers examined, 4,4′-Dihydroxydiphenylsulfone (BPS) and 4,4′-Dicarboxydiphenylsulfone (DCDPS) having a strongly dipolar sulfonyl group in the chain were significantly effective. The favorable effect upon the Tgs was studied by varying the amounts of BPS and DCDPS incorporated into the copolymers. In the copolycondensation with BPS, two-stage copolycondensation of BPA first and then BPS, the reverse order of reaction, and their spontaneous addition were examined to investigate the effect of distribution of the BPS unit segments in the copolymer upon the Tgs of the resulted copolymers. The distribution was briefly studied from distribution of the IPA/TPA-BPA oligomers in the initial reaction using GPC. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 875–879, 2000

A novel synthetic method for the preparation of copolyesters comprised of diols and bisphenols using tosyl chloride (TsCl)/DMF/pyridine (Py) as a condensing agent has been developed. A variety of combinations of monomers could produce relatively high molecular weight copolymers, and better results were obtained by initial oligomerization of diols followed by bisphenols. In order to demonstrate usefulness of this method, copolymers comprised of IPA/TPA (50/50), bis(2-hydroxyethyl)terephthalate (BHET),and several bisphenols were prepared and compared to the poly(ethylene terephthalate) (PET) modified by TPA and 2,2-bis(4-hydroxyphenyl)propane (BPA) diacetate in terms of their thermal properties. The length of mesogenic unit segments in the thermotropic IPA/TPA (50/50)-BHET/ 4,4'-dihydroxybenzophenone (4,4'-DHBP) (50/50) copolymer was changed by initial reaction of BHET followed by dropwise addition of 4,4'-DHBP in the two-stage polycondensation and also by varying the amounts of BHET used at the initial and final stages in the three-stage copolycondensation, and the results were studied by NMR and their thermal properties.

When a mixture of terephthalic acid (TPA) and various dicarboxylic acids was activated by tosyl chloride (TsCl)/dimethyl- formamide (DMF)/pyridine (Py), the resulting mixture became dissolved in Py, although the activated TPA was insoluble even at 120 °C. The temperature at which the mixture became soluble was varied with their compositions and the structure of diacids. Mixing the separately activated TPA and isophthalic acid (IPA) also improved the solubility of the activated TPA to some extent. The interesting phenomena were attributed to associations of the activated diacids through the dipole-dipole interactions between the carbonyl groups. The structures of associates were estimated in terms of transition temperatures of the thermotropic IPA/TPA-methylhydroquinone and IPA/TPA-chlorohydroquinone copolymers. The transition temperatures were significantly affected by the temperature of polycondensation, the preparative procedures of a mixture of the activated diacids, and several additives.

When mixtures of terephthalic acid (TPA) and 1,6-naphthalenedicarboxylic acid (NDC) or 4,4'-dicarboxydiphenylether (DCDPE), TPA, and isophthalic acid (IPA) were reacted in pyridine (Py) with Tosyl chloride (TsCl)/DMF/Py to activate the diacids, the reaction mixture was soluble in Py, despite each of the separately activated diacids being insoluble. The solubility of the activated diacids was examined at a variety of acid compositions and temperatures. It was expected that a competitive reaction among the diacids with an aromatic diol in solution might be different from those in the melt, resulting in a different distribution of the acids in the copolymers. The TPA/NDC-phenylhydroquinone and DCDPE/TPA/IPA-chlorohydroquinone copolymers were prepared in solution using TsCl/DMF/Py as the condensing agent and the transition temperatures of these liquid crystalline copolyesters were compared to those obtained by melt copolycondensation. A practical depression of the transition temperature by the solution polycondensation was observed.

Dihydroxybenzophenones and 4,4'-dihydroxydiphenylsulfone, which yield high-molecular-weight polyesters only difficultly by conventional methods, gave high-molecular-weight copolyesters through a two-stage copolycondensation involving initial induction of oligomerization with selected monomers followed by copolycondensation. The copolycondensation was studied by examining such factors as the kinds of initial monomers, their amounts, initial reaction times, and the order of reaction, and the results are explained in terms of oligomer distribution in the initial oligomerization as determined by GPC. Copolycondensation was also facilitated by lowering the temperature at the second stage of reaction.

Copolycondensations of IPA, TPA, BPA, and PHB were studied to investigate how PHB, which can form mesogenic segments, should be incorporated into the amorphous IPA/TPA–BPA polyester to obtain the thermotropic copolyester, unlike other copolymerizations studied so far by randomly introducing nonmesogenic components into the liquid crystalline polyesters. Random and controlled copolycondensations were attempted to regulate the segment length of mesogenic PHB units by stepwise addition of BPA and PHB through the two- and three-stage reactions using TsCl/DMF/Py as a condensing agent. Thermotropic copolyesters with ca. 40 mol % PHB could be obtained by a three-stage reaction, despite that more than 70 mol % PHB is needed to prepare by usual random copolymerization with PHB. The segment length of the PHB unit was indirectly studied from IPA/TPA–BPA oligomer distribution at initial reaction by means of GPC and from the NMR analysis of the resulting copolymers. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2371–2377, 1999

Copolycondensations of TPA, PhHQ, and several aromatic diacid and diol modifiers were examined for which kind of the modifiers incorporated is more effective to reduce the transition temperatures of the resulting copolyesters and how they affect the temperatures. The acid modifiers are more effective than the diol ones, significantly when they have substituents. As another type of modifier, HBA forming the ester bond of an AB structure different from the AABB structure of TPA/PhHQ polyester was also effective, and the lowering effect on the temperatures was varied by the mode of copolycondensations, being most remarkable when HBA was randomly introduced. The results obtained were discussed in terms of the disturbance and thereby weakening of the interchain dipole–dipole interaction between the carbonyl groups in the ester linkages due to the introduction of the diacid modifiers and of HBA having an ester bond of a different directionality. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 621–626, 1999

Copolycondensations of triethyleneglycol bis(4-carboxyphenyl) ether (PEG 3 ), p-aminobenzoic acid (PABA), and p-phenylenediamine (PPD) were studied in order to examine the effect of monomer sequences in the copolyamides upon the transition temperatures of the resulting copolymers. Random copolymerization of these monomers resulted in the copolymers exhibiting a nematic mesophase in a wide range of PABA content. On the other hand, the sequential copolymers composed of PABA/PPD=1/1 and 2/1, which were prepared from 4,4'-diaminobenzanilide (DABA) and N,N'-bis(4-aminobenzoyl)-p-phenylenediamine (BAB-PPD), respectively, did not show a mesophase

It is proposed that depression of the transition temperatures, especially the melting point (Tm), can be achieved by the introduction of a different amide bond structure into the copolyamides of dicarboxylic acids and diamines by copolymerization of aminocarboxylic acids, such as p-aminobenzoic acid. The effect was examined by the amount and distribution of the structure in the copolylamindes. Copolycondensations of PEG3, p-aminobenzoic acid, and diamines with different chain lengths showed that the structural change of the amide bond in the copolymers, especially its distribution, was more important than its total amount in them. Several types of aminocarboxylic acids were briefly examined to study the effect. © 1994 John Wiley & Sons, Inc.

Thermotropic copolyamides were prepared from triethyleneglycol bis(4-carboxy-phenyl)ether (PEG3) and two types of diamines, substituted p-phenylenediamines and 4,4'-diaminodiphenyls, and depression of melting point and isotropization temperature of the copolymers produced were measured as a function of diamine combination. The depression was not practically observed by the combinations of homologous diamines with several kinds and numbers of substituents, but significant by those of the diamines with different lengths of the mesogenic segments, and by the molar ratios of the diamines employed. The effect was discussed in terms of deviation of interchain hydrogen bonding between amide bonds in the main chain. © 1994 John Wiley & Sons, Inc.

Copolymerizations of polyethyleneglycol bis(4-carboxyphenyl)ethers (PEGn) with different n values were found to significantly lower the anisotropic transition temperature (Tm) of the copolymers produced, and the thermotropic copolyamides of thermally more stable nematic phases were obtained. The effect was investigated in terms of PEGm/PEGn molar ratios, the number of oxyethylene units, and the even—odd character of the flexible segment. Several modes of copolymerization were carried out to investigate the effect of monomer (PEGn sequence on Tm. By these copolymerizations thermally stable copolyamides even from p-phenylenic diamines such as methyl-p-phenylenediamine and p-phenylenediamine were obtained. © 1993 John Wiley & Sons, Inc.

New thermotropic liquid crystalline polyamides were prepared from polyethyleneglycol bis(4-carboxyphenyl)ether (PEGn, n = 2, 3, 4) and aromatic diamines by using triphenyl phosphite in pyridine as the condensing agent. Substituted p-phenylenediamines and 4,4′-diaminobiphenyls were successfully used; melting points and isotropization temperatures of the polyamides were changed by the kind and number of the substituents. Copolymerization of long chain aliphatic dicarboxylic acids was carried out at the lower melting point of the copolymer. Kink monomers were also incorporated into the polymer backbone. © 1993 John Wiley & Sons, Inc.

Significantly high molecular weight poly(isophthalic dihydrazide) of inherent viscosity up to 1.6 (DMSO) was prepared by the reaction of isophthalic acid and hydrazine monohydrochloride using phenylphosphonic dichloride in the presence of phosphorus compounds such as phosphine oxides. The phosphorus compounds used as additives were assumed to be involved in the reaction through a complexation with the monohydrochloride, enhancing the reactivity of the hydrazine. It was attempted to prepare copoly(hydrazide-amides) with different monomer sequences by changing the relative reactivity between diamines and the hydrazine using the phosphorus compounds. The copoly(hydrazide-amide)s were studied in terms of the dehydration reaction of hydrazide groups into 1,3,4-oxadiazole groups. © 1993 John Wiley & Sons, Inc.

The reaction of the N-phosphonium salt of pyridine derived from phosphorus oxychloride in pyridine was successfully used for the preparation of aromatic polyesters with high molecular weight when carried out in the presence of lithium chloride. In the copolycondensations of isophthalic and terephthalic acid with diphenols, the mode of reaction with the diacids was expected to produce several types of the diacid activated intermediates, which might control the sequences of the diacids in the copolymers. The possible variation of the sequences was studied in terms of the mode and copolymer properties such as glass transition temperatures and liquid crystalline transition temperatures. Competitive model reactions were carried out to discuss these relationships. © 1993 John Wiley & Sons, Inc.

A new condensing agent comprised of tosyl chloride (TsCl) and triphenylphosphine oxide (TPPO) in pyridine was very effective for the preparation of polyesters of aromatic dicarboxylic acids and bisphenols with higher molecular weight than those obtained from TsCl/dimethylformamide in pyridine. Among the phosphorus compounds examined TPPO was most effective, and the reaction using half an equivalent with respect to the carboxyl groups yielded the most favorable results at temperatures of more than 100°C.

High-viscosity polyesters can be prepared by the polycondensation of secondary aliphatic trans-cyclohexanedicarboxylic acid (t-CHDC) and hydroquinones using SOCl 2 /pyridine condensing agent at 80°C. Incorporation of its cis-isomer significantly affected η inh and the thermal property of the resulting copolymers. The copolymers of t-CHDC, hydroquinones, and p-hydroxybenzoic acid having different monomer sequences were prepared by changing the order of introduction of monomers.

High-energy phosphonium compounds were prepared by the oxidation of phosphorous acids and its esters with mercuric salts or halogens in pyridines, by a hydrolysis-dehydration reaction of diphenyl and triaryl phosphites or phosphonites with pyridines and also with metal salts, or by the reaction of phosphorus halides with tertiary amines. These salts are very reactive to nucleophiles, activating carboxyl, amino, or hydroxyl compounds via the corresponding phosphonium salts to yield carboxylic amides and esters in high yields on further aminolysis, alcoholysis, and acidolysis. These reactions, especially the hydrolysis-dehydration reactions with phosphites, were successfully extended to the direct polycondensation reaction of dicarboxylic acids with diamines, of free α-amino acids or dipeptides, and of carbon dioxide with diamines under mild conditions, yielding linear polymers of high molecular weight (polyamides, polypeptides, polyureas). Surprisingly high molecular weight was given by the reaction in the presence of polymer matrixes. The direct polyesterification of hydroxybenzoic acids and between dicarboxylic acids and bisphenols was achieved by the phosphonium salts derived from phosphorus halides such as hexachlorocyclotriphosphatriazene.

When activated with TsCl/dimethylformamide/pyridine in the presence of lithium, ammonium, or phosphonium salts, activated terephthalic acid of difficult solubility in pyridine became soluble. Depending on the kind and amount of the salt, terephthalic acid reacted smoothly with 3,3′-dimethyl bisphenol A to yield the corresponding polymer having high molecular weight. However, this reaction could not be successfully applied to the preparation of polyesters from other dicarboxylic acids of difficult solubility.

Moderate-molecular-weight copolyamides soluble in N-methylpyrrolidone (NMP) containing dissolved CaCl 2 can be obtained by polycondensation of terephthalic acid (TPA), p-phenylenediamine (PPD), and p-aminobenzoic acid (PABA) with triphenyl phosphite/pyridine in NMP. The randomly copolymerized polymers contain more than 40 mol-% of PABA and are easily soluble in NMP.

High-energy phosphonium compounds, the N-phosphonium salts of pyridines, were prepared by the oxidation of phosphorous acid and its esters with mercuric salts or halogens in pyridines, or by a hydrolysis-dehydration reaction of diphenyl and triaryl phosphites or phosphonites. These salts are very reactive to nucleophiles, activating carboxyl, amino, or hydroxyl compounds via the corresponding N-phosphonium salts to yield carboxylic amides and esters in high yields on further aminolysis, alcoholysis, and acidolysis. These reactions, especially the hydrolysis-dehydration reactions with phosphites, were successfully extended to the direct polycondensation reaction of dicarboxylic acids with diamines, of free α-amino acids or dipeptides, and of carbon dioxide and disulfide with diamines under mild conditions, yielding linear polymers of high molecular weight (polyamides, polypeptides, polyureas, and polythioureas).

The direct polycondensations of aromatic dicarboxylic acids, bisphenols, and diamines using diphenyl chlorophos. phate in the presence of phosphorus compounds were studied. Addition of the phosphorus compounds prevented effectively the gelation of the reaction mixture and produced soluble copolymers even if a high molar percentage of diamines was added. Based on the NMR study, it is considered that the reactivity of the phenolic groups of bisphenols increased due to the hydrogen-bond association with the phosphorus compounds resulting in change of the relative reactivity to diamines. This may lead to favorable monomer sequences in copolymers for the improvement of solubility and the prevention of gelation in the reaction mixture. The changes of monomer sequences caused by the phosphorus compounds were investigated also in terms of optical anisotropy of the copolymers prepared from isophthalic and tere-phthalic acids, methylhydroquinone, and diamines.

Polyterephthalamides of high molecular weight (ηinh up to 1.9) were obtained by the direct polycondensation reaction of terephthalic acid and aromatic diamines in the presence of poly(ethylene oxide) (PEO) with triphenyl phosphite in a N-methylpyrrolidone (NMP)–pyridine solution that contained lithium chloride. The molecular weights of the polymers produced varied with the amount and molecular weight of PEO, which showed maximum values when PEO with a molecular weight of 2.0 × 104−5.0 × 105 was used in a concentration of about 0.5 wt % in the solvent. The polycondensation reaction was significantly affected by the level of pyridine in a mixed solvent of NMP and pyridine and by the concentration of the lithium chloride added.

Direct polycondensation reaction of hydroxybenzoic acids with diphenyl chlorophosphate (DPCP) in pyridine was largely improved by carrying out the reaction in the presence of a formamide. Among the formamides examined, N,N-dimethylformamide (DMF), N,N-dimethylformamide, and N,N-dimethylacetamide were favorably used. A Vilsmeier adduct thus derived from DPCP and DMF was very effective especially for the preparation of high-molecularweight copolyesters from hydroxybenzoic acids. Copolymers of several combinations of hydroxybenzoic acids were prepared and their solubility and thermal properties were investigated. The polycondensations of aromatic dicarboxylic acids and bisphenols with the adduct were also studied.

La reaction promue par le chlorure de thioxyle et la pyridine peut activer selectivement les groupes carboxyles des acides hydroxybenzoiques pour donner des polyesters de viscosites intrinseques elevees jusqu'a 3,8

The direct polycondensation of terephthalic acid and p-phenylenediamine hydrochloride (PPD.2HCl) with thionyl chloride was found to be significantly promoted in N-methylpyrrolidone (NMP) by dissolved CaCl2 and tertiary amines. The inherent viscosity of the polymer obtained varied with the amount of CaCl2 and tertiary amines added. The reaction, when effectively promoted by CaCl2, proceeded homogeneously in the early state of polycondensation, and then resulted in a highly swollen gel. CaCl2 had to be present in the PPD.2HCl/tertiary amines/NMP solution as well as in the TPA/SOCl2/NMP mixture for the polycondensation to proceed to high molecular weight. Complexes of CaCl2, PPD.2HCl, and tertiary amines in NMP similar to the well known complex, CaCl2 · nNH3 (n = 2, 4, 8) was proposed to facilitate the polycondensation.