New polymer syntheses XCIII. Hyperbranched homo- and copolyesters derived from gallic acid and β-(4-hydroxyphenyl)-propionic acid

The hyperbranched homopolyester of gallic acid (GA) was prepared by polycondensation of acetylated gallic acid in bulk. Copolyesters of gallic acid and 3-hydroxybenzoic acid (3-HBA) or β-(4-hydroxyphenyl)propionic acid (HPPA) were prepared via the silylated monomers. The degree of branching was varied in both series via the molar fraction of gallic acid. A model reaction with silylated 4-methoxybenzoic acid suggests that all three acetoxy groups of gallic acid can react by ester interchange reactions under the chosen reaction conditions. Furthermore, highly branched copolyesters derived from equimolar ratios of HPPA and 2-, 3-, or 4-hydroxybenzoic acid, vanillic acid, or 4-hydroxycinnamic acid were synthesized. All these copolyesters were found to be amorphous with glass transition temperatures (T_g's) far below that of the hyperbranched poly(gallic acid). © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2347–2357, 1998     

Layer structures. VI. Chiral sanidic polyesters derived from 2,5-bis (dodecyloxy) terephthalic acids and 4,4′-dihydroxybiphenyl

Copolycondensations of (S,S)-2,5-bis(2-methylbutyloxy) terephthaloylchloride with 2,5-bis(dodecyloxy)terephthaloylchloride and with 4,4′-bistrimethylsiloxybiphenyl yielded a series of novel chiral thermotropic copolyesters. These polyesters were characterized by elemental analyses, inherent viscosities, ¹H-NMR spectroscopy, optical rotations, optical microscopy, DSC measurements, and WAXS powder patterns recorded with synchrotron radiation under variation of the temperature. All homo- and copolyesters formed a solid sanidic layer structure with melting temperatures (T_m) ≥ 200°C. A broad enantiotropic nematic or cholesteric phase is formed above T_m with isotropization temperatures (T_is) in the range of 275–325°C. Yet, the T_m of the chiral homopolyester is so high (378°C) that the melting process is immediately followed by rapid degradation. The cholesteric phases of the copolyesters displayed unusual mobile schlieren textures, but a stable Grandjean texture was never obtained. Cholesteric domains consisting of loose bundles of more or less helical main chains are discussed as supramolecular order responsible for the observed textures and their pronounced temperature dependence. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 947–957, 1997     

Liquid-crystalline polyimides, 16. Chiral thermotropic copoly(ester-imide)s based on isosorbide and N-(4-carboxyphenyl)trimellitimide

A series of chiral copoly(ester-imide)s was prepared by polycondensation of N-(4-carboxy-phenyl)trimellitimide with mixtures of isosorbide and phenylhydroquinone. All copolyesters are non-crystalline. They form a cholesteric melt, when containing more than 50 mol-% of phenyl-hydroquinone. Containing 5 or 10 mol-% of isosorbide a “Grand-Jean” texture is detected above 300°C and 350°C, respectively.     

Novel copolyesters containing naphthalene structure. I. From bis(hydroxyalkyl)naphthalate and bis[4-(2-hydroxyethoxy)aryl] compounds

Copolyesters containing naphthalene structure were synthesized from bis(hydroxyethyl)naphthalate (BHEN) or bis(hydroxybutyl)naphthalate (BHBN) and various aralkyloxy diols. The starting bis[4-(2-hydroxyethoxy)aryl] compounds were derived from a nucleophilic substitution of various bisphenols with ethylene carbonate in the presence of KI. Copolyesters having intrinsic viscosities of 0.45–0.60 dL/g were obtained by the melt polycondensation in the presence of metallic catalysts. The effect of reaction temperature and time on the formation of copolyesters were investigated to obtain an optimum condition for copolyesters manufacturing. Most copolyesters have better solubilities than polyethylene naphthalate (PEN) or polybutylene naphthalate (PBN) in aprotic solvents, such as N-methyl-2-pyrrolidone or m-cresol. The thermal properties of the copolyesters were investigated by the differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). Glass transition temperatures (T_g) of copolyesters result from BHEN were in the range of 90–141°C, and 10% weight loss in nitrogen were all above 460°C. Another series of copolyesters result from BHBN have T_g in the range of 75–135°C, and 10% weight loss in nitrogen of over 420°C. © 1996 John Wiley & Sons, Inc.     

Carbohydrate‐based copolyesters made from bicyclic acetalized galactaric acid

Mixtures of the dimethyl esters of adipic acid and 2,3:4,5‐di‐O‐methylene‐galactaric acid (Galx) were made to react in the melt with either 1,6‐hexanediol or 1,12‐dodecanediol to produce linear polycyclic copolyesters with aldarate unit contents varying from 10 up to 90 mole %. The copolyesters had weight–average molecular weights in the ～35,000–45,000 g mol^?1 range and a random microstructure, and were thermally stable up to nearly 300 °C. They displayed T_g in the ‐50 to ‐7 °C range with values largely increasing with the content in galactarate units. All the copolyesters were semicrystalline with T_m between 20 and 90 °C but only those made from 1,12‐dodecanediol were able to crystallize from the melt at a crystallization rate that decreased as the contents in the two comonomers approached each other. Copolyesters containing minor amounts of galactarate units adopted the crystal structure characteristic of aliphatic polyesters but a new crystal polymorph was formed when the cyclic sugar units became the majority. Stress–strain parameters were sensitively affected by composition of the copolyesters with the mechanical behavior changing from flexible/ductile to stiff/brittle with the replacement of adipate units by the galactarate units. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Effect of Polycondensation Reaction Conditions on the Properties of Thermotropic Liquid‐Crystalline Copolyester

In this study a range of wholly aromatic copolyesters based on kink m‐acetoxybenzoic acid (m‐ABA) monomer (33 mol%) and equimolar‐linear p‐acetoxybenzoic acid (p‐ABA), hydroquinone diacetate (HQDA) and terephthalic acid (TPA) monomers (67 mol%) have been synthesized by melt polycondensation reaction process at 280°C and 260°C for different time intervals. Characterization of copolyesters were performed by solution viscosity measurement, wide–angle X‐ray diffraction (WAXD), differential scanning calorimetry (DSC), hot‐stage polarized light microscopy, proton‐nuclear magnetic resonance analysis (¹H‐NMR). According to the results obtained, copolyesters showed thermotropic liquid crystalline behavior in an appropriate temperature range. The copolyesters were prepared in high yields. It was observed that the intrinsic viscosities of the copolyesters are increased regularly with increasing polymerization time and temperature. All the copolyesters were soluble in a trifluoroacetic acid/dichloromethane (30:70 v/v) except the copolyesters which were synthesized at 280°C in 5 h. According to the WAXD results; the degree of crystallinity of copolyesters were found to be between 5–15%. DSC and hot stage polarized light microscopy results showed that all the copolyesters are melt processable and a significant molecular interaction exist in a very broad temperature range (160°C and 165°C) in the nematic mesophase. The T_g values are increased with an increasing polycondensation reaction time and temperature and they were observed between 93–126°C. Fibers prepared by a hand‐spinning technique from the polymer melt exhibit well‐developed fibrillar structure parallel to the fiber axis.     

New polymer syntheses. CIX. Biodegradable,alternating copolyesters of terephthalic acid,aliphatic dicarboxylic acids,and alkane diols

Copolyesters with an alternating sequence of terephthalic acid and aliphatic dicarboxylic acids were prepared with three different methods. First, dicarboxylic acid dichlorides were reacted with bis(2‐hydroxyethyl)terephthalate (BHET) in refluxing 1,2‐dichlorobenzene. Second, the same monomers were polycondensed at 0–20 °C in the presence of pyridine. Third, dicarboxylic acid dichlorides and silylated BHET were polycondensed in bulk. Only this third method gave satisfactory molecular weights. Matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry revealed that the copolyesters prepared by the pyridine and silyl methods might have contained considerable fractions of cyclic oligoesters and polyesters despite the absence of transesterification and backbiting processes. The alternating sequences and thermal properties were characterized with ¹H NMR spectroscopy and differential scanning calorimetry measurements, respectively. In agreement with the alternating sequence, all copolyesters proved to be crystalline, but the crystallization was extremely slow [slower than that of poly(ethylene terephthalate)]. A second series of alternating copolyesters was prepared by the polycondensation of silylated bis(4‐hydroxybut‐ yl)terephthalate with various aliphatic dicarboxylic acid dichlorides. The resulting copolyesters showed significantly higher rates of crystallization, and the melting temperatures were higher than those of the BHET‐based copolyesters. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3371–3382, 2001     

Novel aromatic polyhydrazides and poly(amide-hydrazide)s based on “multiring” flexible dicarboxylic acids

Two flexible dicarboxylic acid monomers, 4,4′-[isopropylidenebis(1,4-phenylene)dioxy]dibenzoic acid ( 1 ) and 4,4′-[hexafluoroisopropylidenebis(1,4-phenylene)-dioxy]dibenzoic acid ( 3 ), were synthesized from readily available compounds in two steps in high yields. High molecular-weight polyhydrazides and poly(amide-hydra-zide)s were directly prepared from dicarboxylic acids 1 and 3 with terephthalic dihydrazide ( 5 ), isophthalic dihydrazide ( 6 ), and p-aminobenzhydrazide ( 7 ) by the phosphorylation reaction by means of diphenyl phosphite (DPP) and pyridine in N-methyl-2-pyrrolidone (NMP)/LiCl, or prepared from the diacyl chlorides of 1 and 3 with the hydrazide monomers 5–7 by the low-temperature solution polycondensation in NMP/LiCl. Less favorable results were obtained when using triphenyl phosphite (TPP) instead of DPP in the direct polycondensation reactions. Except for those derived from terephthalic dihydrazide, the resulting polyhydrazides and poly(amide-hydrazide)s could be cast into colorless, flexible, and tough films with good tensile strengths. All the hydrazide polymers and copolymers are amorphous in nature and are readily soluble in various polar solvents such as NMP and dimethyl sulfoxide (DMSO). Their T_gs were recorded in the range of 162–198°C and could be thermally cyclodehydrated into the corresponding polyoxadiazoles and poly(amide-oxadiazole)s approximately in the region of 300–380°C, as evidenced by the DSC thermograms. The oxadiazole polymers and copolymers showed a dramatically decreased solubility and higher T_g when compared to their respective hydrazide prepolymers. They exhibited T_gs of 190–216°C and were stable up to 450°C in air or nitrogen. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1847–1854, 1998     

Wholly aromatic thermotropic liquid crystalline polyesters of 4,4′-biphenol,substituted biphenols,and 1,1′-binaphthyl-4,4′-diol with 3,4′-benzophenone dicarboxylic acid

Wholly aromatic, thermotropic homopolyesters, derived from 4,4′-biphenol, substituted biphenols, or 1,1′-binaphthyl-4,4′-diol and 3,4′-benzophenone dicarboxylic acid, and two copolyesters, each of which contained 30 mol % of 6-hydroxy-2-naphthoic acid, were prepared by acidolysis polycondensation reactions and characterized for their liquid crystalline properties. The solubility behavior of these polymers has also been investigated. The two homopolymers of phenyl-substituted biphenols with 3,4′-benzophenone dicarboxylic acid were soluble in many common organic solvents. All of the homopolymers had lower T_m/T_f values than those with terephthalic acid, which was attributed to the incorporation of the asymmetric 3,4′-benzophenone dicarboxylate units in a head-to-head and head-to-tail fashion along the polyester chain. Two copolymers had lower T_m values than those of the respective homopolymers, as expected. They formed nematic phases which persisted up to 400°C, except those of phenyl-substituted biphenols with 3,4′-benzophenone dicarboxylic acid. Each of these two polymers also exhibited an accessible T_i transition, and had a broad range of LC phase. They had glass transition temperatures, T_g, in the range of 139-209°C and high thermal stabilities in the temperature range of 465-511°C. © 1995 John Wiley & Sons, Inc.     

Fully aromatic thermotropic liquid crystalline homopolyesters of 3,4′-benzophenone dicarboxylic acid

A series of fully aromatic, thermotropic homopolyesters, derived from 3,4′-benzophenone dicarboxylic acid and various aromatic diols, was prepared by the melt polycondensation method and examined for thermotropic behavior by a variety of experimental techniques. The aromatic diols used in the study were hydroquinone, 2,6-, 1,4-, 1,5-, 2,3-, and 2,7-naphthalenediol isomers. All of the homopolyesters of 3,4′-benzophenone dicarboxylic acid with aromatic diols (except that with 2,7-naphthalenediol) formed a nematic LC phase in the melt. They had the glass transition temperatures (T_g) in the range of 133–164°C, the melting transitions (T_m) in the range 305–360°C and the high thermal stabilities (T_d) in the range of 410–483°C. The 2,6-naphthalenediol based homopolymer had the highest T_m (360°C) and the 2,3-naphthalenediol based homopolymer had the lowest T_m (305°C) among all of the homopolymers of naphthalenediol isomers. © 1994 John Wiley & Sons, Inc.     

Fully aromatic thermotropic liquid crystalline polyesters of 3-phenyl-4,4′-biphenol with 4,4′-benzophenone dicarboxylic acid

A series of fully aromatic, thermotropic polyesters, derived from 3-phenyl-4,4′-biphenol (MPBP), nonlinear 4,4′-benzophenone dicarboxylic acid (4,4′-BDA), and various other comonomers was prepared by the melt polycondensation method and characterized for their thermotropic liquid crystalline behavior by a variety of experimental techniques. The homopolymer of MPBP with 4,4′-BDA had a fusion temperature (T_f) at 240°C, exhibited a nematic liquid crystalline phase, and had a narrow liquid crystalline range of 60°C. All of the copolyesters of MPBP with 4,4′-BDA and either 30 mol % 4-hydroxybenzoic acid (HBA), 6-hydroxy-2-naphthoic acid (HNA) or 50 mol % terephthalic acid (TA), 2,6-naphthale-nedicarboxylic acid (2,6-NDA) and low T_f values in the range of 210–230°C, exhibited a nematic phase, and had accessible isotropization transitions (T_i) in the range of 320–420°C, respectively. As expected, each of them had a broader range of liquid crystalline phase than the homopolymer. They had a “frozen” nematic, glassy order as determined with the wide-angle X-ray diffraction (WAXD) studies. The morphology of each of the “as-made” polyesters had a fibrous structure as determined with the scanning electron microscopy (SEM), which arises because of the liquid crystalline domains. Moreover, they had higher glass transition temperatures (T_g) in the range of 167–190°C than those of other liquid crystalline polyesters, and excellent thermal stabilities (T_d) in the range of 500–533°C, respectively. © 1995 John Wiley & Sons, Inc.     

New polymer syntheses. LXVI. Copolyester of 4-hydroxybenzoic acid and 3-(4'-hydroxyphenoxy)benzoic acid or 4-(3'-hydroxyphenoxy)benzoic acid

Copolyesters of 4-hydroxybenzoic acid (HBA) and 3-(4'-hydroxyphenoxy)benzoic acid were prepared by two different procedures. Either the acetyl derivatives were polycondensed in bulk at temperatures up to 300°C or they were polycondensed in an inert reactions medium (Marlotherm-S) at 340°C. Two analogous series of copolyesters were synthesized from 4-acetoxybenzoic acid (4-HBA) and 4-(3'-acetoxyphenoxy)benzoic acid. The copolyesters were characterized by elemental analyses, inherent viscosities, ¹H- and ¹³C-NMR spectroscopy, WAXS and DSC measurements, and by optical microscopy. All copolyesters synthesized in solution were highly crystalline materials which were neither meltable nor soluble. Part of the copolyesters prepared by polycondensation in bulk were semi-crystalline, meltable, and soluble. The copolyester derived from 3-(4'-hydroxyphenoxy)benzoic acid proved to be thermotropic forming a nematic melt, whereas the isomeric copolyesters of 4-(3'-hydroxyphenoxy)benzoic acid only formed isotropic melts. © 1993 John Wiley & Sons, Inc.     

Synthesis of polyesters having quaternary ammonium groups in the side chains and preparation of their blends with poly(vinyl alcohol)

Triethyl-2,3-propanediolammonium chloride (TPC) was prepared and used for the preparation of polyester and copolyesters having quaternary ammonium groups in the side chains. The polycondensation of isophthaloyl dichloride with TPC and other dihydroxy compounds was performed by the organic phase/organic phase interfacial polycondensation method using N,N-dimethylacetamide/n-heptane or trimethyl phosphate/n-heptane as reaction media in the presence of tetramethyl ethylenediamine. Blend films were prepared from these polyesters and poly(vinyl alcohol) by casting from aqueous or aqueous NaOH solution. The electrical conductivity of the blend films is remarkably affected by the moisture content and in the order of 10^?5 ～ 10^?8 S/cm in the presence of moisture. © 1994 John Wiley & Sons, Inc.     

Wholly aromatic thermotropic liquid crystalline polyesters of 3,3′-bis(phenyl)-4,4′-biphenol with 4,4′-benzophenone dicarboxylic acid

A series of wholly aromatic, thermotropic polyesters, derived from 3,3′-bis(phenyl)-4,4′-biphenol (DPBP), nonlinear 4,4′-benzophenone dicarboxylic acid (4,4′-BDA), and various linear comonomers, were prepared by the melt polycondensation reaction and characterized for their thermotropic properties by a variety of experimental techniques. The homopolymer of DPBP with 4,4′-BDA had a fusion temperature (T_f) at 265°C, exhibited a nematic phase, and had a liquid crystalline range of 105°C. All of the copolyesters of DPBP with 4,4′-BDA and either 30 mol % 4-hydroxybenzoic acid (HBA), 6-hydroxy-2-naphthoic acid (HNA), or 50 mol % terephthalic acid (TA), 2,6-naphthalenedicarboxylic acid (2,6-NDA) had low T_f values in the range of 220–285°C, exhibited a nematic phase, and had accessible isotropization transitions (T_i) in the range of 270–420°C, respectively. Their accessible T_i values would enable one to observe a biphase structure. Each of the copolymers with HBA or HNA had a much broader range of liquid crystalline phase. In contrast, each of the copolymers with TA or 2,6-NDA had a relatively narrow range of liquid crystalline phase. Each of these polyesters had a glassy, nematic morphology that was confirmed with the DSC, PLM, WAXD, and SEM studies. As expected, they had higher glass transition temperatures (T_g) in the range of 161–217°C than those of other liquid crystalline polyesters, and excellent thermal stabilities (T_d) in the range of 494–517°C, respectively. Despite their noncrystallinity, they were not soluble in common organic solvents with the exception that the homopolymer and its copolymer with TA had limited solubility in CHCl₃. However, they were soluble in the usual mixture of p-chlorophenol/1,1,2,2-tetrachloroethane (60/40 by weight) with the exception of the copolymer with 2,6-NDA. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 769–785, 1997     

Preparation of phosphorus-containing polymers. XXV. Polyamide-imides that contain phenoxaphosphine rings

New phenoxaphosphine-containing polyamide-imides were prepared by cyclodehydration of the polyamide-amic acids obtained from 8-chloroformyl-10-phenylphenoxaphosphine-2,3-dicarboxylic anhydride 10-oxide and diamines by a low-temperature solution polycondensation. Polymers with reduced viscosities of 0.10–0.59 dl/g in DMA or concentrated H₂SO₄ at 30°C were obtained in 64–97% yields. All the polyamide-imides were soluble in m-cresol, concentrated H₂SO₄, and dichloroacetic acid and some of them were soluble in DMF, DMA, and DMSO; the polyamide-imides had better solubility in organic solvents than phenoxaphosphine-containing polyimides. The phenoxaphosphine-containing polyamide-imides derived from aromatic diamines exhibited excellent thermal properties and little degradation below about 400°C, whereas the polymers from aliphatic diamines began to lose weight at about 250°C. They appeared to have thermal stability between phenoxaphosphine-containing polyimides and polyamides. These polyamide-imides exhibited self-extinguishing behavior.     

Polyamide synthesis by the direct polycondensation with phenylphosphonic dichloride in pyridine

The direct polycondensation of isophthalic acid (IPA) and aromatic diamines with a new phosphorus compound, phenylphosphonic dichloride (PPDC), was studied. PPDC could actually react with nearly a two molar amount of carboxyl groups, but more than 75 mol % PPDC with respect to the carboxyl groups of IPA were satisfactorily used in the polycondensation. The initial reaction of IPA with PPDC in pyridine at room temperature and then at 120°C was needed to complete the activation, and the subsequent aminolysis at 120°C for 3 h was most effective. The polyamides of high inherent viscosity were obtained even from weakly basic aromatic diamines, and their values were more than those obtained by the conventional method. In their thermal properties determined by the DTA, they showed T_gs and T_ms higher than those reported before.     

Synthesis and structure of biodegradable hexylene terephthalate-co-lactide copolyesters

To obtain a biodegradable polymer material with satisfactory thermal properties, higher elongation and modulus of elasticity, a new copolyester, poly(hexylene terephthalate-co-lactide) (PHTL), was synthesized via direct polycondensation from terephthaloyl dichloride, 1,6-hexanediol and oligo(lactic acid). The resulting copolyesters were characterized by proton nuclear magnetic resonance (¹H NMR), differential scanning calorimetry (DSC), thermogravimetry (TG) and wide-angle X-ray scattering (WAXS). By using the relative integral areas of the dyad peaks in ¹H NMR spectrum of copolyesters PHTL, the sequence lengths of the hexylene terephthalate and lactide units in the resultant copolyesters are 3.5 and 1.5, respectively. Compared to poly(hexylene terephthalate) (PHT), PHTL has lower T _m but higher T _g due to the incorporation of lactide unit into the main chains of copolyesters. The degradation test of copolyesters under a physiological condition shows that the degradability of PHTL is sped up due to incorporation of lactide segments.     

Direct dehydration polycondensation of lactic acid catalyzed by water‐stable Lewis acids

Poly(L ‐lactic acid) (PLLA) is generally produced by ring‐opening polymerization of (S,S)‐lactide, which is prepared from dehydration polycondensation of lactic acid and successive depolymerization. Results of this study show that scandium trifluoromethanesulfonate [Sc(OTf)₃] and scandium trifluoromethanesulfonimide [Sc(NTf₂)₃] are effective for one‐step dehydration polycondensation of L ‐lactic acid. Bulk polycondensation of L ‐lactic acid was carried out at 130–170 °C to give PLLA with M_n of 5.1 × 10⁴ to 7.3 × 10⁴ (yield 32–60%). The solution polycondensation was performed at 135 °C for 48 h to afford PLLA with M_n of 1.1 × 10⁴ with good yield (90%). In no case did ¹H NMR, specific optical rotation, or DSC measurement confirm racemizations. The catalyst was recovered easily by extraction with water and reused for polycondensation. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5247–5253, 2006     

Synthesis and characterization of novel renewable polyesters based on 2,5‐furandicarboxylic acid and 2,3‐butanediol

Novel polyesters from 2,5‐furandicarboxylic acid or 2,5‐dimethyl‐furandicarboxylate and 2,3‐butanediol have been synthesized via bulk polycondensation catalyzed by titanium (IV) n‐butoxide, tin (IV) ethylhexanoate, or zirconium (IV) butoxide. The polymers were analyzed by size exclusion chromatography, nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy (FTIR), matrix‐assisted laser ionization‐desorption time‐of‐flight mass spectrometry, electrospray ionization time‐of‐flight mass spectrometry, electrospray ionization quadruple time‐of‐flight mass spectroscopy, thermogravimetric analysis, and differential scanning calorimetry. Fully bio‐based polyesters with number average molecular weights ranging from 2 to 7 kg/mol were obtained which can be suitable for coating applications. The analysis of their thermal properties proved that these polyesters are thermally stable up to 270–300 °C, whereas their glass transition temperature (T_g) values were found between 70 and 110 °C. Furthermore, a material was prepared with a molecular weight of 13 kg/mol, with a T_g of 113 °C. This high T_g would make this material possibly suitable for hot‐fill applications. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Fully aromatic thermotropic liquid crystalline polyesters of substituted 4,4′-biphenols. IV. Homopolyesters with terephthalic acid and copolyesters with terephthalic acid and 4-hydroxybenzoic acid

A series of fully aromatic thermotropic polyesters based on mono-, di-, and tetra-substituted biphenols was prepared by the melt polycondensation method and examined for their thermotropic behavior by a variety of experimental techniques. The homopolyesters obtained from substituted biphenols containing either one phenyl or two phenyl groups as substituent(s) and TA formed nematic melts, but the homopolymers of the substituted biphenols containing either four sec-butyl groups or two tert-butyl groups with TA had melting transitions, T_m, above 400°C. Thus, it was not possible to determine whether they formed nematic melts. On copolymerization with 30 mol % HBA most of the resulting copolyesters had much lower T_m values, compared to those of respective homopolyesters, and the copolymers of the biphenol monomer containing the tert-butyl groups formed a nematic melt at an observable temperature. However, the copolymer of the biphenol with sec-butyl groups still had a T_m above 400°C. © 1993 John Wiley & Sons, Inc.