Blends of different linear polyamides with hyperbranched aromatic AB2 and A2 + B3 polyesters

To explore the possible applications of hyperbranched polymers for modifying linear polyamides, two hyperbranched aromatic polyesters characterized as high T_g polymers possessing phenolic end groups were used in melt mixing with partly aromatic polyamide and commercially available aliphatic polyamide‐6, respectively. Different amounts of both hyperbranched polyesters (from 1 wt % up to 20 wt %) were added to the polyamides, and the influence of these hyperbranched polyesters on the properties of the polyamides was investigated. The hyperbranched polyester based on an AB₂ approach was found to be the most effective modifier. A significant increase of the glass transition temperature of the final blend was detected. However, a remarkable reduction of crystallinity as well as complex melt viscosity of those blends was also observed. The use of an A₂+B₃ hyperbranched polyester as melt modifier for the polyamides was less effective for changing the thermal properties, and the complex melt viscosity of the final material increased since heterogeneous blends were formed. In contrast to that, generally, the addition of the AB₂ hyperbranched polyester to the polyamides resulted in homogeneous blends with improved T_g and processability. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3558–3572, 2009     

Synthesis and characterization of poly(2,5‐furan dicarboxylate)s based on a variety of diols

Novel polyesters from renewable resources based on 2,5‐dicarboxylic acid and several diols were synthesized and characterized using different polycondensation techniques. The aliphatic diols were sufficiently volatile to allow the use of polytransesterifications, which gave high‐molecular weight semicrystalline materials with good thermal stability. In particular, the polyester based on ethylene glycol displayed properties comparable with those of its aromatic counterpart, poly(ethylene terephthalate), namely, the most important industrial polyester. The use of isosorbide gave rise to amorphous polymers with very stiff chains and hence a high glass transition temperature and an enhanced thermal stability. The interfacial polycondensation between the acid dichloride and hydroquinone produced a semicrystalline material with features similar to those of entirely aromatic polyesters, characterized essentially by the absence of melting and poor solubility, both associated with their remarkable chain rigidity. The replacement of hydroquinone with the corresponding benzylic diol was sufficient to provide a more tractable polyester. This study provided ample evidence in favor of the exploitation of furan monomers as renewable alternatives to fossil‐based aromatic homologs. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis,thermal, rheological characteristics,and enzymatic degradation of aliphatic polyesters with lignin‐based aromatic pendant groups

This research aims to produce lignin‐based biodegradable polyesters with improved thermal quality. A series of aliphatic polyesters with lignin‐based aromatic side groups were synthesized by conventional melt‐polycondensation. Decent molecular weight (21–64 kg mol^?1) was achieved for the polymerizations. The molecular structures and thermal and mechanical properties of the obtained polyesters were characterized. As a result, the obtained polyesters are all amorphous, and their glass‐transition temperature (T_g) depends on the size of the pendant aromatic group (31–51 °C). Furthermore, according to the TGA results, the thermal decomposition temperatures of the polyesters are all above 390 °C, which make them superior compared with commercial biodegradable polyesters like polylactic acid or polyhydroxyalkanoates. Finally, rheological characteristics and enzymatic degradation of the obtained polyesters were also measured. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 2314–2323     

Design and Synthesis of Aromatic Polyesters Bearing Pendant Clickable Maleimide Groups

A bisphenol bearing pendant maleimide group, namely, N‐maleimidoethyl‐3, 3‐bis(4‐hydroxyphenyl)‐1‐isobenzopyrrolidone (PPH‐MA) was synthesized starting from phenolphthalein. Aromatic (co)polyesters bearing pendant maleimide groups were synthesized from PPH‐MA and aromatic diacid chlorides, namely, isophthaloyl chloride (IPC), terephthaloyl chloride (TPC), and 50:50 mol % mixture of IPC and TPC by low temperature solution polycondensation technique. Copolyesters were also synthesized by polycondensation of different molar proportions of PPH‐MA and bisphenol A with IPC. Inherent viscosities and number‐average molecular weights of aromatic (co)polyesters were in the range of 0.52–0.97 dL/g and 20,200–32,800 g/mol, respectively indicating formation of medium to reasonably high‐molecular‐weight polymers. ¹³C NMR spectral analysis of copolyesters revealed the formation of random copolymers. The 10% weight loss temperature of (co)polyesters was found in the range 470–484 °C, indicating their good thermal stability. A selected aromatic polyester bearing pendant maleimide groups was chemically modified via thiol‐maleimide Michael addition reaction with two representative thiol compounds, namely, 4‐chlorothiophenol and 1‐adamantanethiol to yield post‐modified polymers in a quantitative manner. Additionally, it was demonstrated that polyester containing pendant maleimide groups could be used to form insoluble crosslinked gel in the presence of a multifunctional thiol crosslinker. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 630–640     

A series of furan‐aromatic polyesters synthesized via direct esterification method based on renewable resources

A series of furan‐aromatic polyesters were successfully synthesized via direct esterification method starting from 2,5‐furandicarboxylic acid, ethylene glycol, 1,3‐propanediol, 1,4‐butanediol, 1,6‐hexanediol, and 1,8‐octanediol and characterized by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (¹H NMR), X‐ray diffraction (XRD), differential scanning calorimeter (DSC), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), tensile tests, and so on. The preliminary evidence clearly showed that direct esterification method was rewarding and worthy to synthesize these furan‐aromatic polyesters. The densities of furan‐aromatic polyesters were ranging from 1.19 to 1.38 kg/m³. The FTIR and ¹H NMR confirmed their expected structures in detail. The results of XRD showed that these furan‐aromatic polyesters were crystalline polyesters. The results of DSC, TGA, DMA, and tensile tests showed that they behaved as thermoplastic polyester, had satisfactory thermal and mechanical properties, and their thermal stabilities were quite similar to that of corresponding benzene‐aromatic polyesters. The results of contact angle measurement showed that they were hydrophilic. The properties above showed that furan‐aromatic polyesters based on renewable resources could be a viable alternative to their successful petrochemical benzene‐aromatic counterpart. Furthermore, they could be used as biopolymer materials according their satisfactory thermal and mechanical properties and hydrophilicity in the future. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Novel thermotropic esters‐based polymers with broad nematic processing windows

In this study, a new series of semiflexible liquid crystalline (LC) polyesters and poly(ester‐amide)s were synthesized and characterized. Polymers based on 4‐hydroxybenzoic acid (4‐HBA), 6‐hydroxy‐2‐naphthoic acid (HNA), suberic acid (SUA), and sebacic acid (SEA) were modified with hydroquinone (HQ) and different concentrations of 4‐acetamidophenol (AP) to obtain a polyester and two poly(ester‐amide)s, respectively. All polymers were successfully prepared using conventional melt‐condensation techniques. The polymers were characterized by inherent viscosity measurements, SEC, hot‐stage polarizing microscopy, DSC, and TGA. The mechanical behavior was investigated using DMTA and tensile testing. All linear polymers have T_gs in the range of 50–80 °C and melt between 120 and 150 °C. Our polymers display good thermooxidative stabilities (5% wt loss at ～ 400 °C) and exhibit homogeneous nematic melt behavior over a wide temperature range (ΔN ～ 250 °C). The liquid crystal phase was lost when high concentrations of nonlinear monomers such as 3‐HBA (>27 mol %) and resorcinol (RC) (>23 mol %) were incorporated. The LC polyester based on 4‐HBA/HNA/HQ/SUA/SEA could easily be processed into good quality films and fibers. The films display good mechanical properties (E′ ～ 4 GPa) and high toughness, that is, ～ 15% elongation at break, at room temperature. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6565–6574, 2008     

Aromatic polyesters from naturally occurring monosaccharides: Poly(ethylene terephthalate) and poly(ethylene isophthalate) analogs derived from D‐mannitol and galactitol

The synthesis and characterization of a new series of aromatic polyesters based on D‐mannitol and galactitol are described. These polyesters were obtained by polycondensation reaction of the terephthaloyl chloride or isophthaloyl chloride and 2,3,4,5‐tetra‐O‐methyl‐D‐mannitol or 2,3,4,5‐tetra‐O‐methyl‐galactitol in o‐dichlorobenzene. All the new polyesters were characterized by elemental analyses, GPC, IR, and NMR. They were soluble in chloroform, but insoluble in water and other polar oxygenated solvents. They showed a notable hygroscopicity, lower for those containing isophthalic units. DSC and X‐ray diffraction studies showed that D‐mannitol‐based polyesters were stiffer and less crystalline than those derived from galactitol, which presented a noticeably lower thermal stability. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4570–4577, 2005     

LCP aromatic polyesters by esterolysis melt polymerization

Polyarylates have previously been synthesized from acetate esters via esterolysis (loss of methyl acetate). This polycondensation can be extended to p‐substituted aromatic monomers for liquid crystal polyesters (LCPs). For AB‐type polymers, methyl p‐acetoxybenzoate and methyl 6‐acetoxynaphthoate were copolymerized to an LCP with reasonable molecular weights. Benzoate esters, methyl 4‐benzoyloxybenzoate (MBB) and methyl 6‐benzoyloxy‐2‐naphthoate (MBN), are also investigated. Several tin and antimony oxide catalysts were effective. The rate of esterolysis polymerization of MBB and MBN is slower than that of the corresponding acidolysis melt polymerization, but fast enough to give relatively high‐molecular‐weight polymers and similar thermal stability as commercial LCP prepared by acidolysis. Using these alternative benzoyloxy groups significantly reduced the color problem, because ketene loss cannot occur. Esterolysis melt polymerizations leading to AB/AABB‐type LCPs were performed using either dimethyl 2,6‐naphthalene dicarboxylate (DMND) or dimethyl terephthalate (DMT) with methyl 4‐acetoxybenzoate and phenylhydroquinone diacetate with tin and antimony catalysts. DMT‐based monomer compositions show much faster polymerization than DMND‐based compositions using antimony oxide catalyst. All these LCPs show a T_g in the 140–170 °C range as a result of the inclusion of the naphthalene and/or phenyl hydroquinone units in the polymer chain. Compositions completely off‐balanced on either side still lead to relatively high‐molecular‐weight copolyesters because either excess monomer can be removed during polymerization. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3586–3595, 2000     

Development of functional polymers with cyclic ether moieties. I. Synthesis and properties of polyesters with dioxane moiety in the main chain

A series of novel polyesters containing dioxane moieties in their main chains were synthesized by the bulk polycondensation of trans‐2,5‐bis‐(hydroxy‐ methyl)‐1,4‐dioxane with various aliphatic dicarboxylic acid chlorides. The obtained polyesters, analyzed by differential thermal analysis, possessed crystallinity, the melting point of which exhibited a weak odd–even effect on the methylene unit number and a small decreasing trend with an increase in the methylene unit number. These properties were compared with those of similar polyesters bearing cyclohexane moieties, and it was found that the rigidity of the dioxane moiety plays an important role in enhancing the effective packing of the corresponding polymers. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2536–2542, 2000     

Polyesters containing sulfur. VI. Synthesis and characterization of polyesters from naphthalene-1,4- or naphthalene-1,5-bis(methylthioacetic acid) and aliphatic diols

Two series of new linear polyesters containing sulfur in the main chain were obtained by melt polycondensation of naphthalene-1,4-bis(methylthioacetic acid) (N-1,4-BMTAA) or naphthalene-1,5-bis(methylthioacetic acid) (N-1,5-BMTAA) with some aliphatic diols using a 0.05 molar excess of diol. Softening temperatures ranging from 55 to 130°C, reduced viscosities in the range of 0.15–0.39 dL/g, and low-molecular weights were their characteristic. The structure and thermal properties of all polyesters were examined by using elemental analysis, FT-IR and ¹H-NMR spectroscopy, X-ray diffraction analysis, differential thermal analysis (DTA), thermogravimetric analysis (TGA), and differential scanning calorymetry (DSC). The kinetics of polyester formation by uncatalyzed melt polycondensation was studied in a model system: N-1,4-BMTAA or N-1,5-BMTAA and 2,2′-oxydiethanol (ODE) at 150, 160, and 170°C. Reaction rate constants (k₃) and activation parameters (ΔG^‡, ΔH^‡, ΔS^‡) from carboxyl group loss were determined using classical kinetic methods. Hydroxyl-terminated polyesters derived from 1,4-butanediol, 1,5-pentanediol, and 1,6-hexanediol were used for preparation of the polyurethanes by melt polyaddition with hexamethylene diisocyanate (HDI). They were characterized by reduced viscosity, FT-IR spectroscopy, X-ray diffraction analysis, TGA, DSC, polarizing microscope observation, and hardness and tensile properties. The resulting polyurethanes behave like high-elasticity thermoplastic elastomers, except the one derived from N-1,5-BMTAA and 1,6-hexanediol-based polyester. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2359–2369, 1998     

Fire‐Safe Polyesters Enabled by End‐Group Capturing Chemistry

Upon heating, polyesters decompose to small molecules and release flammable volatiles and toxic gases, primarily through chain scission of their ester linkages, and therefore exhibit poor fire‐safety properties, thus restricting their applications. Reported herein is an end‐group‐capturing effect of (bis)oxazoline groups, generated from the thermal rearrangement of the N‐(2‐hydroxyphenyl)phthalimide (HPI) moiety which was incorporated into the polyester chain by copolymerization. These copolyesters, as a result, exhibit high efficiency in retarding decomposition by capturing the decomposed products, particularly for the carbonyl‐terminated fragments, thus increasing the fire‐safety properties, such as self‐extinguishing, anti‐dripping, and inhibiting heat release and smoke production. The successful application of this method in both semi‐aromatic and aliphatic polyesters provide promising perspectives to designing versatile fire‐safe polymers.     

Hydrogen‐bonded thermotropic liquid‐crystalline polyester–amides from bis(hydroxy alkamido)aranes: Synthesis and properties

Hydrogen‐bonded aromatic–aliphatic polyester–amides (PEAs) were prepared by solution/melt polycondensation of aromatic–aliphatic amidodiols 1,4‐bis(4‐hydroxybutyramide)benzene (BHBB), 1,4‐bis(5‐hydroxy pentamide)benzene, 1,4‐bis(6‐hydroxyhexamide)benzene, 1,4‐bis(4‐hydroxybutyramidexylene), 1,4‐bis(5‐hydroxypentamidexylene, 1,4‐bis(4‐hydroxybutyramide)benzene, and 1,4‐bis(6‐hydroxyhexamidexylene) with terephthaloyl chloride/dimethyl terephthalate. Aromatic–aliphatic amido diols were prepared by the aminolysis of γ‐butyrolactone, δ‐valerolactone, and ?‐caprolactone with aromatic diamines such as paraphenylene diamine and paraxylene diamine. The monomers and polymers were characterized by chemical analysis (hydroxyl value and elemental analysis), Fourier transform infrared spectroscopy, ¹H NMR, and ¹³C NMR. The thermal‐ and phase‐transition behaviors of the polymers were investigated by differential scanning calorimetry in combination with hot‐stage optical microscopy. Crystallinity of polymers was examined with wide‐angle X‐ray diffraction. The polymers exhibited liquid crystallinity with layered structures formed by self‐organization of the hetero intermolecular hydrogen‐bonded networks indicating smectic phases except for PEAs prepared from BHBB. The hydrogen atom of the phenyl‐substituent group forces the neighboring carbonyl groups out of plane of the rings preventing formation of layered structures in the case of BHBB. The PEAs retained intermolecular hydrogen bonding even in the mesomorphic state, and variations in the hydrogen‐bonded lamellae/micelles might be responsible for the variations from one smectic to another texture. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 335–346, 2003     

Biodegradable network elastomeric polyesters from multifunctional aromatic carboxylic acids and poly(ϵ‐caprolactone) diols

Novel biodegradable network polyesters were prepared from multifunctional aromatic carboxylic acids [trimesic acid (Y), pyromellic acid (X), and mellic acid (Y_M)] and poly(?‐caprolactone) (PCL) diols with molecular weights of 530, 1250, and 2000. Prepolymers prepared by a melt polycondensation method were cast from dimethylformamide solutions and postpolymerized at 220 °C for various times to form a network. The resultant films were transparent, flexible, and insoluble in organic solvents. The network polyesters obtained were characterized by infrared absorption spectra, wide‐angle X‐ray diffraction analysis, density measurements, differential scanning calorimetry, thermomechanical analysis, and tensile testing. Some network polyester films, including YPCL_1250, XPCL₁₂₅₀, and Y_MPCL₂₀₀₀, showed elastomeric properties with high ultimate elongation and low tensile modulus. The enzymatic degradation was measured by the weight loss of the network polyester films in a buffer solution with Rhizopus delemar lipase at 37 °C. The degree and rate of degradation increased with the increasing molecular weight of the PCL diols, but they decreased in the order of YPCL > XPCL > Y_MPCL because of the increase in the crosslinking densities of the network films. The degraded products after enzymatic degradation showed that the ester linkage of the PCL component and the aromatic ester linkage between Y and PCL diols were hydrolyzed. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4523–4529, 2002     

Linear and A2+B3‐type hyperbranched polyesters comprising phenylbenzothiazole unit: Preparation,liquid crystalline,and optical properties

Novel liquid crystalline (LC) hyperbranched (HB) polyesters comprising phenylbenzothiazole (PBT) unit as mesogen in the interiors were prepared at various feed mole ratios (A₂/B₃) by solution polycondensation of a dioxydiundecanol derivative of PBT (A₂ monomer) with trimesic acid trimethyl ester (B₃ monomer) via A₂+B₃ approach and their LC and optical properties were investigated. Analogous linear polyesters containing the PBT unit in the main chains were also prepared by the solution polycondensation of A₂ monomer with aromatic or aliphatic dimethyl esters. FTIR and ¹H‐NMR spectroscopies indicated that the HB polyesters are produced without gelation during the polycondensation and have degree of branching (DB) of 7–46%. The structures of HB polymers changed depending on the feed mole ratios and the polymer prepared in the mole ratio of A₂/B₃ = 3/2 had the highest inherent viscosity and DB. Acetylation of terminal OH group‐having HB polyesters prepared in excess mole ratios of A₂/B₃ afforded ones bearing acetoxy groups in the terminals. DSC measurements, polarizing microscope observations of textures, and X‐ray analyses suggested that only the terminal OH group‐having HB polymer prepared in the mole ratio of A₂/B₃ = 3/1 form smectic C phase. In the linear polymers, the polymers derived by using the aromatic dimethyl esters had no LC melt, but those from the aliphatic dimethyl esters formed LC smectic C phase. The acetoxy group‐bearing HB polymers showed more stable smectic A or C phase than those with the OH terminals. Solution UV‐vis and photoluminescent (PL) spectra indicated that the linear and the HB polymers have analogous optical properties and display maximum absorbances and blue‐light emission on the basis of the PBT unit, where the Stokes shifts were observed because of intermolecular aggregation effects, but there is a large difference between the optical behaviors of the linear and the HB polymers in film, whose E_g values of the linear polymers decreased and those of the HB polymers vice versa. Quantum efficiencies (Φ) had a tendency of increase in the linear polymers and the HB polymers forming LC phases. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6688–6702, 2008     

Functional aliphatic polyesters and nanoparticles prepared by organocatalysis and orthogonal grafting chemistry

We describe the use of organic catalysis for the ring‐opening polymerization of functionalized lactones and conversion of the resulting aliphatic polyesters into crosslinked nanoparticles that carry additional functional groups amenable to further modification. Specifically, highly functional aliphatic polyester homopolymers, as well as random and block copolymers, were prepared by 1,5,7‐triazabicyclo[4.4.0]dec‐5‐ene catalysis, giving polyesters with pendent alkene and alkyne groups. Azide‐alkyne click and thiol‐ene chemistries were used for postpolymerization modification of diblock copolymers possessing alkene groups on one block and alkyne groups on the other block. The polyesters were crosslinked using azide/alkyne cycloaddition, by reaction of α,ω‐diazides with the pendent alkynes on the polyester backbone. This gave polyester nanoparticles possessing alkene functionality, which were subjected to further modification using thiol‐ene reactions to introduce additional functionality. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Synthesis,characterization, and biodegradability of novel regular‐network polyester‐amines based on 1,1,1‐triethanolamine

Regular‐network polyester‐amines were prepared from 1,1,1‐triethanolamine (Y_N) and various dicarboxylic acids [HOOC? (CH₂)_n?2? COOH, n = 6–14]. A prepolymer prepared by melt polycondensation was cast from dimethylformamide solution and postpolymerized at 220 °C in a nitrogen flow for various periods of time to form a network. The resultant films were transparent, flexible, and insoluble in organic solvents. The network polyester‐amines obtained were characterized by infrared absorption spectra, wide‐angle X‐ray diffraction analysis, density, DSC, and thermomechanical analysis. The biodegradation experiments for the network polyester‐amine films were carried out in enzymatic solution with Rhizopus delemar or Pseudomonas cepacia lipase and in an activated sludge. The degree and rate of biodegradation were estimated by the weight loss of the films. After incubation in Rhizopus delemar lipase solution for 24 h, weight loss was hardly observed for Y_N6–7, whereas it increased greatly for Y_N8–13 (13–51 g/m²), and then it decreased rapidly for Y_N14. The methylene‐chain dependence of degradation was essentially the same as in the case of network polyesters from glycerol and various aliphatic dicarboxylic acids reported previously. Psedomonas cepacia lipases also degraded Y_Nn films, but the rate of degradation was much slower than Rhizopus delemar lipase. In the exposure to activated sludge for 30 days, the network polyester films with medium methylene‐chain lengths (Y_N7–11) showed the lager weight loss, as in the case of the enzymatic degradation, whereas the rate of biodegradation was much slower than that of the enzymatic degradation with Rhizopus delemar lipase. The effect of the protonation of the film with hydrochloric acid on the enzymatic degradation was also examined. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2896–2903, 2001     

Nonlinear optical properties of regioregular main‐chain polyesters

We have prepared new polyesters containing quadratic, nonlinear optical (NLO) active chromophores covalently incorporated into the main chain. In these polymers, the sequence of the chromophore units along the main chain is rigorously head to tail. All the polyesters are processable, both in the melt and in solution. For one polyester, a full second‐order NLO characterization has been performed. An out‐of‐resonance d₃₃ coefficient of 21 pm/V at 1368 nm has been measured. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2719–2725, 2007     

Synthesis and characterization of hydrogen‐bonded thermotropic liquid crystalline aromatic‐aliphatic poly(ester–amide)s from amido diol

Fifteen highly regular hydrogen‐bonded, novel thermotropic, aromatic‐aliphatic poly(ester–amide)s (PEAs) were synthesized from aliphatic amido diols by melt polycondensation with dimethyl terephthalate and solution polycondensation with terephthaloyl chloride. Intermolecular hydrogen bonds more or less perpendicular to the main‐chain direction induce the formation and stabilization of liquid crystalline property for these PEAs. The structure of these polymers, even in the mesomorphic phase is dominated by hydrogen bonds between the amide–amide and amide–ester groups in adjacent chains. Aliphatic amido diols were synthesized by the aminolysis of γ‐butyrolactone, δ‐valerolactone and ε‐caprolactone with aliphatic diamines containing a number of methylene groups from two to six in isopropanol medium at room temperature. Effects of polarity of the solvent on solution polymerization and effect of catalyst on trans esterification were studied. These polymers were characterized by elemental analysis, FTIR, ¹H NMR, ¹³C NMR, solubility studies, inherent viscosity, DSC, X‐ray diffraction, polarized light microscopy, and TGA. All the melt/solution polycondensed PEAs showed multiple‐phase transitions on heating with second transitions identified as nematic/smectic/spherullitic texture. The mesomorphic properties were studied as a function of their chemical structure by changing alternatively m or n. Odd‐even effect on mesophase transition temperature, isotropization temperature, and crystallinity were studied. The effect of molecular weight and polydispersity on mesophase/isotropization temperature and thermal stability were investigated. It was observed that there exists a competition for crystallinity and liquid crystallinity in these PEAs © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2469–2486, 2000     

Aromatic homo‐ and copolyesters from naturally occurring monosaccharides: PET and PEI analogs derived from L‐arabinitol and xylitol

The synthesis and characterization of new aromatic homo‐ and copolyesters based on l‐arabinitol and xylitol are described. These polymers were obtained by polycondensation reaction of the 2,3,4‐tri‐O‐methyl‐l‐arabinitol or 2,3,4‐tri‐O‐methyl‐xylitol, or their mixtures with ethylene glycol, with terephthaloyl chloride or isophthaloyl chloride in o‐dichlorobenzene or in the melt phase from the corresponding methyl phthalates. All the polymers were characterized by GPC, IR, and NMR. Their M_w values ranged between 11,500 and 46,500, with polydispersities from 1.5 to 2.3. They were found to be soluble in chloroform, but insoluble in water. In contrast with the homopolymers completely made with EG, they showed a significant hygroscopicity. DSC and TGA studies showed that the melting temperature of polyethylene terephthalate is depressed by the presence of pentitol units, whereas the thermal stability is kept above 350 °C. Only copolyesters containing 10% or less of pentitol units showed melting and produced X‐ray diffraction patterns characteristic of crystalline material. d‐Arabinitol‐based homopolyesters appeared to be more crystalline than those derived from xylitol and also presented a higher thermal stability. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6394–6410, 2005     

Polyesters containing sulfur. VII. New aliphatic‐aromatic polyesters for synthesis of polyester‐sulfur compositions and polyurethanes

New linear polyesters containing sulfur in the main chain were obtained by melt polycondensation of diphenylmethane‐4,4′‐bis(methylthioacetic acid) (DBMTAA) or diphenylmethane‐4,4′‐bis(methythiopropionic acid) (DBMTPA) and diphenylmethane‐4,4′‐bis(methylthioethanol) (DBMTE) at equimolar ratio of reagents (polyesters E‐A and E‐P) as well as at 0.15 molar excess of diol (polyesters E‐A_OH and E‐P_OH). The kinetics of these reactions was studied at 150, 160, and 170°C. Reaction rate constants (k₂) and activation parameters (ΔG^≠, ΔH^≠, ΔS^≠) from carboxyl group loss were determined using classical kinetic methods. E‐A and E‐P (M̄_n = 4400, 4600) were used for synthesis of new rubber‐like polyester‐sulfur compositions, by heating with elemental sulfur, whereas oligoesterols E‐A_OH and E‐P_OH (M̄_n = 2500, 2900) were converted to thermoplastic polyurethane elastomers by reaction with hexamethylene diisocyanate (HDI) or methylene bis(4‐phenyl isocyanate) (MDI). The structure of the polymers was determined by elemental analysis, FT‐IR and liquid or solid‐state ¹H‐, ¹³C‐NMR spectroscopy, and X‐ray diffraction analysis. Thermal properties were measured by DTA, TGA, and DSC. Hardness and tensile properties of polyurethanes and polyester‐sulfur compositions were also determined. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 835–848, 1999