Synthesis and characterization of polyesters based on 1,1,1‐[bis(4‐hydroxyphenyl)‐4′‐pentadecylphenyl]ethane

Aromatic polyesters are of considerable interest because of their excellent mechanical properties, chemical resistance and thermal stability. However, most aromatic polyesters are difficult to process due to their high glass transition temperatures coupled with their insolubility in common organic solvents. The present article describes a series of organosoluble polyesters and copolyesters based on 1,1,1‐[bis(4‐hydroxyphenyl)‐4′‐pentadecylphenyl]ethane. A series of new aromatic polyesters containing pendant pentadecyl chains was synthesized by interfacial polycondensation of 1,1,1‐[bis(4‐hydroxyphenyl)‐4′‐pentadecylphenyl]ethane with terephthalic acid chloride (TPC), isophthalic acid chloride (IPC) and a mixture of TPC and IPC. A series of copolyesters was synthesized from 4,4′‐isopropylidenediphenol with TPC by incorporating 1,1,1‐[bis(4‐hydroxyphenyl)‐4′‐pentadecylphenyl]ethane as a comonomer. Inherent viscosities of the polyesters and copolyesters were in the range 0.72–1.65 dL g^?1 and number‐average molecular weights were in the range 18 170–87 220. The polyesters and copolyesters containing pendant pentadecyl chains dissolved readily in organic solvents such as chloroform, dichloromethane, pyridine and m‐cresol and could be cast into transparent, flexible and apparently tough films. Wide‐angle X‐ray diffraction data revealed the amorphous nature of the polyesters and copolyesters. The formation of loosely developed layered structure was observed due to the packing of pendant pentadecyl chains. The temperature at 10% weight loss, determined using thermogravimetric analysis in nitrogen atmosphere, of the polyesters and copolyesters containing pendant pentadecyl chains was in the range 400–460 °C. The polyesters and copolyesters exhibited glass transition temperatures in the range 63–82 °C and 177–183 °C, respectively. Copyright © 2010 Society of Chemical Industry     

Synthesis of hexafluoroisopropylidene isophthalic polyesters and copolyesters and the relationship between their structure and gas transport properties

Two aromatic polyesters and three copolyesters were synthesized by interfacial polycondensation using 4,4′‐(hexafluoroisopropylidene)diphenol (HFD) and two phthalic dichlorides, isophthaloyl dichloride (ISO) and 5‐tertbutyl‐isophthaloyl dichloride (TERT). The polymers obtained were soluble in common chlorinated solvents. The properties of these aromatic polyesters and copolyesters were characterized by FTIR, density, inherent viscosity, TGA, and DSC. Thermal properties such as glass transition temperature, onset of decomposition, and thermal stability of the homopolymer, poly(hexafluoroisopropilydene)5‐tertbutylisophthalate (HFD/TERT), were higher than those of homopolymer poly(hexafluoroisopropilydene)isophthalate (HFD/ISO). Thermal properties of the copolyesters HFD/TERT‐co‐HFD/ISO depend upon the amounts of the tertbutyl group HFD/TERT, present in the copolymer. Gas permeability coefficients of all polyarylates were measured at 35°C. The effect of different concentrations of the bulky tertbutyl group at the 5‐position in the isophthaloyl moiety on He, O₂, N₂, and CO₂ permeability, diffusion, and solubility coefficients were determined. Gas permeability and diffusivity increase as the concentration of TERT moiety increases in the copolymers. The results indicate that polymers containing the largest amounts of the bulky lateral tertbutyl group show the highest gas permeability. The increment in gas permeability and diffusivity produces a decrease in selectivity, which is attributed to the effect of the large pendant tertbutyl groups in the aromatic polyesters and copolyesters, which decrease the chain packing efficiency and induce a larger fractional free volume. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2207–2216, 2007     

Synthesis,characterization, and acoustic properties of new soluble polyurethanes based on 2,2′‐[1,4‐phenylenebis(nitrilomethylylidene)diphenol and 2,2′‐[4,4′‐methylene‐di‐2‐methylphenylene‐1,1′‐bis(nitrilomethylylidene)]diphenol

Eight novel polyurethanes based on 2,2′‐[1,4‐phenylenebis(nitrilomethylylidene)]diphenol and 2,2′‐[4,4′‐methylene‐di‐2‐methylphenylene‐1,1′‐bis(nitrilomethylylidene)]diphenol acting as hard segments with two aromatic and two aliphatic diisocyanates (4,4′‐diphenylmethane diisocyanate, toluene 2,4‐diisocyanate, isophorone diisocyanate, and hexamethylene diisocyanate) were prepared and characterized with Fourier transform infrared, UV spectrophotometry, fluorescence spectroscopy, ¹H‐NMR and ¹³C‐NMR spectroscopy, thermogravimetric analysis, and differential thermal analysis. All the polyurethanes contained domains of semicrystalline and amorphous structures, as indicated by X‐ray diffraction. The acoustic properties and solubility parameters were calculated with the group contribution method. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Poly(ethylene terephthalate‐co‐isophthalate) copolyesters obtained from ethylene terephthalate and isophthalate oligomers

A series of poly(ethylene terephthalate‐co‐isophthalate) copolyesters containing upto 50%‐mole of isophthalic units were prepared by polycondensation from ethylene terephthalate and ethylene isophthalate fractions of linear oligomers containing from 5 to 6 repeating units in average. The polyesters were obtained in good yields and with high‐molecular‐weights. The microstructure of the copolyesters was studied as a function of reaction time by ¹³C‐NMR showing that a random distribution of the comonomers was achieved since the earlier stages of polycondensation. The melting temperature and enthalpy of the copolyesters decreased with the content of isophthalic units so that copolyesters containing more than 25% of these units were amorphous. Isothermal crystallization studies made on crystalline copolyesters revealed that the crystallization rate of copolyesters decreased with the content in isophthalic units. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Linear polymers with sulfur in the main chain. II. Synthesis of polyesters by interfacial polycondensation of bis(4,4′‐hydroxyphenyl)sulfide with several aliphatic acid dichlorides and their properties

The synthesis and properties of sulfur‐containing polyesters derived from bis(4,4′‐hydroxyphenyl)sulfide (TDP) and various acid dichlorides (AC) have been studied to evaluate the effect of the incorporation of sulfur in the main chains of polyesters. Polyesters derived from TDP and AC (with methylene numbers of 2–10) were synthesized by interfacial polycondensation in a 1,1,2,2‐tetrachloroethane /water mixture using tetra‐n‐butyl ammonium bromide as a phase transfer catalyst. Through the use of gel permeation chromatography, it was determined that the polyesters thus obtained had high molecular weights. The thermal properties of the polyesters including the TDP moiety were evaluated by thermogravimetry/differential thermal analysis and by differential scanning calorimetry. The analyses indicated that the polyesters including the TDP moiety were crystalline polymers with relatively high heat resistance. These polyesters were found to show an odd–even effect with the glass transition temperature and the melting point based on the methylene numbers. The tensile strength and storage modulus decreased with the methylene numbers. It was further found that the polyesters evidenced excellent barrier properties towards oxygen gas having an odd–even effect. In particular, it was shown that the polyesters with methylene numbers of 3, 4, 6, and 8 of methylene units have lower oxygen permeability than poly(ethylene terephthalate) (PET).©2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1865–1872, 2004     

Synthesis and modification of aromatic polyesters with chloroacetyl 3,5‐dibromo‐p‐hydroxybenzoic acid

Aromatic copolyesters based on diphenylolpropane and 3,5‐dibromo‐p‐hydroxybenzoic acid (p‐HBA) were synthesized by an acceptor‐catalyzed polycondensation method. During the synthesis, equimolar mixtures of chloranhydrides of isophthalic and terephthalic acids were used. The effects of p‐HBA on the tensile and thermal properties of the polyesters were investigated. The breaking stress and modulus of elasticity increased with the amount of p‐HBA up to 10% in molar mass. A further increase in p‐HBA caused deterioration of the tensile properties. The elongation at break decreased at low p‐HBA contents (<5%). The addition of p‐HBA increased the molecular packing and the limiting oxygen index and improved the thermal behavior of the synthesized polyesters. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Preparation and properties of 4,4′‐(hexafluoroisopropylidene) diphenol cured 2,2‐bis(4‐cyanatophenyl) propane

A novel easily curing system of 2,2‐bis(4‐cyanatophenyl) propane(BACY) was prepared by employing 4,4′‐(Hexafluoroisopropylidene) Diphenol (BPAF) as modifier. The curing efficiency of BPAF was evaluated by means of differential scanning calorimetry (DSC) and Fourier translation infrared spectroscopy analysis (FTIR). It was found that the exothermic peak temperature (T_p) was 168 °C when the content of BPAF/BACY was 15/85 by weight, while the temperature of BACY was 215 °C under the same conditions when trace of cobalt(III) acetylacetonate(CoAt(III)) was added. Besides, BPAF/BACY system owned outstanding properties including excellent curing characteristics, high shear strength, remarkable dielectric properties and high thermal stability in contrast to BACY, 4,4′‐(1‐methylethylidene) bisphenol(BPA)/BACY, and nonylphenol(NoP)/BACY systems. Moreover, the properties of cured BPAF/BACY modified by different proportions of BPAF were studied in detail. It was shown that moderate BPAF was conducive to most properties of polycyanurate, and the optimal proportion of BPAF/BACY was 15/85 by weight. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44518.     

Solution copolycondensation of isophthalic acid,terephthalic acid, 4,4′‐dihydroxydiphenylsulfone,and bisphenols with a tosyl chloride/dimethylformamide/pyridine condensing agent

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     

Synthesis and properties of TLCPs with 2,6‐naphthalene‐based mesogen,polymethylene spacer,and nonlinear 4,4′‐thiodiphenyl links

A series of new thermotropic main‐chain liquid crystalline copolyesters were prepared by polycondensation of 2,6‐naphthalenedicarbonyl chloride, 4,4′‐thiodiphenol, and α,ω‐alkanediols (n = 4–10) in diphenyl ether at 200°C. Thermal transition behaviors of these copolyesters were investigated by differential scanning calorimetry. Moreover, their thermal stabilities and mesomorphic textures were studied by thermogravimetric analysis and polarizing optical microscopy, respectively. Corresponding model compounds with terminal mesogenic units and central polymethylene spacers were also synthesized for comparison. Both copolymers and model compounds exhibit odd–even dependency of melting temperatures, transition enthalpy (ΔH_m), and entropy (ΔS_m) on the number of methylene units in the spacer. However, the odd–even effects in model compounds are much more distinctive. Nematic mesophases are the only texture observed in melts, except the model compounds with longer methylene units (n = 8, 10), in which smectic mesophases can be observed. The T_m values of the copolyesters (TDP/HD = 1/1) are between 233 and 259°C, depending on spacer length. The initial decomposition temperatures of the copolyesters are above 419°C under N₂ atmosphere. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1536–1546, 2002     

Properties of biodegradable copolyesters of succinic acid‐1,4‐butanediol/succinic acid‐1,4‐cyclohexanedimethanol

Although progress has been made in the study of biodegradable polyesters, little attention was given to aliphatic/alicyclic copolyesters. For this reason, we have undertaken systematic studies on the aliphatic/alicyclic copolyesters. As a first step in our research, we have presented the material characteristics (e.g., thermal and mechanical properties) and the biodegradability in different biological environments for a series of the aliphatic/alicyclic copolyesters that were synthesized by polycondensation of succinic acid, 1,4‐butanediol, and 1,4‐cyclohexanedimethanol. The chemical composition of the aliphatic/alicyclic copolyesters plays an important role in controlling the material characteristics and biodegradability. For the copolyesters with a mole fraction of succinic acid‐1,4‐cyclohexanedimethanol <0.3, an adjustment of the optimum between physical properties and biodegradability seems to be feasible. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 553–561, 1999     

Preparation and characterization of novel polyurethanes containing 4,4′‐{oxy‐1,4‐diphenyl bis(nitromethylidine)}diphenol schiff base diol

Four novel segmented polyurethanes (PUs) based on4,4′‐{oxy‐1,4‐diphenyl bis(nitromethylidine)}diphenol (ODBNMD) diol with different diisocyanates such as 4,4′‐diphenylmethane diisocyanate, toluene 2,4‐diisocyanate, isophorone diisocyanate, and hexamethylene diisocyanate have been prepared by solution method. The structures of ODBNMD and PUs have been confirmed by Fourier transform infrared (FTIR), nuclear magnetic resonance (¹H‐NMR and ¹³C‐NMR), UV‐visible, and fluorescence spectroscopies. The segmented PUs were further characterized by thermogravimetry (TGA), differential scanning calorimetry (DSC), and wide‐angle X‐ray diffraction. FTIR confirmed hydrogen bonding interactions, whereas TGA and DSC suggested that introduction of aromatic/phenyl ring in the main chain considerably increased the thermal stability. POLYM. ENG. SCI., 54:24–32, 2014. © 2013 Society of Plastics Engineers     

Preparation and characterization of new optically active poly(amide‐imide)s derived from N,N‐(4,4′‐Oxydiphthaloyl)‐bis‐(s)‐(+)‐valine diacid chloride and aromatic diamines

4,4′‐Oxydiphthalic anhydride (1) was reacted with (s)‐(+)‐valine (2) in acetic acid and the resulting imide‐acid 3 was obtained in high yield. This compound 3 was converted to diacid chloride 4 by reaction with excess amount of thionyl chloride. The polycondensation reaction of diacid chloride 4 with several aromatic diamines such as 4,4′‐sulfonyldianiline (5a), 4,4′‐diaminodiphenyl methane (5b), 4,4′‐diaminodiphenylether (5c), p‐phenylenediamine (5d), m‐phenylenediamine (5e), and 4,4′‐diaminobiphenyl (5f) was performed by two conventional methods: low temperature solution polycondensation and a short period reflux conditions. To compare conventional solution polycondensation reaction methods with microwave‐assisted polycondensation, the reactions were also carried out under microwave conditions in the presence of small amount of o‐cresol that acts as a primary microwave absorber. The reaction mixture was irradiated for 4 min with 100% of radiation power. Several new optically active poly(amide‐imide)s with inherent viscosity ranging from 0.26–0.44 dL/g were obtained with high yield. All of the above polymers were fully characterized by ¹H‐NMR, FTIR, elemental analyses, and specific rotation techniques. Some structural characterizations and physical properties of these new optically active poly (amide‐imide)s are reported. POLYM. ENG. SCI. 46:558–565, 2006. © 2006 Society of Plastics Engineers     

Copolycondensation of IPA/TPA,BPA, and 4,4′‐dihydroxydipehnylsulfone and 4,4′‐dicarboxydiphenylsulfone

Copolycondensations of IPA, TPA, bisphenol A (BPA), and several cimonomers were carried out to improve thermal properties, such as, the glass transition temperature (T_g) 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 T_gs 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 T_gs 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     

Microwave‐assisted and conventional polycondensation reaction of optically active N,N′‐(4,4′‐sulphonediphthaloyl)‐bis‐L‐leucine diacid chloride with aromatic diamines

3,3′,4,4′‐Diphenylsulfonetetracarboxylic dianhydride ( 1 ) was reacted with L‐leucine ( 2 ) in acetic acid and the resulting imide‐acid ( 3 ) was obtained in high yield. The diacid chloride ( 4 ) was prepared from diacid derivative ( 3 ) by reaction with thionyl chloride. The polycondensation reaction of diacid chloride ( 4 ) with several aromatic diamines such as 4,4′‐sulfonyldianiline ( 5a ), 4,4′‐diaminodiphenyl methane ( 5b ), 4,4′‐diaminodiphenylether ( 5c ), p‐phenylenediamine ( 5d ), m‐phenylenediamine ( 5e ), 2,4‐diaminotoluene ( 5f ), and 1,5‐diaminonaphthalene ( 5g ) was developed by using a domestic microwave oven in the presence of a small amount of a polar organic medium such as o‐cresol. The polymerization reactions were also performed under two conventional methods: low temperature solution polycondensation in the presence of trimethylsilyl chloride, and a short period reflux conditions. A series of optically active poly(amide‐imide)s with inherent viscosity of 0.25–0.42 dL/g were obtained with high yield. All of the above polymers were fully characterized by IR, elemental analyses, and specific rotation techniques. Some structural characterizations and physical properties of these optically active poly (amide‐imide) s are reported. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2992–3000, 2004     

Microwave‐assisted polycondensation of 4,4′‐(hexafluoroisopropylidene)‐N,N′‐bis(phthaloyl‐L‐leucine) diacid chloride with aromatic diols

A new facile and rapid polycondensation reaction of 4,4′‐(hexafluoroisopropylidene)‐N,N′‐bis(phthaloyl‐L ‐leucine) diacid chloride (1) with several aromatic diols such as phenol phthalein (2a), bis phenol‐A (2b), 4,4′‐hydroquinone (2c), 1,4‐dihydroxyanthraquinone (2d), 1,8‐dihydroxyanthraquinone (2e), 1,5‐dihydroxy naphthalene (2f), dihydroxy biphenyl (2g), and 2,4‐dihydroxyacetophenone (2h) was performed by using a domestic microwave oven in the presence of a small amount of a polar organic medium such as o‐cresol. The polymerization reactions proceeded rapidly, compared with the conventional solution polycondensation, and was completed within 10 min, producing a series of optically active poly(ester‐imide)s with quantitative yield and high inherent viscosity of 0.50–1.12 dL/g. All of the above polymers were fully characterized by IR, elemental analyses, and specific rotation. Some structural characterization and physical properties of this optically active poly(ester‐imide)s are reported. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 3003–3009, 2000     

Copolyesters of hydroxyphenylalkanoic acids: synthesis and thermal properties of poly{(4‐oxybenzoate)‐co‐[8‐(3‐oxyphenyl)octanoate]} and poly{(3‐bromo‐4‐oxybenzoate)‐co‐[8‐(3‐oxyphenyl)octanoate]}

Copolyesters of 8‐(3‐hydroxyphenyl)octanoic acid (HPOA), a monomer with kink and flexible segment derived from cardanol, and 4‐hydroxybenzoic acid (HBA) or its brominated derivative, 3‐bromo‐4‐hydroxybenzoic acid (BrHBA), were synthesized by acidolysis melt polycondensation of the in situ generated acetoxyderivative in the presence of magnesium acetate as catalyst by a one‐pot method and characterized. The formation of the copolyester was confirmed by elemental analysis, FTIR and ¹H NMR spectroscopy. These polymers were highly insoluble in most solvents except highly polar solvents, such as trifluoroacetic acid. The inherent viscosities of the soluble polymers were in the range of 0.8–1.1 dlg^?1. The thermal and phase behaviour of the copolyesters were studied by DSC and polarized light microscopy. Poly{(4‐oxybenzoate)‐co‐[8‐(3‐oxyphenyl)octanoate]} with 50 mole% of HPOA showed a birefringent melt with opalescence and a worm‐like texture of a nematic phase. The effect of bromine substitution in the analogue poly{(3‐bromo‐4‐oxybenzoate)‐co‐[8‐(3‐oxyphenyl)octanoate]} was evident when it showed a lower transition with minimum 45% Br‐HBA at 225 °C showing enhanced melt processability. These copolymers, with hydrolytically degradable aliphatic carbonyl group and better crystallinity compared to poly(hydroxyalkanoate)s, are interesting in possible biomedical applications. © 2002 Society of Chemical Industry     

Synthesis, 1H‐NMR characterization,and biodegradation behavior of aliphatic–aromatic random copolyester

Aliphatic‐aromatic copolyesters of poly(butylene adipate‐co‐butylene terephthalate) have been synthesized by polycondensation. Molecular weights and thermal properties have been measured. The four samples of copolyesters, with aromatic contents, varying from 40 to 60 mol %, were investigated by ¹H‐NMR spectroscopy to determine copolymers composition and microstructure. For all samples, the biodegradation experiment was carried out in compost, to study copolyesters degradation behavior. Using ¹H‐NMR, we noticed that the average sequence length and content of the aliphatic unit decrease and those of the aromatic unit increase. The molecular weights of the samples distinctly drop after composting. In all degraded samples, the trace of growing microorganisms was found on their surfaces by scanning electron microscopy. In combination with the results, the degradation behavior has been studied in the middle stage of copolyester degradation. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2643–2649, 2007     

Semiflexible random thermotropic copolymers from 8‐(3‐hydroxy phenyl) octanoic acid and 3‐chloro‐4‐hydroxy benzoic acid/3,5‐dibromo‐4‐hydroxy benzoic acid

Two series of semiflexible random thermotropic copolymers containing 8‐(3‐hydroxy phenyl) octanoic acid (HPOA) with either 3‐chloro‐4‐hydroxy benzoic acid or 3,5‐dibromo‐4‐hydroxy benzoic acid were prepared by melt polycondensation techniques. The copolyesters were characterized with Fourier transform infrared spectroscopy, dilute solution viscometry, hot‐stage polarized light microscopy, differential scanning calorimetry, thermogravimetric analysis, and wide‐angle X‐ray diffraction. Studies revealed that the amount of HPOA as a disruptor incorporated into the backbone of substituted 4‐hydroxy benzoic acids had a detrimental effect on the liquid‐crystalline behavior. Mesophase‐transition temperatures were observed between 210 and 250°C, and the optical textures were of typical nematic phases. The degree of crystallinity decreased with an increase in the HPOA content. The thermal stability of the copolymers was in the range of 310–370°C. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Synthesis and properties of poly(trimethylene terephthalate‐co‐2‐methyl‐ethylene terephthalate) random copolyesters

Poly(trimethylene terephthalate‐co‐2‐methyl‐ ethylene terephthalate) random copolymers of various compositions were synthesized via traditional two‐step polycondensation by incorporating of 1,2‐propanediol. The molar composition of trimethylene terephthalate and 2‐methyl‐ethylene terephthalate units and chemical structure were confirmed by means of ¹H‐NMR and Fourier transform infrared. The thermal properties of the copolyesters were evaluated by DSC and TGA. As far as the thermal properties is concerned, the main effect of incorporation of 1,2‐propanediol was a lowering in the melting temperature, and an increment of glass transition temperature compared to homopolymer PTT. Due to the effect of the lateral methyl groups in the polymeric chain, the thermal stability is slightly decreased as the amount of the MET units is increased. Furthermore, the crystals of PTT/MET copolyesters were observed by hot‐stage optical polarizing microscopy at the indicated crystallization temperatures. As expected, the incorporation of MET units in the polymer chain of PTT was found to decrease the dimension of the crystals. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Functional polyesters and copolyesters based on the 4,4′-dihydroxy-α-methylstilbene

Liquid crystalline (LC) thermotropic main-chain polyesters and copolyesters based on 4,4′-dihydroxy-α-methylstilbene (mesogen) and azelaoyl chloride (flexible spacer) and 10,12-docosadiynedioyl chloride [ultraviolet (UV)-crosslinkable moiety] were synthesized by interfacial polymerization. Improvement of molecular weight was achieved by the modification of interfacial polymerization. Molecular weights of the LC polymers ranged from 13,000 to 56,500 g/mol⁻¹, depending on composition of the LC polymers. Mesomorphic properties of these polymers were studied, and phase diagrams were established. Polymers showed nematic and smectic mesophases, depending on the flexible spacer composition. UV-crosslinking of the LC polymers containing UV-sensitive diacetylenic groups was attempted, and crosslinked LC polymer films were obtained. Mechanical properties of LC polymer films were also studied with a dynamic mechanical analyzer. The storage moduli of the polymer films, depending on the molecular weight of the polymers, increased by the UV-crosslinking. Higher molecular weights and crosslinking were favorable for the higher storage moduli of the films. The effect of orientation on the mechanical properties was also studied, and it was found that orientation induced the increase of the moduli of the films. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 387–393, 1998