Preparation and properties of imide‐containing elastic polymers from elastic polyureas and pyromellitic dianhydride

A new approach to obtain imide‐containing elastic polymers (IEPs) via elastic and high‐molecular‐weight polyureas, which were prepared from α‐(4‐aminobenzoyl)‐ω‐[(4‐aminobenzoyl)oxy]‐poly(oxytetramethylene) and the conventional diisocyanates such as tolylene‐2,4‐diisocyanate(2,4‐TDI), tolylene‐2,6‐diisocyanate(2,6‐TDI), and 4,4′‐diphenylmethanediisocyanate (MDI), was investigated. IEP solutions were prepared in high yield by the reaction of the polyureas with pyromellitic dianhydride in N‐methyl‐2‐pyrrolidone (NMP) at 165°C for 3.7–5.2 h. IEPs were obtained by the thermal treatment at 200°C for 4 h in vacuo after NMP was evaporated from the resulting IEP solutions. We assumed a mechanism of the reaction via N‐acylurea from the identification of imide linkage and amid acid group in IEP solutions. NMR and FTIR analyses confirmed that IEPs were segmented polymers composed of imide hard segment and poly(tetramethylene oxide) (PTMO) soft segment. The dynamic mechanical and thermal analyses indicated that the IEPs prepared from 2,6‐TDI and MDI showed a glass‐transition temperature (T_g ) at about −60°C, corresponding to T_g of PTMO segment, and suggested that microphase‐separation between the imide segment and the PTMO segment occured in them. TGA studies indicated the 10% weight‐loss temperatures (T₁₀) under air for IEPs were in the temperature range of 343–374°C. IEPs prepared from 2,6‐TDI and MDI showed excellent tensile properties and good solvent resistance. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 715–723, 2000     

Polyisobutylene‐based segmented polyureas. I. Synthesis of hydrolytically and oxidatively stable polyureas

Novel segmented polyurea elastomers containing soft polyisobutylene (PIB) segments were synthesized and characterized. The key ingredient, primary amine‐telechelic PIB oligomers (NH₂‐PIB‐NH₂) with number average molecular weights of 2500 and 6200 g/mol were synthesized. PIB‐based polyureas were prepared by using various aliphatic diisocyanates and diamine chain extenders with hard segment contents between 9.5 and 46.5% by weight. All copolymers displayed microphase morphologies as determined by dynamic mechanical analysis. Tensile strengths of nonchain‐extended and chain‐extended polyureas showed a linear dependence on the urea hard segment content. PIB‐based polyureas prepared with NH₂‐PIB‐NH₂ of M_n = 2500 g/mol, 4,4′‐methylendbis(cyclohexylisocyantate), and 1,6‐diaminohexane containing 45% hard segment exhibited 19.5 MPa tensile strength which rose to 23 MPa upon annealing at 150 °C for 12 h. With increasing hard segment content, elongation at break decreased from ～ 450% to a plateau of 110%. The hydrolytic and oxidative stability of PIB‐based polyureas were unprecedented. Although commercial “oxidatively resistant” thermoplastic polyurethanes degraded severely upon exposure to boiling water or concentrated nitric acid, the experimental polyureas survived without much degradation in properties. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 38–48, 2009     

Structure and thermal behaviors of poly(vinyl alcohol)/surfactant composites: Investigation of molecular interaction and mechanism

Poly(vinyl alcohol) (PVA) is a promising biocompatible polymer, whose applicability is limited by its narrow processing window. Here, we adopted a facile approach to broaden the processing windows of PVA based on phosphoric ester of poly(ethylene oxide) (10) nonylphenyl (NP‐10P). Thermal analysis shows that both the melting temperature (T_m) and the glass transition temperature (T_g) of PVA decrease noticeably as NP‐10P content increases, indicating good miscibility of NP‐10P with PVA. The thermal degradation kinetics suggests composites display excellent thermal stability compared with neat PVA. The pyrolysis mechanism of PVA before and after modification with NP‐10P varies from chain unzipping degradation followed by chain random scission to chain random scission. The processing window of PVA is broadened from 9°C to 98°C with low content NP‐10P (5 wt%). Moreover, the composites maintain significant mechanical performance and transparency. This work provides an environmentally friendly and economical method to improve the possibility of thermal melt processing for PVA.     

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     

Cure mechanism of novel bismaleimide resins based on fluorene cardo moiety and their thermal properties

In this paper, two novel bismaleimide resins based on 9, 9-bis[4-(4-maleimidophenoxy) phenyl] fluorene (PFBMI), 9, 9-bis[4-(4-maleimidophenoxy)-3-methylphenyl]fluorene (MFBMI), and 2, 2’-diallyl bisphenol A (DABPA) were prepared. Their curing mechanism and curing kinetic were carefully investigated by Differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). The thermal mechanical properties of the composites based on these BMI resins and the glass cloth were obtained by Dynamic mechanical analysis (DMA), displaying that the novel resins whose T_g were 296°C and 289°C had excellent thermal performance. In addition, Thermogravimetric analysis (TGA) results showed that both the cured PD and MD resins possessed good thermal stability, and their T_5% were all higher than 410°C.     

Segmented block copolyesters using click chemistry

Copper(I) catalyzed azide‐alkyne 1,3‐Huisgen cycloaddition reaction afforded the synthesis of triazole‐containing polyesters and segmented block copolyesters at moderate temperatures. Triazole‐containing homopolyesters exhibited significantly increased (～40 °C) glass transition temperatures (T_g) relative to high temperature, melt synthesis of polyesters with analogous structures. Quantitative synthesis of azido‐terminated poly(propylene glycol) (PPG) allowed for the preparation of segmented polyesters, which exhibited increased solubility and mechanical ductility relative to triazole‐containing homopolyesters. Differential scanning calorimetry demonstrated a soft segment (SS) T_g near ?60 °C for the segmented polyesters, consistent with microphase separation. Tensile testing revealed Young's moduli ranging from 7 to 133 MPa as a function of hard segment (HS) content, and stress at break values approached 10 MPa for 50 wt % HS segmented click polyesters. Dynamic mechanical analysis demonstrated an increased rubbery plateau modulus with increased HS content, and the T_g's of both the SS and HS did not vary with composition, confirming microphase separation. Atomic force microscopy also indicated microphase separated and semicrystalline morphologies for the segmented click polyesters. This is the first report detailing the preparation of segmented copolyesters using click chemistry for the formation of ductile membranes with excellent thermomechanical response. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Synthesis and properties of thermoplastic polyimides with ether and ketone moieties

A series of polyimides containing ether and ketone moieties were synthesized from 1,3‐bis(4‐fluorobenzoyl) benzene and several commercially available dianhydrides via a conventional two‐step polymerization. The inherent viscosities of Polyamide acids ranged from 0.46 to 0.73 dL/g. Thermal properties, mechanical properties, and thermalplasticity of the obtained polimide films were investigated by focusing on the chemical structures of their repeat units. These films were amorphous, flexible, and transparent. All films displayed low T_gs (184–225 °C) but also excellent thermal stability, the 5% weight loss temperature was up to 542 °C under nitrogen. The films showed outstanding mechanical properties with the modulus up to 3.0 GPa and the elongation at break in the range of 8–160%. The uniaxial stretching of PI‐a at high temperature was studied owing to its excellent flexibility. The PI‐a had an elongation at break up to 1600% at 245 °C and the uniaxially stretched film exhibited a much higher modulus (3.9 GPa) and strength (240 MPa) than undrawn film. The results indicated that PI‐a can potentially be used to prepare materials such as fiber, ultra‐thin film or ultra‐high modulus film. All the obtained films also demonstrated excellent thermoplasticity (drop of E′ at T_g > 10³) which made the polyimides more suitable for melt processing. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2878–2884, 2010     

Improvement of thermal and mechanical properties of poly(L‐lactic acid) with 4,4‐methylene diphenyl diisocyanate

In this study, the thermal and mechanical properties of biodegradable poly(L ‐lactic acid) (PLA) were improved by reacting with 4,4‐methylene diphenyl diisocyanate (MDI). The resulting PLA samples were characterized with Fourier transformation infrared spectrometer (FT‐IR). The glass transition (T_g) and decomposing (T_d) temperature of the resulting products were measured using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), respectively. The tensile properties were also measured with a tensile tester. The results show that when the molar ratio of ? NCO to ? OH was 2:1, the T_g value can be increased to 64°C from the original 55°C, and the tensile strength increased from 4.9 to 5.8 MPa. This demonstrated that by reacting PLA with MDI at an appropriate portion, both the thermal and mechanical performance of PLA can be increased. Copyright © 2006 John Wiley & Sons, Ltd.     

Chain extension of adipic acid and (or) succinic acid/butanediol polyesters with 2,2′‐(1,4‐phenylene)‐bis(2‐oxazoline) and adipoylbiscaprolactamate combined chain extenders

This paper provided an easy and flexible method to synthesize high molecular weight polyesters by polycondensation and chain extension. Low molecular weight polybutylene adipate, polybutylene succinate, and poly(butylene succinate‐co‐butylene adipate) (PBSA) were synthesized through melt condensation polymerization from adipic acid and/or succinic acid with butanediol. The prepolyesters obtained had different amount of ? COOH and ? OH terminal groups. Chain extension of them was carried out at 180–240°C using 2,2′‐(1,4‐phenylene)‐bis(2‐oxazoline) and adipoyl biscaprolactamate as combined chain extenders. The influencing factors of the chain extension were studied. At the optimal conditions, chain‐extended polybutylene adipate with M_n up to 39,100, polybutylene succinate with intrinsic viscosity of 0.99 dl/g, and PBSA with intrinsic viscosity from 0.73 to 0.81 dl/g were synthesized. The chain‐extended polyesters were characterized by IR spectrum, ¹H NMR spectrum, differential scanning calorimetry, thermogravimetric analysis (TGA), wide angle X‐ray scattering, and tensile test. The thermal analysis showed that chain extension often led to slight decrease of the regularity, the crystallinity, and the melting point. This deterioration of the properties is not harmful enough to impair their thermal properties and obstruct them from being used as biodegradable thermoplastics. The TGA showed that the chain‐extended polyesters were stable with initial decomposition temperature over 354.7°C. The tensile strength of the chain extended PBS and PBSAs with butylene adipate units less than 20 mol% was in the range of 18.95–31.22 MPa. Copyright © 2010 John Wiley & Sons, Ltd.     

Sulfonated liquid crystalline polyesters as resin matrix for single wall carbon nanotube and nanodiamond composites

The focus of this study is on incorporating pendant sulfonate groups along the backbone of a liquid crystalline polyester (LCPE) with the aim to improve the dispersion of single wall carbon nanotubes (SWNTs) and nanodiamonds (NDs). Two LCPE matrices, one sulfonated (LCPE‐S) and one nonsulfonated reference polymer (LCPE‐R), were successfully synthesized via a melt condensation method using aromatic and aliphatic AB, AA, and BB‐type monomers. Upon the introduction of SWNT and ND particles, the glass transition temperature (T_g) of the sulfonated LCPE increased from 21.5 °C to 41.0 °C and 41.9 °C, for SWNTs and NDs, respectively. When sulfonate groups were absent, a decrease in T_g was observed. The storage modulus (E′) followed a similar trend, i.e., E′ increased from 1.3 GPa to 5.2 GPa and 3.4 GPa, upon the addition of NDs and SWNTs. The LCPE‐S showed a lower thermal stability due to the loss of sulfonate groups, i.e. the 5% weight loss temperature (T) is ～280 °C for LCPE‐S vs. 333 °C for LCPE‐R. The decomposition temperature increased somewhat upon addition of the nanoparticles. The ability of dispersing carbon‐based nanostructures combined with an accessible melt processing window makes sulfonated LCPs attractive matrices towards preparing nanocomposites with improved thermal and mechanical properties. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011.     

Copolymerization of fluorene‐based main‐chain benzoxazine and their high performance thermosets

A series of fluorene‐based benzoxazine copolymers were synthesized from the mixture of 9,9‐bis(4‐hydroxyphenyl)fluorene and bisphenol A, and 4,4′‐diaminodiphenyloxide and paraformaldehyde. And the cured polybenzoxazine films derived from these copolymers were also obtained. Fourier transform infrared spectroscopy (FTIR) and hydrogen nuclear magnetic resonances confirmed the structure of these benzoxazines. Their molecular weight was estimated by gel permeation chromatography. The curing behavior of the precursors was monitored by FTIR and differential scanning calorimetry. Dynamic mechanical analysis and thermogravimetric analysis were performed to study the thermal properties of the cured polymers. The cured polybenzoxazines exhibit excellent heat resistance with glass transition temperatures (T_g) of 286–317°C, good thermal stability along with the values of 5% weight loss temperatures (T₅) over 340°C, and high char yield over 50% at 800°C. The mechanical properties of the cured polymers were also measured by bending tests. Copyright © 2015 John Wiley & Sons, Ltd.     

Biodegradable aromatic copolyesters made from bicyclic acetalized galactaric acid

Random poly(hexamethylene terephthalate‐co‐galactarate)s and poly(dodecamethylene terephthalate‐co‐galactarate)s copolyesters covering the whole range of compositions were obtained with weight‐average molecular weights of ～30,000–50,000 g mol^?1 by melt polycondensation. They were thermally stable above 300 °C, and displayed T_g in the +20 to ?20 °C range with values steadily decreasing with the content in galactarate units. All the copolyesters were semicrystalline with T_m between 50 and 150 °C and those made from dodecanediol were able to crystallize from the melt at a crystallization rate depending on composition. Copolyesters containing up to 50% of galactaric units retained the crystal structure of their respective polyterephthalate homopolyesters, whereas they adopted the structure of the respective polygalactarates when the content in Galx units reached 70%. Stress‐strain essays revealed decay in the mechanical parameters as the aromatic units were replaced by Galx. Incubation in aqueous buffer revealed that hydrolysis of the polyesters were largely enhanced by copolymerization and evidenced the capacity of the Galx unit for making aromatic polyesters susceptible to biodegradation. A detailed NMR analysis complemented by SEM observations indicated that hydrolysis took place by preferred splitting of galactarate ester bonds with releasing of alkanediol and Galx‐diacid. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Preparation,characterization, and properties of poly(thioether ether imide)s from isomeric bis(chlorophthalimide)s and 4,4′‐thiobisbenzenethiol

A series of isomeric poly(thioether ether imide)s (PTEIs) containing both thioether and ether linkages were prepared by nucleophilic substitution reaction of isomeric bis(chlorophthalimide)s with 4,4′‐thiobisbenzenethiol. The inherent viscosities of these polymers were in the range of 0.40–0.56 dL/g in m‐cresol at 30°C. The T_g values of PTEIs were 196–236°C; T_5% values reached up to 509–529°C in nitrogen and 508–534°C in air, which indicated this kind of polyimide possessed excellent thermal stability. The hydrolytic stability was arranged in the order: a > b > c > d > e, and improved with increasing the content of 3‐substituted phthalimide unit in the polymer backbone. Flexible films could be cast from the polymer solution with a solid content of 10%. The PTEI films exhibited good mechanical properties with tensile strengths of 90–104 MPa, elongations at break of 6.6–7.9%, and tensile moduli of 2.3–2.6 GPa. The minimum complex viscosity of PTEIs c was about 100 Pa·s at 310°C and the minimum melt viscosity of PTEIs (a–e) decreased with increasing the content of unsymmetrical 3,4′‐substituted phthalimide units. Copyright © 2014 John Wiley & Sons, Ltd.     

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     

Novel heterocyclic poly(pyridine‐imide)s with unsymmetric carbazole substituent and noncoplanar structure: High thermal,mechanical and optical transparency,electrochemical, and electrochromic properties

A diamine containing heterocyclic pyridine and unsymmetrical carbazole substituents, 4‐(9‐ethyl‐3‐carbazole)‐2,6‐bis(4‐aminophenyl)pyridine ( CBAPP ), was prepared for use in the synthesis of poly(pyridine‐imide)s PI‐1–8 by direct polycondensation with dianhydrides in N,N‐dimethylacetamide (DMAc). The poly(pyridine‐imide)s derived from the diamine are highly soluble in solvents such as N‐Methyl‐2‐pyrrolidone (NMP) and DMAc at room temperature. Noncoplanar polyimide (PI‐1) showed excellent solubility, high transparency, and high‐performance mechanical properties. These polymers had relatively high glass transition temperatures and exhibited good thermal stability in both nitrogen (T_d10 > 470 °C) and air (T_d10 > 450 °C). The PI‐3～5 cannot form flexible and tough films due to the unsymmetrical carbazole moiety, rigid structure, and polar–polar interaction. However, through copolymerization technique these polymers (PI‐6～8) could be enhanced through the solubility, mechanical, and thermal properties. The optical properties included a strong orange fluorescence (540 nm) after protonation with acid. When the HCl concentration was increased, a new absorption band at approximately 350 nm appeared, and the intensity of the fluorescent peak at 380 nm observed in the neutral polymer solution decreased, along with the appearance of the new fluorescent peak at 540 nm. The poly(pyridine‐imide)s presented here showed only slight fluorescence quenching in the presence of methanol. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 405–412     

Hydrolytic stability and high Tg of polyimides derived from the novel 4,9‐bis[4‐(3,4‐dicarboxyphenoxy)phenyl]‐diamantane dianhydride

This work reports the synthesis and characterization of diamantane‐based polyimides obtained from 4,9‐bis[4(3,4‐dicarboxyphenoxy)phenyl]diamantane dianhydride and various aromatic diamines. Interestingly, the diamantane‐based polyimides were very stable to hydrolysis. This novel polyimide exhibits a low dielectric constant (2.65–2.77), low moisture absorption (<0.67%), good solubility, high T_g and unusually high thermal stability. Dynamic mechanical analysis (DMA) reveals that the diamantane‐based polyimides have high T_g ranging from 281 to 379 °C. The high‐temperature β₁ subglass transition around 285 °C was observed in polyimide 6a derived from 2,2′‐bis(trifluoromethyl)benzidine. This class of novel diamantane‐based polyimide is very promising for electronic applications, because of its good mechanical properties, good thermal stability, low dielectric constant, excellent hydrolytic resistance, and low moisture absorption. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1673–1684, 2009     

Copolymerization of elemental sulfur with cyclic(arylene disulfide) oligomers

Copolymerization reactions between cyclic(arylene disulfide) oligomers were studied. The cyclic disulfide oligomers derived from 4,4′-isopropylidene bisbenzenethiol gave soluble polysulfanes via copolymerization with S₈. The copolymerization reactions were studied both in solution and melt by GPC and NMR. Solution copolymerization reactions can only form polysulfanes with up to three to four sulfur linkages; however, melt copolymerization reactions gave polysulfanes with up to seven sulfur linkages (average). The melt copolymerization reactions between cyclic disulfide oligomers derived from 4,4′-thiobis(benzenethiol) and S₈ were studied using DSC, TGA, and DMTA. With increasing contents of sulfur in the polysulfanes, T_gs, 5% weight losses by TGA, and tan δ decreased. With seven sulfur linkages in the polymer, it is a rubber with a T_g of 12°C, a 5% weight loss by TGA of 249°C, and tan δ of 44°C, respectively. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2961–2968, 1997     

Polyisobutylene‐based polyurethanes. IX. synthesis,characterization, and properties of polyisobutylene‐based poly(urethane‐ureas)

Polyisobutylene (PIB)‐based polyurethanes (PUs) exhibit unparalleled hydrolytic‐oxidative‐biologic stability and are melt processible, however, their mechanical (strength) properties are modest mainly due to insufficient H bonds. We posited and demonstrate that the ultimate properties of PIB‐PUs are enhanced, while their melt processibility is maintained, by the judicious introduction of urea linkages, i.e., strong bifurcated H bonds, in the chain. The incorporation of bifurcated H bonds in PIB‐PUs was achieved by using the conventional butane diol chain extender (CE) in combination with controlled amounts of amino alcohol as co‐chain extender (co‐CE). Polyurethanes containing both urethane and urea linkages are polyurethane‐ureas (PUU). Specifically, PIB‐PUUs prepared with PIB‐diol/MDI together with 80/20 mole % butane diol/amino butanol exhibited ～30 MPa tensile strength, ～550% elongation, ～80 Shore A hardness, and ～137 °C flow temperature. Other amino alcohols, i.e., amino ethanol, ‐propanol, and ‐hexanol, were less effective co‐CEs. ¹H‐NMR and FT‐IR spectroscopies indicate the presence of bifurcated H bonds in PIB‐PUUs prepared with CE/co‐CE combinations. Characterization by differential scanning calorimetry, thermogravimetric analysis, dynamic mechanical thermal analysis, and creep experiments also suggest bifurcated H bonds in PIB‐PUU. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2361–2369     

Synthesis and characterization of thermotropic liquid crystalline poly(ester imide)s

Two closely series of poly(ester imide)s had been synthesized by solution polycondensation of p‐phenylenebis(trimellitate) dianhydride with aliphatic diamines. The differential scanning calorimetry (DSC) traces of the most poly(ester imide)s exhibited two endotherms representing the solid state to anisotropic phase transition (T_m1) and the anisotropic to isotropic melt transition (T_m2), respectively. Observation under polarizing microscope and wide‐angle X‐ray diffraction (WAXD) measurements suggested that the anisotropic phase formed above the melting points (T_m1) had a smectic character. The thermogravimetric analyses (TGA) revealed that the thermal stabilities of the poly(ester imide)s were up to 350°C. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 211–218, 1999     

Thermal analysis of phenylethynyl end-capped fluorinated imide oligomer afr-pepa-4

Thermal analysis of phenylethynyl end-capped imide oligomer AFR-PEPA-4 was performed to characterize cure reaction, thermal stabilities and semicrystalline behavior of AFR-PEPA-4 oligomer and its cured polyimide. Cured AFR-PEPA-4 polyimide showed high T _gs up to 418°C. Both AFR-PEPA-4 oligomer and polyimide exhibit excellent thermal stabilities comparable to PETI-5 polyimides. AFR-PEPA-4 imide oligomer has a T _m of 330°C and exhibits spherulite crystalline morphology in the film. The crystallinity in AFR-PEPA-4 films could not be regenerated under any annealing conditions after the initial melt.