A study of the thermal cure of a phenylethynyl-terminated imide model compound and a phenylethynyl-terminated imide oligomer (PETI-5)

The kinetic mechanism of the thermal cure of a phenylethynyl-terminated imide model compound, 3,4′-bis[(4-phenylethynyl)phthalimido]diphenyl ether (PEPA-3,4′-ODA) and a phenylethynyl-terminated imide oligomer PETI-5 (MW 5000 g/mol) was studied. FTIR was used to follow the cure of the model compound, while thermal analyses (DSC) was used to follow the cure of the PETI-5 oligomer. The changes in IR absorbance of phenylethynyl triple bonds at 2214 cm⁻¹ of PEPA-3,4′-ODA as a function of cure time were detected at 318, 336, 355, and 373°C, respectively. The changes in the glass transition temperature, T_g, of PETI-5 as a function of time were measured at 350, 360, 370, 380, and 390°C, respectively. The DiBenedetto equation was applied to define the relative extent of cure, x, of the PETI-5 oligomer by T_g. For the model compound, the reaction followed first order kinetics, yielding an activation energy of 40.7 kcal/mol as determined by infrared spectroscopy. For PETI-5, the reaction followed 1.5th order, yielding an activation energy of 33.8 kcal/mol for the whole cure reaction, as determined by T_g using the DiBenedetto method. However, the cure process of PETI-5 just below 90% by this method followed first-order kinetics yielding an activation energy of 37.2 kcal/mol. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36 : 461–470, 1998     

Development of novel cardo‐containing phenylethynyl‐terminated polyimide with high thermal properties

A phenylethynyl‐terminated reactive diluent [Card‐4‐phenylethynylphthalic anhydride (PEPA)], which contained fluorenyl cardo structures, was successfully synthesized and used as a modifier for flexible phenylethynyl‐terminated imide oligomer (PEI‐PEPA). The chemical structure, crosslink characterization, molecular weights, and thermal properties of the products were characterized. The imide systems with addition of 10, 20, 30, and 40 wt% Card‐PEPA to PEI‐PEPA (PEI‐PEPA‐Card) and their cured resin systems were prepared. The thermal curing behaviors of imide systems at different heating rates were analyzed by using differential scanning calorimetry. Thermal properties such as glass transition temperature (T_g) and char yield at 800°C of the resultant resin systems were studied by differential scanning calorimetry, dynamic mechanical analysis, and thermogravimetric analysis. The rheological properties were also investigated using a dynamic rheometry. These properties were found to be outstanding compared with pure PEI‐PEPA. The uncured imide systems exhibited lower T_g and lower isothermal viscosity with addition of Card‐PEPA. Furthermore, the T_g and char yield of the cured resin systems increased with addition of Card‐PEPA. The cured resin systems containing 40 wt% Card‐PEPA exhibited the highest T_g of 359°C and char yield at 800°C of 66.5%. Copyright © 2016 John Wiley & Sons, Ltd.     

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.     

Curing chemistry of phenylethynyl‐terminated imide oligomers: Synthesis of 13C‐labeled oligomers and solid‐state NMR studies

4‐(Phenylethynyl‐α,β‐¹³C)phthalic anhydride (PEPA) and ¹³C‐labeled phenylethynyl‐terminated imide (PETI) oligomers were synthesized, and solid‐state ¹³C nuclear magnetic resonance (NMR) spectroscopy was used to determine the structure of cured oligomers. Solid‐state ¹³C NMR spectra were collected before and after thermal curing. Using solid‐state ¹³C NMR difference spectroscopy, several cure products were identified. The observed ¹³C NMR resonances were assigned to four different classes of cure products: aromatics, products from backbone addition (substituted stilbenes and tetraphenylethanes), polyenes, and cyclobutadiene cyclodimers. The effects of postcuring and oligomer chain length on the structure of the cured resins were examined. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3486–3497, 2000     

Synthesis and thermal behavior of new poly(ethylene terephthalate‐imide)s

Copoly(ethylene terephthalate‐imide)s (PETIs) were synthesized by the melt copolycondensation of bis(2‐hydroxyethyl)terephthalate with a new imide monomer, N,N′‐bis[p‐(2‐hydroxyethoxycarbonyl)phenyl]‐biphenyl‐3,3′,4,4′‐tetracarboxydiimide (BHEI). The copolymers were characterized by intrinsic viscosity, Fourier transform infrared, ¹H NMR, differential scanning calorimetry, and thermogravimetric analysis techniques. Although their crystallinities decreased as the content of BHEI units increased, the glass‐transition temperatures (T_g) increased significantly. When 5 or 10 mol % BHEI units were incorporated into poly(ethylene terephthalate), T_g increased by 10 or 24 °C, respectively. The thermal stabilities of PETI copolymers were about the same as the thermal stability of PET, whereas the weight loss of PETIs decreased as the content of BHEI units increased. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 408–415, 2001     

3‐Phenylethynyl phthalimide end‐capped imide oligomers and the cured polymers

In the past decades, 4‐phenylethynyl phthalic anhydride (4‐PEPA) has been the most important endcapper used for thermoset polyimide. As the isomer of4‐PEPA, 3‐phenylethynyl phthalic anhydride (3‐PEPA) has attracted our interest. In this article, 3‐PEPA was synthesized and a comparative study with 4‐PEPA on curing temperature, curing rate, thermal and mechanical properties of oligomers and cured polymers was presented. The new phenylethynyl endcapped model compound, N‐phenyl‐3‐phenylethynyl phthalimide, was synthesized and characterized. The molecular structure of model compound was determined via single‐crystal X‐ray diffraction and the thermal curing process was investigated by Fourier transform infrared. Differential scanning calorimetry clearly showed that the model compound from 3‐PEPA had about 20 °C higher curing onset and peak temperature than the 4‐PEPA analog. This result was further proved by the dynamic rheological analysis that the temperature of minimum viscosity for oligomers end‐capped with 3‐PEPA was above 20 °C higher than that of the corresponding 4‐PEPA endcapped oligomers with the same calculated number average molecular weight. The cured polymer from 3‐PEPA displayed slightly higher thermal oxidative stability than those from 4‐PEPA by thermogravimetric analysis. The thermal curing kinetics of 3‐PEPA endcapped oligomer (OI‐5) and 4‐PEPA endcapped oligomer (OI‐6) fitted a first‐order rate law quite well and revealed a similar rate acceleration trend. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4227–4235, 2008     

Preparation and properties of polybenzoxazine/poly(imide‐siloxane) alloys: In situ ring‐opening polymerization of benzoxazine in the presence of soluble poly(imide‐siloxane)s

Benzoxazine monomer (Ba) was blended with soluble poly(imide‐siloxane)s in various weight ratios. The soluble poly(imide‐siloxane)s with and without pendent phenolic groups were prepared from the reaction of 2,2′‐bis(3,4‐dicarboxylphenyl)hexafluoropropane dianhydride with α,ω‐bis(aminopropyl)dimethylsiloxane oligomer (PDMS; molecular weight = 5000) and 3,3′‐dihydroxybenzidine (with OH group) or 4,4′‐diaminodiphenyl ether (without OH group). The onset and maximum of the exotherm due to the ring‐opening polymerization for the pristine Ba appeared on differential scanning calorimetry curves around 200 and 240 °C, respectively. In the presence of poly(imide‐siloxane)s, the exothermic temperatures were lowered: the onset to 130–140 °C and the maximum to 210–220 °C. The exotherm due to the benzoxazine polymerization disappeared after curing at 240 °C for 1 h. Viscoelastic measurements of the cured blends containing poly(imide‐siloxane) with OH functionality showed two glass‐transition temperatures (T_g's), at a low temperature around ?55 °C and at a high temperature around 250–300 °C, displaying phase separation between PDMS and the combined phase consisting of polyimide and polybenzoxazine (PBa) components due to the formation of AB‐crosslinked polymer. For the blends containing poly(imide‐siloxane) without OH functionalities, however, in addition to the T_g due to PDMS, two T_g's were observed in high‐temperature ranges, 230–260 and 300–350 °C, indicating further phase separation between the polyimide and PBa components due to the formation of semi‐interpenetrating networks. In both cases, T_g increased with increasing poly(imide‐siloxane) content. Tensile measurements showed that the toughness of PBa was enhanced by the addition of poly(imide‐siloxane). Thermogravimetric analysis showed that the thermal stability of PBa also was enhanced by the addition of poly(imide‐siloxane). © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2633–2641, 2001     

Synthesis and thermal behavior of phenylethynyl‐terminated linear and hyperbranched polyphenylquinoxalines

A phenylquinoxaline (PQ) AB monomer mixture was treated with monofunctional and difunctional end‐capping agents and with and without a coupling agent to afford phenylethynyl‐terminated linear PQ oligomers. The resulting PQ oligomers were soluble in common organic solvents and had intrinsic viscosities (IVs) of 0.21–0.30 dL/g. The glass‐transition temperature (T_g) of the diphenylethynyl‐end‐capped PQ oligomer on both sides increased the most, from 215 °C (before curing) to 251 °C (after curing). The PQ AB₂ monomer, which acted as both a coupling agent and a monomer for the hyperbranched polymer, was treated with an AB monomer and end‐capping agents to afford phenylethynyl‐terminated hyperbranched polyphenylquinoxalines (PPQs). They were also soluble in common organic solvents, had IVs of 1.00–1.65 dL/g and T_g's of 251–253 °C, and underwent exothermic cure with maxima around 412–442 °C. The T_g's of the cured hyperbranched PPQs ranged from 258 to 261 °C, depending on the number of phenylethynyl groups on the surface. After further curing, they displayed a T_g of 316 °C in one sample and turned into a fully crosslinked network. The dynamic melt viscosities of a linear oligomer (IV = 0.21 dL/g), a hyperbranched sample (IV = 1.00 dL/g), and a linear reference PPQ (IV = 1.29 dL/g) were compared with respect to the processing temperature. The PQ oligomer and hyperbranched PPQ had low melt viscosities. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 6318–6330, 2004     

Novel method for preparation of poly(benzoxazinone‐imide)

A novel method was developed to prepare poly(benzoxazinone‐imide) by the dealcoholization of poly(amide‐imide), having pendent ethoxycarbonyl groups, which was prepared from poly(amide acid). The poly(amide acid) was prepared from the reaction of pyromellitic dianhydride and 4,4′‐diamino‐6‐ethoxycarbonyl benzanilide. The curing behavior of the poly(amide acid) was monitored by DSC, which indicated the presence of two broad endotherms, one with maximum at 153 °C due to imide‐ring formation and the other with maximum at 359 °C due to benzoxazinone‐ring formation. The poly(amide acid) was thermally treated at 300 °C/1 h to get poly(amide‐imide) with pendent ester groups, then at 350 °C/2 h to convert into poly(benzoxazinone‐imide) by dealcoholization. Viscoelastic measurements of the poly(amide‐imide) showed that the storage modulus dropped at about 280 °C with glass‐transition temperature (T_g ) at about 340 °C. The storage modulus of poly(benzoxazinone‐imide), however, was almost constant up to 400 °C and no T_g was detected below 400 °C. Also, the tensile modulus and tensile strength of the poly(benzoxazinone‐imide) was much higher than that of the poly(amide‐imide). The 5% decomposition of poly(benzoxazinone‐imide) film was at 535 °C, which reflects its excellent thermal stability. Also, poly(benzoxazinone‐imide) showed more hydrolytic stability against alkali in comparison to polyimides. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1647–1655, 2000     

Design and synthesis of a tribranched phenylethynyl‐terminated aryl ether compound and its use as a reactive diluent for PETI‐5

In this study, a tribranched, phenylethynyl‐terminated aryl ether compound (Tri‐PE‐PAEK) was synthesized. This novel star‐shaped compound exhibits a good combination of properties, such as a low melting temperature (252 °C) and good solubility in aprotic solvents, as well as a low melt viscosity (0.1 P at 280 °C). All these advantages make it a good candidate material for modern processing techniques such as resin infusion and resin transfer molding, which are the most favorable methodologies for current economical manufacturing of polymer matrix/carbon fiber composites. Furthermore, after undergoing thermal curing to yield a network at 370 °C for 1 h, a cured sample exhibited an unexpectedly higher glass transition temperature (370 °C), storage modulus retention above the glass transition temperature, and good thermal stability. In addition, this compound can be used as a reactive diluent for phenylethynyl‐terminated imide oligomer, which has the molecular weight of 5000 g/mol (PETI‐5) to reduce its viscosity and lower the minimum temperature of the minimum viscosity. Meanwhile, the toughness of a cured blended resin can be greatly increased with the addition of just 10% Tri‐PE‐PAEK to PETI‐5. Further loading levels of Tri‐PE‐PAEK in the blending would lead to a higher storage modulus and a higher mechanical strength without compromising the thermal stability. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4844–4854, 2007     

Thermally stable and organosoluble binaphthylene‐based poly(urea‐ether‐imide)s: one‐pot preparation and characterization

A new family of wholly aromatic poly(urea‐ether‐imide)s ( 4a–4f ) possessing binaphthylene‐twisted rings was prepared by diphenyl azidophosphate (DPAP)‐activated one‐pot polyaddition reaction of a preformed imide heterocyclic ring‐containing dicarboxylic acid, 2,2′‐bis(4‐trimellitimidophenoxy)‐ 1,1′‐binaphthyl ( 1 ) with various kinds of aromatic diamines ( 3a–3f ). At first, with due attention to structural similarity and to compare the characterization data, a model compound 2 was synthesized by the reaction of diimide‐dicarboxylic acid 1 with two mole equivalents of aniline. In this direct method, the polymers were prepared by polyaddition reactions of the in situ‐formed diisocyanate with the aromatic diamines. Molecular weights of the poly(urea‐ether‐imide)s obtained were evaluated viscometrically, and the inherent viscosities (η_inh) measured were in the range 0.10– 0.25 dl/g. All of the polymers were characterized by FT‐IR spectroscopic method and elemental analysis. All of the resulting polymers exhibited an excellent solubility in common polar solvents such as N‐methyl‐2‐pyrrolidone (NMP), dimethyl sulfoxide (DMSO), N,N‐dimethylformamide (DMF), and N,N‐dimethylacetamide (DMAc). Crystallinity of the resulted polymers was evaluated by wide‐angle X‐ray diffraction (WXRD) method, and they exhibited nearly a non‐crystalline nature as evidenced by their diffractograms. The glass transition temperatures (T_g) of the polymers determined by differential scanning calorimetry (DSC) thermograms were in the range of 274–302°C. The temperatures at 10% weight loss (T_d10%) from their thermogravimetric analysis (TGA/DTG) curves were found to be in the range of 389–414°C in nitrogen atmosphere. Copyright © 2008 John Wiley & Sons, Ltd.     

Novel ortho‐linked fluorinated poly(ether‐imide)s based on 2,2′‐substituted 1,1′‐binaphthyl units

In this research, a new fluorinated diamine based on 2,2′‐substituted 1,1′‐binaphthyl units, 2,2′‐bis(2‐amino‐4‐trifluoromethylphenoxy)‐1,1′‐binaphthyl (AFPBN) was synthesized and then used to prepare the corresponding ortho‐linked poly(ether‐imide)s via chemical polyimidization with several aromatic carboxylic dianhydrides. The resulting poly(ether‐imide)s were fully characterized by FT‐IR, NMR, viscosity measurements, gel‐permeation chromatography, UV–vis, X‐ray diffraction, organo‐solubility, thermogravimetric analysis (TGA), and differential scanning calorimetry. Probing optical behavior of the colorless films prepared from these poly(ether‐imide)s demonstrated that they possess a high degree of optical transparency, and UV–visible absorption cut‐off wavelength values were found to be in the range of 404–471 nm. The resulting polymers exhibited excellent organo‐solubility in polar solvents such as dimethylformamide, dimethyl sulfoxide, pyridine, and even tetrahydrofuran. To investigate the heat stability of the samples, their thermograms obtained from TGA were plotted, and for example, it is found that the 10% weight loss temperature of representative polymer AFPBN/3,3′,4,4′‐benzophenonetetracarboxylic dianhydride occurred at 532°C in nitrogen. These poly(ether‐imide)s had glass‐transition temperatures (T_g's) up to 280°C. Two previously prepared analogues of AFPBN, i.e. nonfluorinated diamine DAM1 and para‐linked fluorinated diamine DAM2 used to prepare the corresponding poly(ether‐imide)s, were also considered to compare the results obtained. Copyright © 2012 John Wiley & Sons, Ltd.     

Poly(ethylene terephthalate) reinforced by N,N′‐diphenyl biphenyl‐3,3′,4,4′‐tetracarboxydiimide moieties

Starting with 3,3′,4,4′‐biphenyltetracarboxylic dianhydride and methyl aminobenzoate, we synthesized a novel rodlike imide‐containing monomer, N,N′‐bis[p‐(methoxy carbonyl) phenyl]‐biphenyl‐3,3′,4,4′‐tetracarboxydiimide (BMBI). The polycondensation of BMBI with dimethyl terephthalate and ethylene glycol yielded a series of copoly(ester imide)s based on the BMBI‐modified poly(ethylene terephthalate) (PET) backbone. Compared with PET, these BMBI‐modified polyesters had higher glass‐transition temperatures and higher stiffness and strength. In particular, the poly(ethylene terephthalate imide) PETI‐5, which contained 5 mol % of the imide moieties, had a glass‐transition temperature of 89.9 °C (11 °C higher than the glass‐transition temperature of PET), a tensile modulus of 869.4 MPa (20.2 % higher than that of PET), and a tensile strength of 80.8 MPa (38.8 % higher than that of PET). Therefore, a significant reinforcing effect was observed in these imide‐modified polyesters, and a new approach to higher property polyesters was suggested. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 852–863, 2002; DOI 10.1002/pola.10169     

Phosphinated phenols from acid‐fragmentation of bisphenols and their unsymmetrical diamine derivatives for copolyimides

Four novel diamines (9–12) were prepared by a two‐step procedure from phosphinated phenols (1–4) that were prepared from acid‐fragmentation of four bisphenols, including bisphenol A, 4,4′‐isopropylidenebis(2,6‐dimethylphenol), cis(4‐hydroxyphenyl)cyclohexane, and 9,9′‐bis(4‐hydroxyphenyl)fluorene, followed by nucleophilic addition of 9,10‐dihydro‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO). Copolyimides based on (9–12) /4,4′‐diaminodiphenyl ether (ODA)/dianhydride were prepared. The structure‐property relationship on the copolyimides was discussed. Due to the structural similarity, (9) /ODA‐based copolyimides were compared with (10) /ODA‐based copolyimides, while (11) /ODA‐based copolyimides were compared with (12) /ODA‐based copolyimides. The dimethyl substitutents cause (10) /ODA‐based copolyimides to display higher T_g, modulus, dimensional stability, contact angle, and better solubility than (9) /ODA‐based copolyimides. (12) /ODA‐based copolyimides that exhibit fluorene moieties display higher T_g and thermal stability, but a lower contact angle and poorer solubility than (11) /ODA‐based copolyimides that exhibit cyclohexane moieties. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 390–400     

Poly(ester imide)s possessing low coefficients of thermal expansion and low water absorption (IV): Effects of ester‐linked tetracarboxylic dianhydrides with longitudinally extended structures

A series of poly(ester imide)s (PEsIs) were prepared using longitudinally extended structures of ester‐linked tetracarboxylic dianhydrides with different numbers of aromatic rings (N_Ar = 4‐6). In the PEsIs obtained using p‐phenylenediamine (p‐PDA), a clear trend was observed: the water absorption (W_A) decreased with increasing N_Ar. In contrast, no clear decrease in the T_g with increasing N_Ar was observed for the PEsIs obtained using 4,4′‐oxydianiline (4,4′‐ODA). The PEsIs obtained using a methyl‐substituted tetracarboxylic dianhydride (N_Ar = 5) showed more suppressed W_A and higher elongation at break (ε_b) values than those of the nonsubstituted counterparts. The former result is probably closely related to the enhanced crystallinity. However, methyl substitution caused an appreciable reduction in the thermal stability. Thus, the methyl‐substituted PEsIs did not meet the V‐0 standard in the UL‐94V test, unlike the substituent‐free counterparts. The PEsI copolymer obtained using the substituent‐free tetracarboxylic dianhydride (N_Ar = 6) with p‐PDA (75 mol%) and 4,4′‐ODA (25 mol%) had excellent combined properties, ie, a very high T_g (361°C), an ultralow coefficient of thermal expansion (2.2 ppm K^?1), an extremely low coefficient of hygroscopic expansion (3.3 ppm/RH%), moderate film ductility (ε_b^max = 23%), a moderate dielectric constant (3.22), and a low tan δ (2.76 × 10^?3) at 10 GHz in 50% relative humidity. Thus, this PEsI is a promising novel dielectric substrate material for use in the next generation of high‐performance flexible printed circuit boards.     

New poly(amide–imide)s syntheses. XXIII. Synthesis and properties of poly(amide–imide)s derived from 4,4′‐[1,4‐phenylenebis(isopropylidene‐1,4‐phenyleneoxy)]dianiline and various bis(trimellitimide)s

A series of poly(amide–imide)s III_a–m containing flexible isopropylidene and ether groups in the backbone were synthesized by the direct polycondensation of 4,4′‐[1,4‐phenylenebis(isopropylidene‐1,4‐phenyleneoxy)]dianiline (PIDA) with various bis(trimellitimide)s II_a–m in N‐methyl‐2‐pyrrolidone (NMP) using triphenyl phosphite and pyridine as condensing agents. The resulting poly(amide–imide)s had inherent viscosities in the range of 0.80–1.36 dL/g. Except for those from the bis(trimellitimide)s of p‐phenylenediamine and benzidine, all the polymers could be cast from DMAc into transparent and tough films. They exhibited excellent solubility in polar solvents. The 10% weight loss temperatures of the polymers in air and in nitrogen were all above 495°C, and their T_g values were in the range of 201–252°C. Some properties of poly(amide–imide)s III were compared with those of the corresponding poly(amide–imide)s V prepared from the bis(trimellitimide) of diamine PIDA and various aromatic diamines. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 69–76, 1999     

Improvement of thermoplasticity for s‐BPDA/PDA by copolymerization and blend with novel asymmetric BPDA‐based polyimides

Asymmetric biphenyl type polyimides (PI) derived from 2,3,3′,4′‐biphenyltetracarboxylic dianhydride (a‐BPDA) and p‐phenylenediamine (PDA) or 4,4′‐oxydianiline (ODA) show higher T_gs, and much better thermoplasticity than the corresponding isomeric PIs from symmetric 3,3′,4,4′‐biphenyltetracarboxylic dianhydride (s‐BPDA). In addition, a‐BPDA‐derived PIs are completely amorphous owing to their bent chain structures and highly distorted conformations, whereas the PIs from s‐BPDA are semicrystalline. a‐BPDA‐derived PIs possessing these properties or the a‐BPDA monomer were used as a flexible blend component or a comonomer to improve the insufficient thermoplasticity of semirigid s‐BPDA/PDA homo polymer. The blends composed of s‐BPDA/PDA (80%) with a‐BPDA‐derived PIs (20%), as well as the s‐BPDA/PDA‐based copolymer containing 20% a‐BPDA, showed a certain extent of thermoplasticity above the T_gs without causing a decrease in T_g. In addition, these blends and copolymer provided comparatively low thermal expansion coefficient (ca. 18 ppm). The improved film properties for the blends are related to good blend miscibility. On the other hand, when s‐BPDA/ODA was used as a flexible matrix polymer instead of a‐BPDA‐derived PIs, the 80/20 blend film annealed at 400°C exhibited no prominent softening at the T_g. This result arises from annealing‐induced crystallization of the flexible s‐BPDA/ODA component. Thus, these results revealed that a‐BPDA‐derived PIs are promising candidates as matrix polymers for semirigid s‐BPDA/PDA for the present purpose. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2499–2511, 1999     

Synthesis and optical properties of novel soluble and optically transparent semifluorinated poly (ether imide)s

A fluorinated diamine monomer containing flexible ether linkage and bulky trifluoromethyl substituents, namely, bis(4‐amino‐2‐trifluoromethylphenyl) ether (a), is employed to react with nonfluorinated 1,4‐bis(3,4‐dicarboxyphenoxy) benzene dianhydride (3) and CF₃‐free 2,2‐bis[4‐(3,4‐dicarboxyphenoxy)phenyl] propane dianhydride (4), respectively, to prepare 2 novel soluble and optically transparent semi‐fluorinated poly (ether imide)s (PEIs; 3a and 4a). Compared with the corresponding PEIs based on nonfluorinated 4,4′‐diaminodiphenyl ether (b) and CF₃‐free pyromellitic dianhydride (5), the novel semifluorinated PEIs 3a and 4a not only display better solubility in some organic solvents and higher optical transparency with cutoff absorption wavelength (λ₀) below 370 nm but also maintain outstanding mechanical properties and thermal stability. 3a and 4a have tensile strength beyond 80 MPa and possess glass‐transition temperatures (T_g) beyond 210°C, coupled with the temperatures of 5% weight loss (T_5%) exceeding 500°C. It is also found that 3a and 4a exhibit contact angles against water beyond 110° and water absorptions below 0.8% together with dielectric constants less than 3.2.     

Thiol–ene polymerizations using imide‐based monomers

New diene and dithiol monomers, based on aromatic imides such as benzophenone‐3,3′,4,4′‐tetracarboxylic diimide were synthesized and used in thiol‐ene polymerizations which yield poly(imide‐co‐thioether)s. These linear polymers exhibit limited solubility in various organic solvents. The molecular weights of the polymers were found to decrease with increasing imide content. The glass transition temperature (T_g) of these polymers is dependent on imide content, with T_g values ranging from ?55 °C (with no imide) up to 13 °C (with 70% imide). These thermal property improvements are due to the H‐bonding and rigidity of the aromatic imide moieties. Thermal degradation, as studied by thermogravimetric analysis, was not significantly different to the nonimide containing thiol‐ene polymers made using trimethyloylpropane diallyl ether and 3,5‐dioxa‐1,8‐dithiooctane. It is expected that such monomers may lead to increased glass transition temperatures in other thiol‐ene polymer systems as these normally exhibit low glass transition temperatures. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4637–4642     

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.