Synthesis and characterization of photo‐crosslinkable poly(amic acid ester)s with 2‐hydroxy‐4‐oxo‐hept‐5‐enyl side chain

Photosensitive poly(amic acid ester)s (PAEs) with 2‐hydroxy‐4‐oxo‐hept‐5‐enyl side group were simply synthesized from a non‐photosensitive polyamic acid (PAA), which was prepared from cyclobutane‐1,2,3,4‐tetracarboxylic dianhydride (CBDA) and 4,4′‐diaminodiphenyl ether (DDE) in N‐methyl‐2‐pyrrolidinone (NMP). 1‐oxiranyl‐pent‐3‐en‐2‐one was added to the poly(amic acid) solution to give the photosensitive PAEs by a ring opening esterification of the poly(amic acid). The esterification reaction was conducted with changing a reaction time and amounts of 1‐oxiranyl‐pent‐3‐en‐2‐one. The degree of esterification (DOE) increased with increasing esterification reaction time and amounts of 1‐oxiranyl‐pent‐3‐en‐2‐one. A photo‐lithography evaluation for the PAE‐D4 with the highest DOE was conducted in the presence of 1‐[4‐(phenylthio)phenyl]‐2‐(O‐benzoyloxime)‐1,2‐octanedione (PPBO) as a photoinitiator at a wavelength of 365 nm using a high‐pressure mercury lamp. The normalized film thicknesses for PAE‐D3 were measured with various post‐exposure baking (PEB) temperatures, which showed that the optimum PEB temperature was 120°C. The resolution of the resulting polyimide film cured at 250°C for 60 min was 25 µm. The initial decomposition temperature of the polyimide film was around 354°C and there was no weight loss at the temperature of 250–350°C. Copyright © 2009 John Wiley & Sons, Ltd.     

Synthesis of poly(2-cyclohexenone-4-yl methacrylate) and acidolysis of pendant protecting groups in the polymer

4-Acetoxy-2-cyclohexenone (ACH) and 2-cyclohexenone-4-yl methacrylate (CHM) were obtained from the condensation reaction of 4-bromo-2-cyclohexenone (BCH) with acetic acid and methacrylic acid using 1,8-diazabicyclo-[5,4,0]-7-undecene (DBU), respectively. Poly(2-cyclohexenone-4-yl methacrylate) ( P-1 ) containing acid-sensitive 2-cyclohexenone-4-yl group was prepared from the radical polymerization of CHM and the esterification of poly(methacrylic acid) with BCH using DBU. Furthermore, P-1 and CHM copolymers ( P-2 and P-3 ) were easily synthesized from the radical polymerization of methacrylic acid and comonomers in dimethylsulfoxide using 1 mol % of 2,2′-azobis (isobutyronitrile) followed by esterification of the resulting polymers with BCH using DBU by one-pot method. The deprotection reaction of ACH and P-1 was carried out in dichloromethane using an acid catalyst. The reaction proceeded smoothly in solution to give phenol and the corresponding carboxylic acid. Therefore, the 2-cyclohexenone-4-yl group is a useful protecting group for carboxylic acids, because the protection and deprotection reactions are very easy. In the case of polymer films, however, the acid was trapped by carbonyl group on the 2-cyclohexenone-4-yl group, and did not cause the deprotection reaction. © 1993 John Wiley & Sons, Inc.     

Photochemical addition reaction of a polymer-bearing pendant vinyl ether with various thiol compounds

Photochemical addition reaction of the pendant vinyl ether group in the polymer ( P-1 ), which was synthesized by the alternate ring-opening copolymerization of glycidyl vinyl ether with phthalic anhydride, with various thiol compounds such as benzenethiol, phenylmethanethiol, 2-mercaptoacetic acid, ethyl 2-mercaptoacetate, N-acetyl-L -cysteine (AcCys), and 1,4-phenylenedi(methylthiol) was carried out using benzophenone (BP) as the photosensitizer in the THF solution. Each reaction proceeded very smoothly to give the corresponding polymers with high conversion, although the degree of reaction of the pendant vinyl ether group in P-1 was affected by the molar ratio between the thiol compounds and the vinyl ether group, and the amounts of photosensitizer BP added. Furthermore, it was also found that optically active polymer containing pendant N-acetyl-L -cysteine residue was synthesized by the photochemical addition reaction of P-1 with AcCys. The reactions of P-1 with dithiol or bisazide compounds occurred effectively to give gel products in the film state, and it was found that the polymer film containing P-1 and those compounds can be applied as negative-type photoresists with high practical photosensitivity. © 1993 John Wiley & Sons, Inc.     

Synthesis of polymers in aqueous solutions: Esterification reaction of poly(methacrylic acid) with alkyl halides using DBU in aqueous solutions

A convenient esterification reaction of poly(methacrylic acid) (PMAA) with certain alkyl halides was performed using 1,8-diazabicyclo-[5.4.0]-7-undecene (DBU) as a base in aqueous solution or in water. The esterification reaction of PMAA with propargyl bromide (PB) proceeded very smoothly and quantitatively at 30°C to give corresponding poly(propargyl methacrylate), although the rate of the reaction decreased with increasing water. The reaction of PMAA with benzyl bromide, o-nitrobenzyl bromide, and p-nitrobenzyl bromide gave corresponding poly(methacrylic ester) using DBU under suitable reaction conditions in water. The esterification reactions of PMAA with PB were carried out using certain organic bases such as triethylamine, 4(N,N-dimethylamino)pyridine and pyridine. Inorganic bases such as sodium carbonate, sodium hydroxide, potassium carbonate, and potassium hydroxide were also tried under the same conditions as with DBU. However, the degrees of estrification with all these bases was much lower than that with DBU. © 1996 John Wiley & Sons, Inc.     

Synthesis and thermal self-crosslinking reaction of polymer containing spiro ortho ester and carboxylic acid

Polymers with both pendant spiro ortho ester and carboxylic acid moieties were synthesized by partial esterification of poly(methacrylic acid), poly(methacrylic acid-co-methyl methacrylate), or poly(methacrylic acid-co-styrene) with halomethylated spiro ortho esters in the presence of 1,8-diazabicyclo[5,4,0]undecene-7 in dimethyl sulfoxide. The extent of esterification increased with increasing reaction temperature. The reaction of polymeric carboxylic acids with chloromethylated spiro ortho esters proceeded to 80% of conversion at 100°C for 120 h. In contrast, the degree of esterification with bromomethylated spiro ortho ester reached 80% at 60°C within 24 h. Thermo-crosslinking of polymers having pendant spiro ortho ester moiety and carboxylic acid could be effected in films. The rate of spiro ortho ester ring-opening increased with increasing reaction temperature and with increasing content of carboxylic acid groups in the polymer. Further, the rates of gel production were also measured. The polymer containing an equimolar mixture of spiro ortho ester moieties and carboxylic acids exhibited the highest reactivity. In addition, it was found that thermal crosslinking reaction of the polymer occurred with minimum volume shrinkage.     

Partly Imidized Polyamic Acid and Its UniaxialStretched Polyimide Films

Partly imidized polyamic acid(PAA) has been used to prepare high performance polyimide films. The behaviors of two polyamic acids derived from pyromellitic dianhydride(PMDA)/4,4′-oxydianiline(ODA) and 3,3′,4,4′-biphenyltetracarboxylic diahhydride(BPDA)/paraphenylenediamine(PPD) containing dehydrating agents composed of acetic anhydride and a tertiary amine as the catalyst were investigated. The gel point was dependent on imidization degree in despite of temperature and the molar ratio of catalyst to acetic acid. Imdization content was about 35% for PMDA/ODA and about 22% for BPDA/PPD. The effect of catalyst on imidization possessed an order of triethylamine>3-methylpyridine>pyridine>isoquinoline>2-methylpyridine. The stretching of the films greatly reduced the coefficient of linear thermal expansion(CTE) either in the longitudinal direction or transversal direction. Compared to the film from polyamic acid, the partly imidized film had greater stretching ratio, so that the uniaxial stretched polyimide film from partly imidized PAA had higher tensile strength and tensile modulus, but lower elongation in the stretching direction.     

Photoreactive fluorinated polyimide protected by a tetrahydropyranyl group (THP) based on photo-induced acidolysis

A polyimide (6F-THP) with a tetrahydropyranyl group (THP) in its side chain has been synthesized. The THP group exhibits a high acidolysis rate in this polymer's film. This rate was faster than that of a tertbutoxycarbonyl group (t-BOC), which has been previously reported [1]. Furthermore, the deprotected fluorinated polyimide (6FDA-AHHFP) became soluble in an aqueous base due to the presence of a hydroxyl group attached to the phenyl group of the diamine segment. The polyimide thus provides high performance as a photopolymer when used in conjunction with a photoacid generator after the post-exposure baking process (PEB). The photoacid generators used in this study were p-nitrobenzyl-9,10-dimethoxyanthoracene-2-sulfonate (NBAS) and diphenyliodonium-9,10-dimethoxyanthoracene-2-sulfonate (DIAS). The quantum yields of photodissociation and photoacid generation were also measured. The photoacid-generating quantum yields closely corresponded to the photosensitivities of the photoreactive polyimide system. It was confirmed that the THP group was easily deprotected even in the 6F-THP film with p-toluenesulfonic acid as a model acid catalyst. The activation energy of the THP deprotection reaction was determined to be 12.8 kcal/mol (19.5 kcal/mol in the case of t-BOC). The relationships between the THP deprotecting rate constant (k_d) and acid molecular size and between k_d and polyimide structure were further investigated.     

旋光聚[乙烯-alt-R-N-(1-苯乙基)马来酰胺酸]的合成及静电自组装

以聚(乙烯-alt-马来酸酐)为原料,通过与R-(+)-α-苯乙胺的酰胺化反应,合成了一种新型的旋光聚电解质聚[乙烯-alt-R-N-(1-苯乙基)马来酰胺酸],利用红外吸收光谱、紫外吸收光谱、核磁共振氢谱和旋光度数据对其结构进行表征.聚[乙烯-alt-R-N-(1-苯乙基)马来酰胺酸]与聚二甲基二烯丙基氯化铵(PDDA)逐层静电自组装过程的紫外跟踪测试结果表明,带相反电荷的聚电解质间能够形成稳定增长的自组装膜,多层膜组装量随双层数指数增大.     

Porphyrin-containing polyimide films deposited by high vacuum co-evaporation

Thin films of porphyrin-containing polyimide were produced by high vacuum co-evaporation of 4,4′-hexafluoroisopropylidene diphthalic anhydride (6FDA), 3,3′-diaminodiphenyl sulfone (DDS) and 5,10,15,20 meso-tetraphenyl porphyrin (TPP). The films were characterized by FT-IR analysis, optical absorption and emission spectroscopy. FT-IR analysis shows that the film matrix is comprised of only unreacted monomers. The conversion of monomers to polyamic acid and the following condensation to polyimide were studied by curing the samples at temperatures up to 240 °C. The amount of polyamic acid increases from room temperature to 120 °C, while at higher temperature it starts to condense to polyimide. Optical analysis shows that TPP is incorporated in the film matrix and its chemical state is determined by the interaction with the monomers, polyamic acid and polyimide. After curing the TPP molecules are finely dispersed in the polyimide matrix and their absorption and fluorescence properties are wholly preserved.     

High modulus polyimide/polyimide molecular composite films that utilize acetylene unit as a crosslink site

Polyimide/polyimide molecular composite (MC) films comprised of a rigid polyimide derived from biphenyltetracarboxylic dianhydride (BPDA) and p-phenylenediamine (PDA) and a flexible polyimide derived from BPDA and bis (3,3'-diaminodiphenyl) acetylene (intA) and/or oxydianiline (ODA) were prepared by blending the polyamic acid solutions in 7 : 3 weight ratio, and then imidizing the blend films. Acetylene content in the flexible polyimide backbone was controlled by the ratio of intA and ODA. Cold-drawing of the blend polyamic acid films, followed by imidization, gives high modulus polyimide/polyimide MC films. The modulus of the MC films increased almost linearly with the draw ratio, reaching 25.5 GPa for the 40% drawn film. Acetylene groups in the flexible polyimide can be thermally cured to crosslink. The onset of exotherm appeared at 340°C on DSC, reaching maximum at 398°C. After the thermal crosslinking, the MC films maintained the high modulus, though elongation became small. Taking advantage of the crosslinkable acetylene units, two MC films were laminated and processed at 400°C for 20 min under 100 kg/cm² to give a good-quality laminate film. The interface of the two films was strongly bonded through the crosslinking of acetylene groups. Laminate films maintained the high modulus afforded by the cold-drawing. © 1994 John Wiley & Sons, Inc.     

Synthesis,photo-reaction and photo-induced liquid crystal alignment of soluble polyimide with pendant cinnamate group

In this paper, the synthesis, photo-reaction and photo-induced liquid crystal alignment of a polyimide with a pendant cinnamate group are reported. The polyimide was synthesized by the thermal imidization of the polyamic acid derived from 4,4'-(hexafluoro-isopropylidene)diphthalic anhydride and hydroxydiaminopropane, followed by the attachment of the cinnamate group to the main chain polyimide. The surface of thin layers of the polyimide was found to be preferentially occupied by the pendant cinnamate groups, and liquid crystal alignment on the polyimide thin film exposed to polarized UV was independent of the cinnamate content. The thermal stability of the photo-induced liquid crystal alignment was enhanced with decrease in the cinnamate content. This could be attributed to the strong interchain interaction of the polyimide chains which prevents thermal randomization of the photo-product of the pendant cinnamates. The dependences of the photo-reaction temperature and the annealing temperature of the alignment layer on the azimuthal anchoring energy of the photo-aligned liquid crystal suggest that the local stress developed during the UV irradiation profoundly influences the thermal stability of the liquid crystal alignment.     

Preparation of ultrathin films of aromatic polymides by vapor deposition polymerization from N-silylated aromatic diamines or aromatic tetracarboxylic dithioanhydride

A novel method for the preparation of ultrathin films of aromatic polyimides was developed through vapor deposition polymerization from combinations of monomer pairs of either N,N′-bis (trimethylsilyl)-substituted aromatic diamines and pyromellitic dianhydride or aromatic diamines and pyromellitic dithioanhydride. Both diamine component and tetracarboxylic dianhydride component were evaporated simultaneously at a stoichiometric molar ratio under vacuum, giving a deposited film on a substrate, which consisted of a polyamic acid derivative formed by the ring-opening polyaddition. The deposit was then converted to polyimide by thermal imidization at a relatively lower temperature, compared with a conventional method using the parent diamine and tetracarboxylic dianhydride. The properties of polyimide ultrathin films such as thermal stability, chemical resistance, and dielectric behavior were almost the same as those of the polyimide films prepared by a conventional method.     

Synthesis, photo-reaction and photo-induced liquid crystal alignment of soluble polyimide with pendant cinnamate group

In this paper, the synthesis, photo-reaction and photo-induced liquid crystal alignment of a polyimide with a pendant cinnamate group are reported. The polyimide was synthesized by the thermal imidization of the polyamic acid derived from 4,4'-(hexafluoro-isopropylidene)diphthalic anhydride and hydroxydiaminopropane, followed by the attachment of the cinnamate group to the main chain polyimide. The surface of thin layers of the polyimide was found to be preferentially occupied by the pendant cinnamate groups, and liquid crystal alignment on the polyimide thin film exposed to polarized UV was independent of the cinnamate content. The thermal stability of the photo-induced liquid crystal alignment was enhanced with decrease in the cinnamate content. This could be attributed to the strong interchain interaction of the polyimide chains which prevents thermal randomization of the photo-product of the pendant cinnamates. The dependences of the photo-reaction temperature and the annealing temperature of the alignment layer on the azimuthal anchoring energy of the photo-aligned liquid crystal suggest that the local stress developed during the UV irradiation profoundly influences the thermal stability of the liquid crystal alignment.     

Effect of curing accelerators on thermal imidization of polyamic acids at low temperature

The effect of new additives on the thermal conversion of a range of polyamic acids to polyimides at temperatures lower than 100°C was investigated using infrared spectroscopy. Additives such as m-hydroxybenzoic acid, p-hydroxyphenylacetic acid, and p-hydroxybenzenesulfonic acid were found to be highly effective as curing catalysts or accelerators. The degree of imidization of polyamic acids in the presence of additives increased with an increase in the reaction temperature, and complete imidization was achieved at 140–200°C. The reaction was characterized by a rapid rate that slowed with time. © 1996 John Wiley & Sons, Inc.     

Synthesis of polyimides from N,N′-bis(phenylsulfonyl)pyromellitimide and aromatic diamines

A novel and successful synthesis of polyimide has been performed by the two-step polymerization of N,N′-bis(phenylsulfonyl)pyromellitimide (BPSP) and bis(4-aminophenyl) ether (ODA). The ring-opening polyaddition reaction proceeded in N-methyl-2-pyrrolidone at room temperature through the formation of the open-chain polyamide, which was subsequently converted by heating to the polyimide along with the elimination of benzenesulfonamide. The polymerization of BPSP with ODA took place fairly rapidly to give the polyamide having inherent viscosity in the range of 0.6–0.8. The polyamide solution was resistant to hydrolysis, but was somewhat susceptible to imidization reaction. The thermal imidization of the open-chain polyamide occurred far more readily than that of the polyamic acid derived from pyromellitic dianhydride and ODA.     

Acid-Containing Tyrosine-Derived Polycarbonates: Wettability and Surface Reactivity

Tyrosine-derived polycarbonates having carboxylic acid pendant groups were characterized by water contact angle and X-ray photoelectron spectroscopy (XPS). A pronounce decrease of receding angle as well as contact angle hysteresis as a function of acid composition strongly indicated that the acid groups are more accessible at the water/polymer interface after hydration. pH dependent contact angle confirmed an existence of carboxylic acid groups in the surface region. The receding angle transition appearing in the pH range of 4-6 was a consequence of hydrophilicity change due to interconverting from carboxylic acid (-COOH) to carboxylate ion (-COO⁻). The surface compositions of imidazole-labeled polymers as analyzed by XPS were consistent with the bulk stoichiometry of the polymers. Reactivity of acid groups towards chemical reaction at the surface was also investigated. The acid groups at the surface of polymers were capable of adsorbing a significant amount of calcium ion from simulated body fluid and being activated by a reaction with N-hydroxysuccinimide.     

Preparation and morphological,electrical, and mechanical properties of polyimide‐grafted MWCNT/polyimide composite

Precursor of polyimide, polyamic acid has been prepared sucessfully. Acid‐modified carbon nanotube (MWCNT) was grafted with soluble polyimide then was added to the polyamic acid and heated to 300 °C to form polyimide/carbon nanotube composite via imidation. Morphology, mechanical properties and electrical resistivity of the MWCNT/polyimide composites have been studied. Transmission electron microscope microphotographs show that the diameter of soluble polyimide‐grafted MWCNT was increased from 30–60 nm to 200 nm, that is a thickness of 70–85 nm of the soluble polyimide was grafted on the MWCNT surface. PI‐g‐MWCNT was well dispersed in the polymer matrix. Percolation threshold of MWCNT/polyimide composites has been investigated. PI‐g‐MWCNT/PI composites exhibit lower electrical resistivity than that of the acid‐modified MWCNT/PI composites. The surface resistivity of 5.0 phr MWCNT/polyimide composites was 2.82 × 10⁸ Ω/cm² (PI‐g‐MWCNT) and 2.53 × 10⁹ Ω/cm² (acid‐modified MWCNT). The volume resistivity of 5.0 phr MWCNT/polyimide composites was 8.77 × 10⁶ Ω cm (PI‐g‐MWCNT) and 1.33 × 10¹³ Ω cm (acid‐modified MWCNT).Tensile strength and Young's modulus increased significantly with the increase of MWCNT content. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3349–3358, 2007     

Microbial Transformation of Ceanothic Acid and Derivatives by Mycobacterium sp. (NRRL B-3805)

Ceanothic acid (1) is the major triterpene isolated from Parliurus ramosissitnus (Rhamnaceae) which possesses three methyl groups corresponding to the 4,4,14α-trimethyl groups in lanosterol (5). Microbial transformation of 1 and its 3-dehydro-2,28-dimethyl ester derivative (3) with Mycobacterium sp. (NRRL B-3805) resulted in the methylation of the carboxylic functions and C-1 epimerization, respectively. Although this work indicates that 1 is not a suitable substrate for 4,4,14α-tridemethylation, esterification of the carboxylic function and the C-1 epimerization reaction in ceanothic acid and its derivative is the first observation with this microorganism.     

Formation of a highly ordered poly (N,N'-bis-phenoxyphenylpyromellitimide) powder using a high pressure curing technique

A high-pressure curing technique was developed to help determine the effects of solvent presence during the thermal curing of the polyimide poly (N,N'-bis-phenoxyphenylpyro-mellitimide) (PMDA-ODA). A powder form of this aromatic polyimide was produced from a polyamic acid solution using the high-pressure thermal curing technique. Preliminary characterization of the powder indicates a high degree of crystallinity with a measured density of 1.46 ± 0.01 g/cm³ and a distinct melting point of 594°C. The addition of chemical curing agents to the polyamic acid solution prior to thermal treatment reduced the amount of crystallinity observed in the cured material. Molecular weight measurements of the polyamic acid precursor and powder suggest that the high degree of order observed in the powder is a result of degradation during cure. © 1994 John Wiley & Sons, Inc.

1 This article is a US Government work and, as such, is in the public domain in the United States of America

     

FT-Raman investigation of the thermal curing of PMDA/ODA polyamic acids

The effect of solvent on the curing reactions of PMDA/ODA polyamic acids has been investigated using Fourier transform (FT)-Raman spectroscopy. Films of different thicknesses were cured by: (1) doctor blading 15% solids solutions onto glass slides, (2) removing all but the bound NMP, and (3) removing all the N-methypyrrolidinone (NMP). The rate of cure and final degree of conversion of the PMDA/ODA polyamic acid to polyimide increased substantially in the presence of NMP, and this effect was attributed to the plasticizing effect of the solvent. Below a critical solvent concentration, which was estimated to be approximately 40% of the NMP concentration in the bound-solvent limit, the rate of imidization slowed down considerably. Comparison of FT-Raman data for PMDA/ODA polyamic acid: (1) in solution in NMP, (2) complexed with NMP in the solid state, and (3) in the solid state after all the NMP had been removed with water, indicated that intermolecular interactions were greatest in the latter case and weakest in solution. Spectra of PMDA/ODA in NMP solution provide strong evidence for binding of NMP to the amide carbonyl in solution. © 1993 John Wiley & Sons, Inc.