The role of the pyrimidine ring in the main chain of polyamic acids and polyimides

Thermoimidization kinetics of polypyromellitamic acids prepared from 2,5-bis(p-aminophenyl)pyrimidine and 4,4-diaminoterphenyl have been investigated by IR spectroscopy. It has been shown that the activation energy for the pyrimidine-containing polymer is nearly twice as low as that for the aromatic analog. This is explained by base catalysis of cyclization of the amidoacid fragments by pyrimidine rings in polymer chains. Base catalysis facilitates the process of imidization and favors the formation of polyimidic macromolecules with a lower incidence of defects. Also, the pyrimidine rings obviously catalyze the resynthesis of amidoacid fragments from the anhydride rings and amino groups formed on the destruction of the polymer chain during thermoimidization, and ensure almost complete recovery of the macromolecules with the previous bonds.For part 3, see Ref. 1.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 429–432, March, 1994.The authors are grateful to T. K. Meleshko for consultations about chemical imidization.     

The role of the pyrimidine ring in the main chain of polyamic acids and polyimides

A comparative study of the behavior of polypyromellitamic acids based on 2,5-bis(p-aminophenyl)pyrimidine and 4,4″-diaminoterphenyl in concentrated dimethylacetamide solutions was carried out by the light-scattering method. It was shown that mutual ordering of the scattering elements is much higher for the pyrimidine-containing polyamic acids than for benzenoid polyamic acids. The Flory-Huggins parameters of the polymer-solvent interaction thus determined indicate that the polymer-polymer interactions increase when a pyrimidine ring is introduced into the polyamic acid or polyimide. Hence, the hypothesis postulating that the amide solvent is displaced by the pyrimidine ring during the shear packing of pyrimidine-containing polymers is confirmed.     

Conjugated polymers containing phenothiazine moieties in the main chain

Several conjugated polymers containing phenothiazine moieties in the main chain were synthesized by Knovenagel or Wittig condensations. The polymers were identified and characterized by ¹H‐NMR, IR, gel permeation chromatography (GPC), thermogravimetric analysis (TGA), UV‐vis and fluorescent (FL) spectra. Results indicated that the m‐polymer, which was prepared from the polycondensation of N‐octyl‐3,7‐diformylphenothiazine with m‐phenylene diacetonitrile, is the most thermally stable one in all the polymers synthesized. While, the p‐polymer, which was prepared from the polycondensation of N‐octyl‐3,7‐diformylphenothiazine with p‐phenylene diacetonitrile, is the most thermally instable one. The introduction of a cyano group made the absorption and emissive maxima red‐shift from 429 and 537 nm for the Ph‐polymer to 465 and 597 nm for the p‐polymer respectively. The quinoid structure formation allows the p‐polymer to have a lower band gap than any other polymers. Emissive spectra of all these polymers in tetrahydrofuran (THF) solution have a narrow half‐peak width. Copyright © 2006 John Wiley & Sons, Ltd.     

Photochemical reactions of a dimethacrylate compound containing a chalcone moiety in the main chain

We synthesized the new photosensitive oligomer containing a chalcone moiety in the main chain by end-capping reaction of diepoxide compound with methacrylic acid. The chalcone-epoxy oligomeric compound was synthesized with 4,4^′-dihydroxychalcone and epichlorohydrin. Investigation of the photosensitivity of the newly synthesized chalcone oligomer was carried out by using UV-Vis absorption and infrared spectroscopies under UV exposure. We observed the photodimerization behavior under UV irradiation. At the same time, we could also observe the photopolymerization of the compound with a trace amount of dimethoxyphenyl acetophenone. Thermal properties of UV-cured dimethacrylate compounds were also studied.     

Synthesis of polyethers containing cyclodipeptide moiety in the main chain

The dichlorodihydropyrazines derived from 2,5‐diketopiperazine were treated with diols in a basic condition to afford polyethers containing cyclodipeptide moiety in the main chain, which were found to be degraded into amino acid components in an acidic condition. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 927–933, 2001     

Preparation of a new polymer containing photoluminescent pyrazoline unit in the main chain

A novel photoluminescent polymer (PPyne) containing a 2‐pyrazoline unit in the molecular main chain was prepared (for the first time) by polycondensation between a 2‐pyrazoline monomer [an adduct of 2,6‐bis(4‐bromobenzylidene)cyclohexanone with phenylhydrazine] and 2,5‐dihexyloxy‐p‐phenylene diboric ester in the presence of Pd(PPh₃)₄. PPyne had a number‐average molecular weight of 7800 and a polydispersity index of 1.99 and showed good solubility in common organic solvents. In toluene PPyne exhibited an intrinsic viscosity [η] of 0.42 dL g^?1 at 30 °C. The polymer was photoluminescent (PL) in both the chloroform solution and the solid state; the quantum yield of PL in the solution was 40%. In the two states, PPyne gave the same ultraviolet–visible (UV–vis) peak at 368 nm and the same PL peak at 512 nm. DSC traces indicated that PPyne had a melting temperature of 168 °C, and thermogravimetric analysis revealed that the polymer had good thermal stability with a 5 wt % loss temperature of 376 °C under N₂. Electrochemical oxidation of PPyne started at about 0.5 V versus Ag/AgNO₃ and gave a peak at 0.98 V versus Ag/AgNO₃ with a color change of the film from yellow to black green. The color change was followed by UV–vis spectroscopy. The corresponding reduction peak appeared at 0.80 V versus Ag/AgNO₃. Treatment of PPyne with HCl led to dehydrogenating transformation of the polymer to a new cross‐conjugated polymer. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2686–2697, 2004     

Synthesis of polyester and copolyesters having amino acid moieties in the main chain

N, N-di (2-hydroxyethyl)-3-aminopropionic acid (M3) was synthesized and used for the preparation of a series of polyesters having amino acid moieties in the main chain and carboxyl groups as the side group. Polycondensation of M3 , diols, bisphenol A, and isophthaloyl dichloride were performed in the presence of tertiary amine by solution and interfacial methods. Molecular weights of the polymers obtained by the solution method were not high, because oligomers produced at the early stage of reaction are ionized by H⁺ ions from the by-product, and become nonreactive triethylamine hydrochloride. Polymers with high M?_w (1–10 × 10⁴) were obtained in a high yield by organic/organic two-phase interfacial polycondensation using DMAc and n-heptane as solvents. The combined nucleophilic and basic complex catalytic action of N, N, N′, N′-tetramethyl ethyiene diamine (TEMED) is suggested for the present organic phase/organic phase interfacial polycondensation. This method can be applied for the preparation of novel functional polyesters. © 1994 John Wiley & Sons, Inc.     

Green synthesis of polymers containing phosphorus in the main chain

New structures of polymers containing phosphorus in the main chain were prepared by interfacial polycondensation of phenylphosphonic dichloride with 4,4’-(1,3-phenylenediisopropylidene) bisphenol (bisphenol M) using two different methods: method I: gas–liquid interfacial polycondensation without an organic solvent and a catalyst; and method II: solid–liquid interfacial polycondensation using green solvents and without catalyst. The aim of this work was to apply these methodologies as eco-friendly and economical procedures for a green chemistry. The polymers were characterized by gel permeation chromatography (GPC), FT-IR, ¹H and ³¹P-NMR spectroscopy, differential scanning calorimetry (DSC) and thermal analysis. Yields in the range of 88.0–90.0, and inherent viscosities in the range of 2.2–3.2 dl/g were obtained. High molecular weight polymers (57 600–114 400) have been successfully prepared. The polymers are self-extinguishing and begin to lose weight at around 300 °C. The flammability was investigated by measuring limiting oxygen index values (LOI).     

Thermostability of polymers containing indanic units in the main chain

The acid-catalyzed stepwise polymerization of 1,1-diphenylethylene derivatives, p-di(1-phenylvinyl) benzene, bis[p-(1-phenylvinyl)phenyl]methane, 1,2-bis[p-(1-phenylvinyl)phenyl]ethane, bis[p-(1-phenylvinyl)phenyl]ether, and bis[p-(1-phenylvinyl)phenyl]sulfide produced selectively indanic-unit-containing polymers in pertinent conditions. Their molecular weights (M?_n) were in the 1600–15, 700 region after the fractionation in hot ethnol. Melting points were in the 214–281°C region. They dissolved fairly well in conventional solvents like benzene, tetrahydrofuran, and carbon tetrachloride. According to TGA they started to decompose at 397–432°C and showed 10% weight loss at 478–502°C in air at a heating rate of 5°C/min. Focusing on the thermostability, we report on their physical properties.     

Condensation polymers containing silicon and germanium in the main chain

Poly(carbonates), poly(thiocarbonates) and poly(esteres) containing silicon and/or germanium in the main chain were obtained under phase transfer conditions. Polymers were synthesized in a biphasic system NaOH/CH₂Cl₂ at 20°C using several phase transfer catalysts, and characterized by IR and ¹H and ¹³C NMR. The results were evaluated by the yields and the inherent viscosity values. The process was effective observing an increase of both parameters in comparison with the essays without catalyst. The increases depended of the nature of the polymer and the catalyst. In poly(ester) synthesis there was an increase of these parameters when the NaOH concentration was increased due to a salting out effect of the diphenolate from the aqueous phase to the organic one. Also poly(amides) containing silicon or germanium were synthesized by solution polymerization.     

Studies of poly-yne polymers containing transition metals in the main chain : III. Synthesis and characterization of a poly-yne polymer containing mixed metals in the main chain,

By the reaction of trans-(PBu₃)₂Pt(CCCCH)₂ with trans-(PBu₃)₂PdCl₂, the title polymer,

(II), has been prepared and characterized by spectral and analytical data. The alternating regularity of the metal arrangement in II was confirmed by the selective formation of the trinuclear complex trans,trans,trans-ClPd(PBu₃)₂?CCC CPt(PBu₃)₂?CC-CCPd(PBu₃)₂(XXIII), in the depolymerization by trans- (PBu₃)₂PdCl₂ using CuI as catalyst in XXNEt₂.     

Polysiloxane‐containing benzoxazine moieties in the main chain

Polysiloxanes containing thermally curable benzoxazine units in the main chain have been synthesized. For this purpose, first the diallyl functional benzoxazine monomer is synthesized through the Mannich and respective ring closing reactions of 4,4′‐isopropylidenediphenol (bisphenol A), formaldehyde, and allyamine. Subsequent hydrosilylation reaction of the resulting allylic monomer (B‐ala) with 1,1,3,3‐tetramethyldisiloxane (TMDS) in the presence of Pt catalyst yields the corresponding oligo(B‐ala‐tetramethyldisiloxane)s (OBTMDS). Using the anionic polymerization route, OBTMDS was then converted to poly(bisbenzoxazinedimethylsiloxane)s (PBDMSs) by reacting with readily available cyclic oligomer octamethylcyclotetrasiloxane (D4) or decamethylcyclopentasiloxane (D5) in the presence of tetrabutylammonium hydroxide as catalyst. The structures of the precursor diallyl monomer, the intermediate oligomer, and the resulting polymers are confirmed by Fourier transform infrared and ¹H NMR analysis. Curing behavior of the products at various stages has also been studied by differential scanning calorimetry. Flexible transparent films of the PBDMSs are obtained by solvent casting. Thermal properties of the cured polymers are also investigated by thermogravimetric analysis. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Synthesis,properties, and molecular simulations of high-barrier polyimide containing carbazole moiety and amide group in the main chain

An intrinsic high-barrier polyimide (2,7-CPAPPI) containing rigid planar carbazole moiety and amide group in main chain was prepared. The 2,7-CPAPPI shows very attractive barrier performances, possessing water vapor transmission rate (WVTR) and oxygen transmission rate (OTR) low to 0.04 g m⁻² day⁻¹ and 0.11 cm³ m⁻² day⁻¹, respectively. Meanwhile, 2,7-CPAPPI also displays exceptional thermal stability with a glass transition temperature (T_g) of 552°C and coefficient of thermal expansion (CTE) of 15.48 ppm/K. The barrier performances of 2,7-CPAPPI are compared with those of a structural analog (2,7-CPPI, containing only carbazole moiety in the main chain) and a typical polyimide (Kapton). The structure–barrier performances relationship was investigated by molecular simulations, wide angle X-ray diffraction (WAXD), and positron annihilation lifetime spectroscopy (PALS). The results show that 2,7-CPAPPI has more number of intermolecular hydrogen bonds among the three PIs, which leads to close chain packing and thereby high crystallinity, low free volume, and poor chains mobility. That is, the high crystallinity and low free volume of 2,7-CPAPPI decrease the diffusion and solubility of gases. Meanwhile, the poor chains mobility further reduces the gases diffusion. The decreased diffusion and solubility of gases consequently promote the improvement of barrier properties for 2,7-CPAPPI.     

Synthesis of polymer containing o-nitrobenzyl ether structure in the main chain

The polycondensation of nitrated xylenedihalides with diphenols was carried out under various conditions. The polycondensation of 2-nitro-1, 3-xylylenedibromide (NXDB) with 4,4′-isopropylidenediphenol proceeded in competition with the decomposition of polymer in the mixed solvent of tetrahydrofuran (THF) and dimethylsulfoxide (DMSO). The viscosity of the resulting polymer was markedly affected by the concentration of aqueous sodium hydroxide, reaction time, and reaction temperature. When dibromomethane was used as a solvent, the polycondensation proceeded very smoothly without the decomposition to give a higher reduced viscosity polymer than that in THF-DMSO at 60°C. The polymer obtained in dibromomethane contained a very small amount of formal bonds determined from the ¹H-NMR spectrum. The formation of formal bonds seems to cause the molecular weight in increase. Furthemore, the polycondensation of NXDB with 2,2-bis (4-hydroxyphenyl) hexafluoropropane afforded high molecular-weight polyether in dibromomethane. However, either high reaction temperatures or the high concentrations of aqueous potassium hydroxide solution casused the viscosity of the resulting polymer to decrease during the polycondensation in dibromomethane. The obtained polyethers with o-nitrobenzyl groups showed relatively good solubility, and decomposed smoothly upon the irradiation with UV light. Therefore, these polymers might be useful for positive type photoresists.     

Gas permeation and positron annihilation lifetime spectroscopy of poly(ether imides) containing main chain ethylene oxide segments

This article reports a study of four poly(ether imide)s with varying ethylene oxide (EO) segments lengths using positron annihilation lifetimes spectroscopy, wide angle X‐ray diffraction, and gas transport measurements. The measured properties change with the length of the EO segment. Comparison of the poly(ether imide) containing a single ether linkage with those containing one and three EO units, show progressive changes of the permeability and diffusion coefficient with void size. However, when six EO units are incorporated into the polymer backbone certain of the observed trends are reversed. Incorporation of flexible EO segments in the polymer backbone allows changes in the chain–chain interactions which increases the packing density and changes the void size and influences the solubility coefficients leading to variation of the gas transport characteristics. Differences in the measured solubility parameters reflect the extent to which the gases molecules are able to interact with the polymer matrix. The highest values obtained for the gas separation for carbon dioxide and nitrogen is observed when EO has a value of three. Further increasing of the length of the EO segments in the poly(ether imide) leads to a reduction the gas transport properties and hence the extent to which gas separation would be achieved. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1654–1662     

Photo-responsive behavior of a monolayer composed of an azobenzene containing polypeptide in the main chain

A photoresponsive polypeptide, two -helical poly(-methyl L-glutamate)s joined with an azobenzene (MAzoM,Mn=11000), have been prepared. Monolayers of the polypeptide were formed at air-water interface and the photoresponsive behavior of the monolayer obtained was investigated. A trans to cis photo-isomerization of the azobenzene moiety in the main chain of MAzoM induced by UV light irradiation resulted in a bending structure formation in the main chain of the polypeptide via photo-induced changes in the geometry of the azobenzene chromophore. As a result, the limiting area per molecule of the MAzoM monolayer was decreased. Based on the degree of the decrease in the limiting area per molecule, it was estimated that the bending angle between the two -helical rods of MAzoM molecule under UV light irradiation was ca. 140°. The photo-responsive behavior of the MAzoM monolayer was reversible and consisted along with the photo-isomerization of azobenzene moiety.     

Synthesis and fluorescent properties of conjugated copolymers containing maleimide and fluorene units at the main chain

Yamamoto or Suzuki–Miyaura coupling polymerizations of 2,3‐diiodo‐N‐cyclohexylmaleimide with fluorene derivatives (2,7‐dibromo‐9,9′‐dihexylfluorene and 9,9′‐dihexylfluorene‐2,7‐diboronic acid) were carried out. The number‐average molecular weights (M_n) of the resulting copolymers were 2600–3500 by gel permeation chromatography analysis. The fluorescence emission of the alternating copolymer showed the emission maxima at 551 nm in THF. On the other hand, the random copolymers showed the bimodal emission peaks at 418–420 and 555–557 nm region, respectively. The fluorescence peaks of the random copolymers on the long wavelength region (555–557 nm) were attributed to the conjugated neighboring N‐cyclohexylmaleimide‐9,9′‐dihexylfluorene units in the polymer main chain. Furthermore, the copolymers exhibited the fluorescence solvatochromism by the difference of the polarity of solvents. The alternating and random copolymers showed the different fluorescence solvatochromism, and the emission colors are distinguishable by the naked eye, respectively. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4945–4956     

Synthesis and characterization of soluble,blue-fluorescent polyamides and polyimides containing substituted p-terphenyl as well as long aliphatic segments in the main chain

A novel class of semiflexible polyamides and polyimides bearing substituted p-terphenyl as well as long aliphatic segments in the main chain were synthesized through pyrylium salts. Characterization of polymers was accomplished by inherent viscosity, elemental analysis, FT-IR, NMR, UV-vis luminescence spectroscopy, X-ray analysis, differential scanning calorimetry, thermomechanical analysis, thermogravimetric analysis, isothermal gravimetric analysis, and water uptake measurements. Polyamides displayed a degree of crystallinity and dissolved in polar aprotic solvents containing lithium chloride, as well as in trichloroacetic acid. Polyimides were amorphous and showed an excellent solubility, being soluble in various common solvents. The solutions of polyamides in DMF were blue-fluorescent with maxima at 362–370 nm. The emission maxima were not influenced appreciably upon the structure of the pendent groups and the length of the aliphatic spacers of backbone. The polymers possessed T_gs at 98–131°C and exhibited a satisfactory thermal stability. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3646–3656, 1999     

Ring dehydration mechanisms and kinetics of polyamic acid models in solution and in the solid state

We have synthesized and studied the ring dehydration mechanisms and kinetics of polyamic acid models in solution and in the solid state using ¹³C-NMR (solid and liquid), HPLC, FTIR, and x-ray diffraction. Results obtained in solution show the role of temperature, catalysts, and the basicity of the amine in ring dehydration mechanisms and kinetics, as well as conformation and intramolecular bonds in the amic acid bond in the solid state. © 1993 John Wiley & Sons, Inc.