Dianhydride Units Research Articles

Thermoplastic polyimide with low dielectric properties enabled by the 2,2′‐spirobifluorene group

AbstractThermoplastic polyimides (TPIs) have melt‐processability and adhesive ability, besides the intrinsic advantages of polyimides. To meet the requirements of applications in high‐frequency communication, TPIs with low dielectric constant (Dk)/dielectric loss factor (Df) at high frequency are also desirable. Enhancing the rigidity of polymer chains and simultaneously intermolecular interaction are effective ways to ensure low Dk/Df, which also benefit to heat resistance. However, it is not conducive to thermoplasticity, due to limited movement of polymer chains. To balance the trade‐off between them, we introduce noncoplanar 2,2′‐spirobifluorene groups to modify the rigidity of polymer chains and regulate the twist between electron‐donor moieties (diamine units) and electron‐acceptor moieties (dianhydride units). It leads to rigid polymer chains, which benefits to good heat resistance and dielectric properties. Meanwhile, the resultant irregular chain structure is difficult to crystallize, which results in thermoplasticity.

Symmetric All-Organic Battery Containing a Dual Redox-Active Polymer as Cathode and Anode Material.

All-organic batteries are a promising sustainable energy storage technology owing to the wide availability, flexibility, and recyclability of organic/polymeric compounds. The development of all-organic or polymer batteries is still a challenge, as both electrode materials need to be carefully optimized to have a wide difference of redox potential and compatibility with the electrolyte. Herein, dual redox-active polyimides based on phenothiazine and naphthalene tetracarboxylic dianhydride units are presented. After only one optimization step, the electrodes based on these dual redox polymers can be applied simultaneously as anode and cathode in a symmetric all-organic battery. The phenothiazine functional polyimide shows two redox active voltages at around 2.5 and 3.7 V (vs. Li/Li+ ) with high discharge capacities of 160 mAh g-1 . Moreover, the symmetric full battery delivers high power density up to 1542 W kg-1 with stable cyclability for 1000 cycles. This work demonstrates an efficient strategy to develop dual redox active polymer electrodes for next generation all-polymer batteries.

Molecular design of some semi-alicyclic polyimides as a route to improve refraction and dielectric properties for liquid crystal display applications

The study establishes an adequate monomer combination for achieving the best balance of properties required in obtaining polyimide alignment layers for display devices. The molecular design of some aliphatic/aromatic polyimides was performed by using dianhydride monomers with distinct configurations in terms of rigidity, size, and symmetry. The polyimides based on semi-flexible and nonsymmetric dianhydride moieties present lower refractive index and dielectric constant (<3) than those obtained from symmetric and rigid dianhydride units. This determines faster traveling of visible and microwave radiations as required for liquid crystal alignment purposes. The interactions of samples with the N-(4-Methoxybenzylidene)-4-butylaniline, cyanobiphenyl, and 4-pentyl-4-cyanobiphenyl nematics were assessed. The analyzed polyimides have higher surface tensions than the ones of the liquid crystals, determining a parallel arrangement of the nematic molecules. As the dispersive interactions at the polymer surface are lower, the work of spreading is higher as a result of improved adhesion of liquid crystal with the polyimide alignment layer. The sample containing rigid, symmetric, noncoplanar dianhydride units (PI.4) and the one based on semi-flexible, nonsymmetric dianhydride moieties are the most transparent for visible and microwave radiations, allowing low cohesion interaction at interface with nematics. These aspects recommend the two studied polyimides as candidates for alignment layers.

Preparation of robust, flexible, transparent films from partially aliphatic copolyimides

Robust, flexible, and transparent films have been prepared from partially aliphatic copolyimides, and their structure-property relationship was systematically studied. Spiro-type rel-(1′R,3S,5′S)-spiro[furan-3(2H),6′-[3]oxabicyclo[3.2.1]octane]-2,2′,4′,5(4H)-tetrone (DAn) and ladder-type 1,2,3,4-cyclopentanetetracarboxylic dianhydride (CPDA) were used as cycloaliphatic dianhydride. Each dianhydride and an aromatic dianhydride, benzophenone-3,3′,4,4′-tetracarboxylic dianhydride (BTDA), were polymerized with an aromatic diamine, 4,4′-oxydianiline (ODA). Molar feed ratio of the aliphatic and aromatic dianhydrides was varied, and the molar ratios of dianhydride units in the obtained poly(amic acid)s were in good agreement with the molar feed ratios. Highly flexible and transparent films were obtained from the copolyimides. The relationship between structure and properties such as film flexibility, solubility, optical transparency, and thermal stability is explained by intermolecular interactions, degree of intramolecular conjugation, intermolecular charge transfer complex formation and backbone flexibility including the measurement of d-spacing values by wide-angle X-ray diffraction (WAXD) analysis. The polyimide prepared with the molar feed ratio of DAn:BTDA:ODA of 0.9:0.1:1 gave thin films having high flexibility, transparency, and colorlessness coupled with good solubility, thermal stability, and mechanical properties. Open image in new window

Transparency and absorption edges of disiloxane modified copolyimides

Optical characteristics of two novel copolyimides prepared from an alicyclic or a fluorine-based dianhydride combined with an aliphatic siloxane-based diamine and an aromatic one containing ether linkages, are compared. Ellipsometry data show that the reduced polarizability, provided by the aliphatic moieties, leads to copolyimides with low refractive index (1.53–1.57). The corresponding dielectric constants decrease from 2.71 to 2.57 as the polarization of the dianhydride unit is reduced by the presence of CF3 groups. The transmittance is of approx. 90% and the cut-off wavelengths are comprised between 336 and 380nm. The values of optical band-gap are higher for the fluorine-based copolyimide, namely 3.00eV comparatively to 2.34eV for the sample with alicyclic dianhydride sequences, indicating a lower probability of optical absorption transitions and thus a better transparency. The Urbach and Tauc energies changed in the range of 2295–2809meV and 893–1161meV, being smaller as the polarizability is diminished by the presence of CF3 groups. Optical properties are correlated with morphological aspects, namely surface roughness parameters and entropy of morphology, which varies in agreement with the refractive indices of copolymers.

Aggregation behavior of organic-soluble semi-aromatic polyimides in N -methylpyrrolidone systems

Aggregation behavior of the organic-soluble semi-aromatic polyimides, whose degrees of imidization range from 69 to 96%, obtained using 4,4′-oxydianiline, 4,4′-diamino-3,3′dihydroxybiphenyl, and bicyclo[2.2.2]-oct-7-ene-2,3,5,6-tetracarboxylic dianhydride (BCDA) in N-methylpyrrolidone (NMP), NMP/cyclohexanone, and NMP/γ-butyrolactone (BCDA-based polyimides) were studied by static light scattering (SLS) and dynamic light scattering (DLS). The DLS analyses for the multirelaxation modes demonstrated the specific character unlike flexible polymers that the single BCDA-based polyimide chains first associate with each other to form small clusters in the dilute region, and then expand to large aggregates by the entanglements between the small clusters with an increasing concentration into the semi-dilute region. Given the semi-aromatic structure of BCDA-based polyimides weakening the charge transfer (CT) interaction between the diamine and the dianhydride unit, it is concluded that the unique aggregation behavior of BCDA-based polyimides is dominated by the balance between the driving force for the “organic solubility” given by both the increase in bulkiness and the decrease in the CT interaction, and that for the “organic insolubility” derived from both the hydrogen-bonded interaction of the phenolic hydroxyl groups and the π–π interaction of the phenyl rings. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012

Morphology and Dielectric Property of Cellular Polyimide Films Prepared by Phase Inversion

In order to explore low dielectric polymeric materials, two types of cellular polyimide films with different dianhydride units were prepared by phase inversion method, and their dielectric properties were investigated. Polyimide films with various cellular structures were obtained by controlling coagulation bath compositions and temperatures. The effects of chemical structures, cellular structures on dielectric property of cellular polyimide films were studied. The results showed that all of the cellular polyimide films had lower dielectric constants than the polymer matrix. The dielectric properties were influenced dominantly by the morphologies of the films. Cellular Polyimide films filled with uniform small cellular structures behaved excellent dielectric property compared with those large-pore cellular films. These findings would provide potential application for cellular polyimide films in microelectronic devices.

Optical Measurements of Polyimide Films in UV and VUV Regions

Absorption and reflection measurements of polyimides (PIs) PMDA-BAPP, BTDA-BAPP, and CBDA-BAPP were performed using synchrotron radiation as a light source in UV and VUV regions. Absorption spectra were obtained by Kramers-Kronig analyses from reflection spectra. Molecular orbital calculations were performed for model PI compounds. Optical transitions at the absorption tails of aromatic PIs (PMDA-BAPP and BTDA-BAPP) are characteristic of localized electronic transitions of dianhydride units while those at the absorption tail of semi-aromatic PI (CBDA-BAPP) are characteristic of charge transfer transitions. At high-energy regions, phenyl-group π-π* transitions are observed at about 6.2 eV. Very strong absorption peaks are also observed at about 16.0 eV for aromatic PIs and at about 15.0 eV for semi-aromatic PI. These results are characteristic of optical transitions from HOMO-level C 2p orbitals to high-energy region C 2p orbitals above LUMO levels.

Synthesis and properties of novel polyimides from sulfonated binaphthalene dianhydride for proton exchange membranes

AbstractA sulfonated dianhydride monomer, 6,6′‐disulfonic‐4,4′‐binaphthyl‐1,1′,8,8′‐tetracarboxylic dianhydride (SBTDA), was successfully synthesized by direct sulfonation of the parent dianhydride, 4,4′‐binaphthyl‐1,1′,8,8′‐tetracarboxylic dianhydride (BTDA), using fuming sulfuric acid as the sulfonating reagent. A series of sulfonated homopolyimides were prepared from SBTDA and various common nonsulfonated diamines. The resulting polymer electrolytes, which contain ion conductivity sites on the deactivated positions of the aryl backbone rings, displayed high proton conductivities of 0.25–0.31 S cm−1 at 80 °C. The oxidative stability test indicated that the attachment of the SO3H groups onto the dianhydride units did not deteriorate the oxidative stability of the SPI membranes. The better membranes were achieved by the copolymerization of nonsulfonated diamine, SBTDA, and BTDA. Copolymer membrane synthesized from hexane‐1,6‐diamine, SBTDA, and BTDA displayed excellent water stability of more than 1000 h at 90 °C, while its proton conductivity was still at a high level (comparable to that of Nafion 117). Furthermore, the novel block copolymer (II‐b) displayed higher proton conductivity compared with the random one (II‐r) obviously, probably due to the slightly higher water uptake and better microphase separated morphology. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2820–2832, 2008

Transport properties of polyimides containing phenylquinoxaline moieties

The gas permeabilities of a number of new structurally related polyimides containing phenylquinoxaline moieties were studied for the first time. The test polymers had different dianhydride units, whereas their diamine components differed in the presence of flexible ether bonds-O-in the main chain, a structure that is reflected in the effective packing of chains and, as a result, in transport parameters. The permeability, diffusion, and solubility coefficients for the gases H2, He, O2, N2, CO, CO2, and CH4, as well as the ideal separation factors for gas pairs, were determined. The transport characteristics of polymers were compared within the given polymer series and with published data for other polymer series.

Synthesis and properties of novel soluble polyimides having a spirobisindane-linked dianhydride unit

A new synthetic procedure was elaborated allowing the preparation of semiaromatic dianhydride. N-Methyl protected 4-chlorophthalic anhydride was nitrated with HNO3 to produce N-methyl-4-chloro-5-nitrophthalimide (1). The aromatic nucleophilic substitution reaction between 5,5′,6,6′-tetrahydroxy-3,3,3′,3′-tetramethyl-1,1-spirobisindane and 1 afforded spirobisindane-linked bis(N-methylphthalimide) (2), which was hydrolyzed and subsequently dehydrated to give the corresponding dianhydride (3). The latter was polymerized with five different aromatic diamines to afford a series of aromatic polyimides. The properties of polyimides such as inherent viscosity, solubility, UV transparency and thermal stability were investigated to illustrate the contribution of the introduction of spirobisindane groups into the polyimide backbone. The resulting polyimides were readily soluble in polar solvents such as chloroform, THF and N-methyl-2-pyrrolidone. The glass-transition temperatures of these polyimides were in the range of 254–292°C. The tensile strength, elongation at break, and Young's modulus of the polyimide film were 68.8–106.6MPa, 5.9–9.8%, 1.7–2.0GPa, respectively. The polymer films were colorless and transparent with the absorption cutoff wavelength at 286–308nm.

Synthesis and properties of novel soluble polyimides having an unsymmetric spiro tricyclic dianhydride unit

A novel spiro trialicyclic dianhydride, rel[1S,5R,6R]-3-oxabicyclo[3.2.1]octane-2,4-dione-6-spiro-3′-(tetrahydrofuran-2′,5′-dione) (DAn) was synthesized from itaconic anhydride (1) and cyclopentadiene via a Diels-Alder reaction, nitric acid oxidation, and the subsequent dehydration with acetic anhydride. The structure of DAn was determined by NMR spectra and single crystal X-ray diffraction. A series of soluble polyimides (PIs) having a spiro alicyclic unit in the main chain were prepared by the reactions of DAn with several diamines through a general two-step polymerization method. Polymerization temperature affected inherent viscosities of poly(amic acid)s. Chemically imidized PIs had the inherent viscosities in the range of 0.10–0.49 dL/g. Due to the unsymmetric spiro alicyclic structure, the PIs showed excellent solubility in many organic solvents. Glass transition temperatures of PIs ranged from 215 to 279°C and some of them showed no glass transition temperature. The 10% weight loss temperatures under nitrogen were in a range of 355–430°C. Films of PIs obtained by the thermal imidization were wholly transparent and colorless.

Synthesis and Resist Evaluation of Photosensitive Polyimides

We have synthesized novel photodegradable polyimides with sulfonyloxyimide units in the polymer main chain. The yield and molecular weight of polyimides were significantly influenced by polymerization condition and monomer structure. The prepared polyimides were stable up to 300°C. The effects of polymer structure on photodegradable characteristics were examined. The photodegradation of polyimides upon irradiation with deep UV resulted from scission of N-O bonds or ring opening of imide moiety. The polyimides are useful as positive working photodegradable polymers. Especially, it has been found that the positive tone image of polyimide derived from pyromellitic dianhydride units has high sensitivity and resolution.

Synthesis and properties of polyimides derived from isomeric biphenyltetracarboxylic dianhydrides

2,2′,3,3′-Biphenyltetracarboxylic dianhydride (i-BPDA) was suggested as a monomer for the synthesis of soluble polyimides with high thermal stability, and an efficient method of its preparation has been developed. Polyimides derived from i-BPDA and aromatic diamines (i.e. 4,4′-oxydianiline, 2,2′-bis(trifluoromethyl)benzidine and 9,9′-fluorenylidene-4,4′-dianiline) showed high glass transition ( T g>330°C) and degradation ( T d5>550°C) temperatures, and were soluble in organic solvents (i.e. NMP, DMF, γ-butyrolacton, CHCl 3), although their mechanical properties were inferior to those of polyimides composed of semirigid 3,3′,4,4′-biphenyltetracarboxylic dianhydride (s-BPDA). Random copolymers, derived from i-BPDA and s-BPDA, retained superior mechanical properties of s-BPDA-based polyimides and showed improved solubilities, depending on the i-BPDA content. A regular increase of glass transition temperatures and a decrease of inherent viscosities of copolymers with increasing content of i-BPDA was observed, whereas the dielectric constants and degradation temperatures were found to be independent of the ratios of dianhydride units.

Preparation and properties of novel soluble aromatic polyetherimides from 1,1′-bis[4-(3,4-dicarboxyphenoxy) phenyl]-1-phenyl-2,2,2-trifluoroethane dianhydride and aromatic diamines

New aromatic polyetherimides containing the 1,1′-bis[4-(3,4-dicarboxyphenoxy)phenyl]-1-phenyl-2,2,2-trifluoroethane dianhydride unit were prepared by a conventional two-step method from 1,1′-bis[4-(3,4-dicarboxyphenoxy)phenyl]-1-phenyl-2,2,2-trifluoroethane dianhydride and several diamines. This procedure yielded high molecular weight polyetherimides with inherent viscosities of 0.22–1.29 dL/g. Most of the corresponding polyetherimides were soluble in organic solvents such as N-methyl-2-pyrrolidone, N, N-dimethylformamide, N,N-dimethylacetamide, and methylene chloride under ambient temperature. The glass transition temperatures (Tg) of these polymers were in the range of 207–264°C and the temperatures of 10% weight loss were over 520°C at a heating rate 20°C/min in nitrogen. © 1996 John Wiley & Sons, Inc.