Semi-alicyclic Polyimides Research Articles

Preparation and Properties of High-whiteness Polyimide Ultrafine Fabrics by Electrospinning from Organo-soluble Semi-alicyclic Polyimide Resins

Preparation and Properties of High-whiteness Polyimide Ultrafine Fabrics by Electrospinning from Organo-soluble Semi-alicyclic Polyimide Resins

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.

Evaluation of blood cells and proteins spreading on imidic polymers containing alicyclic sequences

A new polyimide containing alicyclic units is investigated in regard to a fully aromatic commercial one in order to assess their hemocompatibility. The rheological, structural, and surface properties of these two polyimides are analyzed by infrared spectroscopy and contact angle measurements. Flow activation energy of polyimide solutions is almost doubled when passing from 8 to 16 %, as an indicative of chain entanglement which enhances film formation ability. The surface tension components are obtained using the Fowkes method, revealing a slightly lower polar component (20.19 mN/m) for the semi-alicyclic polyimide, comparative with the aromatic one (22.52 mN/m). The hemocompatibility is theoretically established from calculation of the spreading work of blood cells and proteins on the polymer surface. The reduced polarizability and high flexibility of the alicyclic units from the new polyimide lead to improved hemocompatibility, as observed from the higher cohesion of blood components with this sample surface, comparative with the aromatic one.

Semi-alicyclic polyimide precursors: structural, optical and biointerface evaluations

Structural, optical and biointerface properties of two semi-alicyclic polyimide precursors have been investigated. The refractive index values are around 1.6, reflecting the impact of the polymer chain polarizability. The presence of the ethylene groups in the diamine residues leads to a higher transmittance of appreciatively 80 %. Optical energies describing absorption limits were determined using the approach of Tauc for amorphous materials, reflecting similar shape of the absorption edges with amorphous materials. The polymer with ethylene groups in the diamine moieties has an optical band-gap of 3.09 eV, indicating a lower probability of optical absorption transitions and thus a good transparency. Biointerface properties, namely the interactions occurring at polymer–blood interface, have been evaluated from the balance between the forces of adhesion and cohesion, before and after plasma treatment. Plasma active species enhance polymer surface polarity over 50 % so that the interfacial blood/sample tension is low enough to indicate a good hemocompatibility.

Origin of rheological behavior and surface/interfacial properties of some semi-alicyclic polyimides for biomedical applications

High-performance alicyclic-containing polyimides for advanced applications, derived from 5-(2,5-dioxotetrahydrofurfuryl)-3-methyl-3-cyclohexene-1,2-dicarboxylic acid anhydride or bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride and two flexible aromatic diamines, were synthesized by a classical two-step polycondensation reaction and analyzed by rheological method. The results were discussed according to the chemical structure of polyimides and their different properties, such as flexibility, hydrophobicity and surface morphology. It has been showed that the obtained parameters, controlled by the interactions occurring in the polyimide systems, can be correlated with the adhesion/cohesion of blood components and plasma proteins. Thus, the results of the work of spreading proteins on the hydrophobic polyimide surfaces indicated that albumin is not absorbed preferentially, while fibrinogen is characterized by a higher degree of adhesion on the surfaces, and also that selective adsorption of plasma proteins modifies blood compatibility. In addition, these results and the ascertained antimicrobial activity of the studied polyimides contribute to the development of new applications in the bio-technical field.

Morphological effects on transparency and absorption edges of some semi-alicyclic polyimides

Some novel semi-alicyclic polyimides based on epiclon and three aromatic diamines are investigated. The ellipsometry data reveal that the reduced polarizability provided by the alicyclic dianhydride moieties leads to polyimides with low refractive index, ranging from 1.64 to 1.72. The corresponding dielectric constants decrease from 2.97 to 2.71 as the polarization of the diamine part is lower. The transmittance is of appreciatively 90 % for polyimides containing methylene groups in the diamine residue. The cut-off wavelength decreases, as the backbone conjugation is smaller, being comprised between 305 nm and 317 nm — values comparable to that of a fully aliphatic PI. To obtain the optical energies describing absorption limits, the approach proposed by Tauc and Davis-Mott has been used, due to the similarity of the absorption edges. The values of optical band-gap are found from 3.51 to above 3.78 eV, indicating a low probability of optical absorption transitions and thus a good transparency. The Urbach and Tauc energies changed in the range of 480–806 meV and 1,453–2,786 meV, being smaller as the flexible sequence in the diamine moieties is longer. The novelty of this work consists in relating optical properties with morphological aspects, namely surface defects and entropy of morphology. These new results have a great impact in selecting the proper materials as liquid crystal alignment layers or as cell culture substrates.

Statistical analysis on morphology development of some semialicyclic polyimides using atomic force microscopy

The morphological features and surface texture parameters of some polyimide films prepared from a flexible and alicyclic dianhydride, in combination with five aromatic diamines, were evaluated by atomic force microscopy (AFM) in order to determine their applicability in electronics. By means of the surface roughness, shape of the surface height distribution, and angular and radial texture, a precise description of the actual surface topographies at the interface with other materials was made. The polyimide structures led to the development of different surface morphologies (from granular to porous and from bumpy to spiky). The relief diversity was described by the entropy of morphology, which had a similar trend with the root mean square roughness, which presents low values, i.e. 0.5-1.8 nm. Three-dimensional AFM images and the corresponding angular spectra, together with texture aspect ratio and texture direction index (close to 1), indicate that no predominant orientation exists on the investigated surfaces. The redundancy in the morphology was associated with the concept of fractals, the maximum redundancy being achieved for the polyimide with the most complex polymer chain conformation. These results provide useful insights in selecting the polyimide structure, which has the optimal morphology, roughness, orientation, bearing properties, or self-similarity for microelectronic applications such as: substrate for display backplanes, planar technology, microelectronic packaging, etc.

Organosoluble semi-alicyclic polyimides derived from 3,4-dicarboxy-1,2,3,4-tetrahydro-6-tert-butyl-1-naphthalene succinic dianhydride and aromatic diamines: Synthesis, characterization and thermal degradation investigation

Semi-alicyclic polyimides (PI-1–PI-4) have been prepared from a newly-developed alicyclic dianhydride, 3,4-dicarboxy-1,2,3,4-tetrahydro-6-tert-butyl-1-naphthalene succinic dianhydride (TTDA) and various aromatic diamines. The asymmetrical alicyclic tetralin structure in TTDA endowed the derived PI resins good solubility in various organic solvents. They were soluble not only in polar aprotic solvents but also in solvents with low boiling points including dichloromethane and tetrahydrofuran. Flexible and tough PI films were successfully cast from their N-methyl-2-pyrrolidone (NMP) solution except PI-1 derived from TTDA and 4,4′-oxydianiline (ODA). The PI films exhibited good optical transparency in the ultraviolet and visible light region with optical transmittances around 80% at a wavelength of 400nm. The PI films showed good thermal stability up to 400°C in nitrogen, after that they thermally decomposed rapidly. The thermal degradation behaviors of the PIs were investigated by means of thermogravimetric analysis-mass spectrometry (TG-MS), thermogravimetric analysis-Fourier transform infrared spectrometry (TG-FTIR) and the real time FTIR spectra (RT-FTIR) analysis techniques. The results revealed that the decomposition of PI-1 (as a representative) took place mainly in the range of 450–550°C. The major degradative fragments at 500°C were clearly identified as the tert-butyl-substituted tetralin moiety and its dealkylation products. Therefore, it can be deduced that for the TTDA-PIs, the single bond bridge attached the maleic anhydride and tetralin anhydride units in TTDA moiety might break first during the heating; thus producing the tetralin fragments.

The impact of rubbing fabric type on surface roughness and tribological properties of some semi-alicyclic polyimides evaluated from atomic force measurements

The morphology of some polyimides (PI) prepared from a flexible and alicyclic dianhydride, in combination with aromatic diamines was investigated in detail before and after rubbing with two types of fabric: cotton velvet (CV) and cellulose diacetate velvet (CDV). Atomic force microscopy was employed to evaluate the correlation between rubbing-induced grooves in PI film and size/flexibility of textile fibers. For both samples surface isotropy decreased appreciatively with 91% after patterning since the appearance of ordered nanostructures in the direction of rubbing. The angular spectra reveal the generation of a surface anisotropy after rubbing process and a higher surface regularity and uniformity when using CV. This result is confirmed by decrease of texture direction index with 75% and of surface texture aspect ratio with 89%. These parameters together with the rubbing fiber characteristics are key factors in controlling liquid crystal alignment on patterned PI surfaces.

Synthesis and properties of multi-block semi-alicyclic polyimides for thermally stable transparent and low CTE film

Highly transparent polyimide (PI) with a low coefficient of thermal expansion (CTE), comparable to that of copper foil (17 ppm/K), has been developed in conjunction with a relatively rigid and symmetrical monomer, trans-cyclohexyl diamine (CHDA), and in so doing we clarified the effectiveness of a multi-block copolymer system in terms of maximizing the degree of CTE reduction as well as mechanical strength without sacrificing other PI film properties such as high thermal stability (Tg > 280 °C) or high transparency. Multi-block co-PIs were synthesized through the formation of end-functional oligomers, anhydride-terminated oligo-imides (OIs), and amine-terminated oligo(amic acid)s (OAAs). Although there is a large polarity difference between OI and OAA, the multi-block copolymerization still took place well enough to produce a highly transparent PI film as well as a clear PI precursor solution. For comparison, random co-PIs and homo-PIs derived from the same monomer species were synthesized. We found that the difference in the polymer sequence – block vs. random – influenced the film properties so that even the respective PIs had the same monomer composition. Multi-block co-PIs effectively decreased CTE with less CHDA content, and marked the highest tensile modulus (Et: 5.1 GPa) and tensile strength (σt: 208 MPa) which surpassed that of homo-PIs. This can probably be attributed to the micro-aggregation for the multi-block system. It is also suggested that they have a close relationship between the micro-aggregation and the cut-off wavelength of the film while keeping a high light transmittance in the visible region.

An insight on the effect of rubbing textile fiber on morphology of some semi-alicyclic polyimides for liquid crystal orientation

Two semi-alicyclic PIs were prepared from bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride (BOCA) and the aromatic diamines: 4,4′-oxydianiline (ODA) or 4-(4-{[4-(4-aminophenoxy)phenyl]sulfonyl}phenoxy)aniline (pBAPS). The obtained films are transparent in visible domain, having a cut-off wavelength of 294 nm for poly(BOCA–ODA) and 264 nm for poly(BOCA– p BAPS), respectively. Atomic force microscopy images indicate a better surface organization after rubbing with cotton velvet (VC) comparatively with cellulose diacetate (VCD). Contact angle measurements reveal a slight increase of hydrophobicity after patterning as a result of dipolar forces intensification and geometrical constraints of the macromolecular chains. The alignment properties of both PIs, tested with N-(4-methoxybenzylidene)-4-butylaniline, are more obviously for processing with VC. Also, the contrast between the dark and bright states is higher for poly(BOCA– p BAPS)/VC comparatively with poly(BOCA–ODA)/VCD, since its larger surface malleability generates deeper microgrooves.

Synthesis and characterization of novel semi-alicyclic polyimides from methyl-substituted tetralin dianhydride and aromatic diamines

The asymmetrical alicyclic dianhydride 3,4-dicarboxy-1,2,3,4-tetrahydro-6-methyl-1-naphthalene succinic dianhydride (MTDA, II) was synthesized from 4-methylstyrene and maleic anhydride under nitric oxide catalysis with a yield >70%. A series of semi-alicyclic polyimides (PIs) (PI–IIa∼PI–IId) were prepared by a one-step high temperature polycondensation procedure from MTDA and various aromatic diamines. For comparison, another series of PIs (PI–Ia∼PI–Id) were prepared from the analogous dianhydride 3,4-dicarboxy-1,2,3,4-tetrahydro-1-naphthalene succinic dianhydride (TDA, I) and the same diamines. The asymmetrical molecular structure of MTDA endowed the derived PIs with good solubilities in common solvents and high optical transparencies in the ultraviolet and visible light regions by decreasing the intramolecular or intermolecular interactions of the polymer chains. The flexible and tough PI films exhibited good thermal stability up to 400 °C and showed glass transition temperatures in the range of 204–271 °C. The PI films exhibited good optical transparency with transmittances >80% at 400 nm, a cut-off wavelength <300 nm and a refractive index <1.54. A series of semi-alicyclic PIs have been synthesized from an alicyclic dianhydride MTDA and various aromatic diamines by a one-step high temperature polycondensation procedure. Flexible and tough PI films have been cast from their solution in common solvents. The PI films exhibited good thermal stability and good transparency in the ultraviolet-visible (UV-vis) light region.

Organosoluble and light-colored fluorinated semialicyclic polyimide derived from 1,2,3,4-cyclobutanetetracarboxylic dianhydride

In this study, the alicyclic dianhydrides 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA) was polymerized with seven kinds of fluorinated aromatic diamines, 2,2′-bis(trifluoromethyl)-4,4′-diaminobiphenyl (1), 1,4-bis(4-amino-2-trifluoromethylphenoxy)benzene (2), 1,4-bis(4-amino-2-trifluoromethylphenoxy)diphenyl (3), 1,4-bis(4-amino-2-trifluoromethylphenoxy) diphenyl ether (4), 2,2-bis[4-(4-amino-2-trifluoromethylphenoxy)phenyl]hexafluoropropane (5), 4,4′-bis(4-amino-2-trifluoromethylphenoxy)diphenyl sulfone (6), and 2,7-bis(4-amino-2-trifluoromethylphenoxy)naphthalene (7), via a two-step polycondensation procedure to prepare seven kinds of fluorinated semialicyclic polyimides (PI) PI-1 ∼ PI-7. The structures of these polyimides were confirmed by infrared spectroscopy (IR). Solubility of the polyimides was tested in various organic solvents and their thermal properties were investigated by dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA). Ultraviolet-visible spectra (UV-vis) and near infrared absorption spectra (NIR) were obtained to evaluate the optical properties of these polyimides. The obtained polyimides PI-1 ∼ PI-7 displayed excellent solubility in a variety of organic solvents; they were readily soluble in amide-type polar solvent. These polyimide films exhibited good optical transparency in the visible light region (400–700 nm) with the transmittance higher than 80% at 450 nm, and these polyimide films showed little absorption at the optocommunication wavelengths of 1.30 and 1.55 μm. These polyimides showed good thermal stability with the 10% thermal decomposing temperatures higher than 443°C in nitrogen and the glass transition temperatures higher than 265°C. In addition, the effect of the structure of fluorinated diamines on the properties of polyimide films was also compared. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Optically Transparent Sulfur-containing Semi-alicyclic Polyimide with High Refractive Index

Abstract Sulfur-containing semi-alicyclic polyimides (PIs) with high refractive indices up to 1.7272 at 632.8 nm have been prepared by the Michael polyaddition of sulfur-containing bismaleimides (SBMIs) with 4,4′-thiobis(benzenethiol) (TBT). These PIs also showed high transparency in the visible region, low birefringence (Δn), and a high glass transition temperature.

Effect of Thermally Treated Talc in Poly(amic acid) and Characterization of the Polyimide Composite Film

An unusual increase in Tg of polyimide composite film consisting of semi-alicyclic polyimide (PI-1) and thermally treated talc (b') was observed by TMA measurement, where the Tg jumped as high as +50 K from the original one with 45 wt% of the baked talc. The degrees of (i) increasing viscosity of the solution with PI-1 precursor and the talc, (ii) increasing Tg of the composite film, and (iii) increasing tensile modulus of the composite film were all corresponded to the amount of thermal weight loss from the original talc. According to XRD and TEM observations, the morphological change of the stacking layer structure inherently talc owns was not occurred while the talc was subjected to bake at 700 °C in nitrogen. Since TG-MS elucidated that the emerged components during the thermal treatment was assignable to carbon dioxide, the original talc included some carbonate impurities. The volume of that contaminant involved in talc thus supposed to be correlation to the film thermal property.

Optically Transparent Sulfur-Containing Polyimide−TiO2 Nanocomposite Films with High Refractive Index and Negative Pattern Formation from Poly(amic acid)−TiO2 Nanocomposite Film

A series of semialicyclic polyimides (PIs) have been successfully prepared by the polycondensation of two alicyclic dianhydrides, 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA) and 1,2,4,5-cyclohexanetetracarboxylic dianhydride (CHDA) with two sulfur-containing aromatic diamines, 4,4′-thiobis[(p-phenylenesulfanyl)aniline] (3SDA) and 2,7-bis(4-aminophenylenesulfanyl)thianthrene (APTT), respectively, by a two-step polymerization procedure via the soluble poly(amic acid) (PAA) precursors. Flexible and tough PI films were obtained with a tensile strength greater than 82 MPa and elongation at breaks higher than 12%. The films showed good thermal and thermal-oxidative stability without significant weight loss up to 400 °C, both in air and nitrogen. The glass-transition temperatures of the PIs ranged from 236.5 to 274.1 °C. Good optical transparency, including the cutoff wavelengths lower than 350 nm and transmittances higher than 80% at 400 nm, was achieved for all the PI films. The refractive indices of the PI films were in the range of 1.6799–1.7130 measured at 632.8 nm, which agreed well with the values calculated by the time-dependent density functional theory (TD-DFT). In addition, PAA-IIa (CHDA-3SDA) showed a good affinity with silica-modified TiO2 nanoparticles. The hybrid system with 45 wt % load of TiO2 nanoparticles, combined with the photobase generator N-{[(4,5-dimethoxy-2-nitrobenzyl)oxy]carbonyl}2,6-dimethylpiperidine (DNCDP) exhibited good photolithographic characteristics. A fine negative pattern with a resolution of approximately 4 µm was successfully printed on the hybrid film. The cured PI-IIa−TiO2 hybrid film exhibited a refractive index of 1.8100 at 632.8 nm.