Tailoring substrate adhesion via flexible chain architecture design in benzoheterocycle polyimide protective coatings

A new diamine monomer 2,2-bis[4-(3-aminophenoxy)phenyl]propane (3-BAPOPP) was synthesized through two steps and its melting point was determined by differential scanning calorimetry (DSC). It was then copolymerized with 4,4′-oxydianiline (44ODA) and 4,4′-oxydiphthalic anhydride (ODPA) to obtain a series of aromatic polyimide(3-BAPOPP/44ODA/ODPA-PI) films. Fourier transform infrared (FT-IR) was used to characterize the structures of the monomer and the polyimide films. Water absorption, ultraviolet-visible (UV-Vis) spectroscopy, contact angle, DSC, and thermo-gravimetric analysis (TGA) were used to characterize the properties of 3-BAPOPP/44ODA/ODPA-P films. The results showed that the PI films had low water absorption in the range of 1.5%∼1.9%, low surface energy in the range of 43.3 ∼43.5 mJ/m2, glass transition temperature (Tg) in the range of 192.5°C∼226.1°C, and dielectric constant in the range of 2.79∼3.02 at 1 MHz. The films also exhibited good thermal properties and good optical properties, with the ultra violet cut-off wavelength being in the range of 346∼364 nm.

Comparative investigations on the effects of pendent trifluoromethyl group to the properties of the polyimides containing diphenyl-substituted cyclopentyl Cardo-structure

In this study, a novel diamine monomer containing ester and phenyl moieties, 1,2-diphenylethane-1,2-diyl bis(4-aminobenzoate) (1,2-DPEDBA), was synthesized through a three-step reaction. Using this diamine, a novel polyimide (PI) film was prepared with 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6-FDA) as a counter dianhydride through a typical two-step chemical imidization. For comparison, poly(pyromellitic dianhydride-co-4,4′-oxydianiline) (PMDA-ODA PI) was also synthesized via thermal imidization. The resulting 6-FDA-DPEDBA PI film was not only soluble in common polar solvents with high boiling points, such as N,N-dimethylacetamide (DMAc) and N,N-dimethylformamide (DMF), but also soluble in common low-boiling-point polar solvents, such as chloroform (CHCl3) and dichloromethane (CH2Cl2), at room temperature. The resulting novel PI showed a 5% weight loss temperature (T5d) at 360 °C under a nitrogen atmosphere. The resulting PI film was colorless and transparent with a transmittance of 87.1% in the visible light region ranging from 400 to 760 nm. The water absorption of the novel PI film was of 1.78%. The PI film also possessed a good moisture barrier and hydrophobicity. Furthermore, the resulting PI film displayed a low dielectric constant of 2.17 at 106 Hz at room temperature. In conclusion, the novel PI film exhibited much better optical transparency, lower moisture absorption, and a lower dielectric constant as well as better solubility than the PMDA-ODA PI film, which is insoluble in any solvent, although its thermal stability is not better than that of PMDA-ODA PI.

Utilization of biodegradable metals in biomedical fields is emerging because it avoids high-risk and uneconomic secondary surgeries for removing implantable devices. Mg and its alloys are considered optimum materials for biodegradable implantable devices because of their high biocompatibility; however, their excessive and uncontrollable biodegradation is a difficult challenge to overcome. Here, we present a novel method of inhibiting Mg biodegradation by utilizing reduced nicotinamide adenine dinucleotide (NADH), an endogenous cofactor present in all living cells. Incorporating NADH significantly increases Mg corrosion resistance by promoting the formation of thick and dense protective layers. The unique mechanism by which NADH enables corrosion inhibition was discovered by combined microscopic and spectroscopic analyses. NADH is initially self-adsorbed onto the surface of Mg oxide layers, preventing Cl− ions from dissolving Mg oxides, and later recruits Ca2+ ions to form stable Ca-P protective layers. Furthermore, stability of NADH as a corrosion inhibitor of Mg under physiological conditions were confirmed using cell tests. Moreover, excellent cell adhesion and viability to Mg treated with NADH shows the feasibility of introduction of NADH to Mg-based implantable system. Our strategy using NADH suggests an interesting new way of delaying the degradation of Mg and demonstrates potential roles for biomolecules in the engineering the biodegradability of metals.

Polyimide (PI) film with hydrophilic greatly limits their application in the field of microelectronic device packaging. A novel hydrophobic PI film with sag structure and improved mechanical properties is prepared relying on the reaction between anhydride-terminated isocyanate-based polyimide (PIY) containing a seven-membered ring structure and the amino-terminated polyamide acid (PAA) via multi-hybrid strategy, this work named it as hybrid PI film and marked it as PI-PIY-X. PI-PIY-30 showed excellent hydrophobic properties, and the water contact angle could reach to 102°, which is 20% and 55% higher than simply PI film and PIY film, respectively. The water absorption is only 1.02%, with a decrease of 49% and 53% compared with PI and PIY. Due to that the degradation of seven-membered ring and generation of carbon dioxide led to the formation of sag structure, the size of sag structures is ≈16.84 and 534.55nm for in-plane and out-plane direction, which are observed on surface of PI-PIY-30. Meanwhile, PI-PIY-30 possessed improved mechanical properties, and the tensile strength is 109.08MPa, with 5% and more than 56% higher than that of pure PI and PIY film, showing greatly application prospects in the field of integrated circuit.

A strategy to construct low temperature curable copolyimides with pyrimidine based diamine

Absrract CuNi90/10 has been used for many decades as a corrosion resistant alloy for seawater applications. Its corrosion resistance mainly results from the formation of a stable, thin and very adhesive protective layer that forms in contact with seawater. The formation of this protective layer can take up to several weeks depending on environmental influences such as temperature, oxygen content or pH value. There is a delay in the formation of a natural protective layer particularly in the case of brackish water. During this time the material is susceptible to corrosion. For this reason, efforts are made to accelerate the process of protective film formation. A typical method is to introduce inhibition with Sodium Diethyl Dithiocarbamate (SDD). Due to its environmentally damaging impact, this method of inhibition and the resulting disposal obligations is a very expensive process. Therefore the formation of a protective layer under naturally occurring conditions and the conditions under inhibition using SDD is being investigated. The goal was to compare both types of protective film formation and estimate whether inhibition with SDD has advantages in corrosion resistance of CuNi90/10 compared to a natural protective film in water from the Weser river.

The synthesis of new A 2 X-type difluoride monomer, N-2-pyridyl-4',4-bis-(4-fluorobenzenesulfonyl)-o-terphenyl-3,6-dimethyl-4,5-dicarboxylic imide (3), is described. The monomer 3 was incorporated into a series of copoly(aryl ether sulfone)s by polymerization of 4,4'-isopropylidenediphenol and 4,4'-difluorophenylsulfone. The incorporation of monomer 3 had an observable effect on both the glass-transition temperature of poly(aryl ether sulfone)s and the tendency for macrocyclic oligomers to form during polymerization. Replacement of the pyridyl imide group via a transimidization reaction with propargyl amine proceeded quantitatively and without polymer degradation. The acetylene containing copoly(aryl ether sulfone) could be crosslinked by simple thermal treatment, resulting in an increase in the glass-transition temperature and solvent resistance.

Aromatic polyimides (PIs) with a hexaphenylbenzene unit were synthesized from 1,4-bis[4-(4-aminophenoxy)phenyl]-2,3,5,6-tetraphenylbenzene (1) and various tetracarboxylic dianhydrides by a conventional two-step procedure that included ring-opening polymerization in N-methyl-2-pyrrolidone and subsequent thermal cyclic dehydration. The PIs were characterized by X-ray diffraction, differential scanning calorimetry, thermogravimetry, and dynamic mechanical analysis. The PIs had glass transition temperatures in the range of 289–352°C, and all the polymers were amorphous. The structure–property relationships of these PIs were examined and compared with those of the previously prepared analogous PIs from 4,4′-bis(4-aminophenoxy)biphenyl (2) and 4,4′-bis(4-amino-2-phenylphenoxy)biphenyl (3). Water absorption and dielectric constants of the PIs were also compared and discussed on the basis of imide content per repeating unit.

With the advantages of excellent physical, chemical and thermal properties, polyimide (PI) film has been widely used as insulation material in electrical and mechanical equipment. However, PI presents water absorption capacity because of the existence of carbonyl and amine groups in the molecular chain. When exposed in moisture conditions, PI film will be degraded. Therefore, the dielectric breakdown occurs and irremediable damage will appear in insulation system. The dielectric properties of PI film are largely influenced by the absorbed water and humidity. Direct fluorination is an effective method of surface modification which can improve the properties of original material from many respects, such as the wettability, barrier properties and chemical stability. In this paper, to study effects of fluorination on dielectric properties of moistened PI films, the PI specimens were surface fluorinated for 15, 30, 45 and 60 min respectively. The specimens without fluorination were also prepared for the contrast. Then the specimens were immersed in high purity water for 6, 12 and 24 hours. The water absorption, permittivity and breakdown strength under different fluorination and immersion time were measured. Meanwhile, given that the existence of surface charge had a critical influence on the breakdown characteristics, the corona charging tests were conducted at room temperature and the charge dissipation was investigated. Obtained results show that fluorination can reduce the water intake capacity and enhance the breakdown strength of PI in moisture conditions. The decay process of surface charge and the change of detrapping charges in PI films are affected by both the fluorination and the immersion time.

Unsaturated polyester resin (UPR) is one of the film-forming resins commonly used for preparation of coatings. However, the general type UPR has some disadvantages which limit its application such as poor water resistance, solvent resistance, heat resistance and mechanical properties. To improve common UPR’s comprehensive performance, methyl-α-eleostearate-maleic anhydride adduct (MEMAA), a derivative from Tung oil, was prepared and introduced into UPR system to form MEMAA modified UPR (M-UPR). Influences of MEMAA’s dosage in M-UPR on water and toluene absorption and tensile strength of M-UPR were investigated. The thermal property and morphology of M-UPR were also studied by TGA and SEM, respectively. Experimental results show that the water resistance, solvent resistance and tensile strength of UPR have been improved a lot and the heat resistance of UPR also has a certain degree of improvement after UPR’ being modified by MEMAA. Compared with the common UPR film, when the dosage of MEMAA is 9% of UPR’s mass, the water absorption, toluene absorption of M-UPR film are decreased by 21.0% and 18.6%, respectively, and whereas, the tensile strength and thermal decomposition temperature of UPR film are increases by 14% and 20 oC.

Semi‐alicyclic colorless and transparent polyimide (PI) films with intrinsically flame‐retardant features, excellent optical transparency, and good thermal stability have been designed and successfully prepared. For this target, an aromatic diamine with lateral diphenylphosphine oxide substituent, 2,5‐bis[(4‐aminophenoxy)phenyl]diphenylphosphine oxide (BADPO) was polymerized with two alicyclic dianhydrides, including hydrogenated pyromellitic dianhydride (HPMDA) and hydrogenated 3,3′,4,4′‐biphenyltetracarboxylic dianhydride (HBPDA), respectively, via a one‐step high‐temperature polycondensation procedure to afford two PIs, PI‐a (HPMDA‐BADPO), and PI‐b (HBPDA‐BADPO). The derived PI films maintained the intrinsic good properties for semi‐alicyclic PI films, including excellent optical transparency in the ultraviolet–visible light region with the cutoff wavelength (λcut) around 322 nm and optical transmittance at the wavelength of 450 nm (T450) higher than 83.0%. In addition, the PI films exhibited good thermal stability with the 5% weight loss temperatures (T5%) higher than 460.0°C and glass transition temperatures (Tg) higher than 235.0°C. More importantly, the developed PI films exhibited intrinsic flame retardancy with the limited oxygen indices (LOI) of 41.1% for PI‐a and 28.8% for PI‐b. What is more, the PI films showed the flame retardancy class of UL94 VTM‐0 and low thermal energy and smoke release during combustion.

Optically transparent polyimide (PI) films with good atomic oxygen (AO) resistance have been paid extensive attention as thermal controls, optical substrates for solar cells or other components for low Earth orbit (LEO) space applications. However, for common PI films, it is usually quite difficult to achieve both high optical transparency and AO resistance and maintain the intrinsic thermal stability of the PI films at the same time. In the current work, we aimed to achieve the target by using the copolymerization methodology using the fluorinated dianhydride 9,9-bis(trifluoromethyl)xanthene-2,3,6,7-tetracarboxylic dianhydride (6FCDA), the fluorinated diamine 2,2-bis [4-(4-aminophenoxy)phenyl]hexafluoropropane (BDAF) and the polyhedral oligomeric silsesquioxane (POSS)-containing diamine N-[(heptaisobutyl-POSS)propyl]-3,5-diaminobenzamide (DABA-POSS) as the starting materials. The fluoro-containing monomers were used to endow the PI films with good optical and thermal properties, while the silicon-containing monomer was used to improve the AO resistance of the afforded PI films. Thus, the 6FCDA-based PI copolymers, including 6FCPI-1, 6FCPI-2 and 6FCPI-3, were prepared using a two-step chemical imidization procedure, respectively. For comparison, the analogous PIs, including 6FPI-1, 6FPI-2 and 6FPI-3, were correspondingly developed according to the same procedure except that 6FCDA was replaced by 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA). Two referenced PI homopolymers were prepared from BDAF and 6FDA (PI-ref1) and 6FCDA (PI-ref2), respectively. The experimental results indicated that a good balance among thermal stability, optical transparency, and AO resistance was achieved by the 6FCDA-PI films. For example, the 6FCDA-PI films exhibited good thermal stability with glass transition temperatures (Tg) up to 297.3 °C, good optical transparency with an optical transmittance at a wavelength of 450 nm (T450) higher than 62% and good AO resistance with the erosion yield (Ey) as low as 1.7 × 10-25 cm3/atom at an AO irradiation fluence of 5.0 × 1020 atoms/cm2. The developed 6FCDA-PI films might find various applications in aerospace as solar sails, thermal control blankets, optical components and other functional materials.

A series of ester‐ and fluoro‐containing thermoplastic polyimide (PI) films, PEsI‐1 ~ PEsI‐4 have been prepared by the two‐step thermal imidization procedure via the soluble poly(amic acid) (PEsAA) precursors from the copolymerization of four monomers, including the dianhydrides of bisphenol A dibenzoate‐3,3′,4,4′‐tetracarboxylic acid dianhydride (TMBPA) and 3,3′, 4,4′‐biphenyl tetracarboxylic acid dianhydride (BPDA) and the diamine monomers of 4‐aminophenyl‐4′‐ aminobenzoate (APAB) and 2,2′‐bis(trifluoromethyl)‐4,4′‐diamino biphenyl (TFMB) in the polar aprotic solvent of N‐methyl‐2‐pyrrolidinone (NMP). The PI films obtained from the high‐temperature dehydration of the PEsAA solutions exhibited the good thermal stabilities with the glass transition temperatures (Tg) over 269°C, the 5% weight loss temperatures (T5%) higher than 480°C, and the linear coefficients of thermal expansion (CTE) values in the range of 17.7 × 10−6/K–33.6 × 10−6/K in the temperature range of 50–250°C. Meanwhile, the PI films showed good thermoplasticity in the dynamic mechanical analysis (DMA) tests, in which the storage modulus of the PI films dropped sharply in the temperature range of glass transition of the polymers. At last, the PI films exhibited the good dielectric properties with the breakdown voltages (Vb) over 5200 V, the dielectric strength (Ds) higher than 210 V/μm, the dielectric constants (Dk) in the range of 3.26 ~ 3.32 at the frequency of 10 GHz, and the dielectric dissipation factors (Df) of 0.0038 ~ 0.0047. Compared with the commonly used PEsI‐ref film for high‐frequency flexible copper clad laminates (FCCL), the currently developed PI films exhibited the obviously increased Tg values, decreased CTE values, and comparable dielectric properties.

Sorption and permeation of CO2 in various annealed polyimide (PI) films were investigated. Dual‐mode sorption and partial immobilization models were used to analyze the data. Sorption of CO2 in PI film quenched from above the glass transition temperature (Tg) is greater than in film as received. In fact, sorption is decreased over the entire pressure range by cooling the film slowly. These changes in sorption of CO2 can be attributed to a change in the Langmuir sorption capacity C′H by annealing, since the other dual‐mode sorption parameters, kD and b, are almost independent of annealing. The value of C′H is increased by quenching, and decreased by slow cooling from above Tg. The two diffusion coefficients DD and DH according to the Henry and Langmuir modes, respectively, for CO2 also depend markedly on annealing. Diffusion coefficients of quenched PI films are increased and those of film cooled slowly are decreased compared with values for PI film as received. The change in DH is larger than that in DD. The permeability coefficient of quenched PI films at 100 cmHg is about 1.7 times that of PI film as received. The film structure formed by quenching can enhance permselectivity.