Thermal Imidization Of Polyamic Acid Research Articles

Low dielectric polyimide microsphere/polyimide composite films based on porous polyimide microsphere

AbstractA low dielectric polyimide/polyimide microsphere (PI/PM) composite film was constructed by thermal imidization of polyamic acid from pyromellitic dianhydride (PMDA) and 4,4′‐oxydianiline (ODA) in the presence of porous PM. The PM particles with particle size of about 2 μm were prepared via the solvothermal method using 3,3′,4,4′‐benzophenonetetracarboxylic dianhydride (BTDA) and ODA as monomers through thermal imidization. Due to the favorable compatibility between the porous PM and PI matrix, the mechanical properties, thermal stability, and dielectric properties of the obtained composite films were significantly improved. The PI/PM composite films had a tensile strength of 44.18–64.32 MPa, and the corresponding elongation at break of 6.21%–11.7%. Furthermore, the thermogravimetric temperatures of T5% were 538.9–563.7°C. The dielectric constants of the composite films at 1 MHz were 2.59–3.68, and the corresponding dielectric loss were only 0.0119–0.00405. Thus, the combination of excellent mechanical properties, high thermal stability, extremely low dielectric constant, and dielectric loss make the composite films ideal for deployment as high‐performance materials for 5G applications.Highlights Low dielectric polyimide composite film was prepared by thermal imidization of polyamic acid in the presence of porous polyimide microspheres. Porous polyimide microspheres were prepared by thermal using the imidization solvothermal method. Low dielectric polyimide composite film with good comprehensive properties.

Analysis of the kinetics of soluble polyimide formation by the thermal imidization of polyamic acids in amide solvents with allowance for the side reaction of anhydride group hydrolysis

Analysis of the kinetics of soluble polyimide formation by the thermal imidization of polyamic acids in amide solvents with allowance for the side reaction of anhydride group hydrolysis

Polyimide-Derived Carbon-Coated Li4Ti5O12 as High-Rate Anode Materials for Lithium Ion Batteries.

Carbon-coated Li4Ti5O12 (LTO) has been prepared using polyimide (PI) as a carbon source via the thermal imidization of polyamic acid (PAA) followed by a carbonization process. In this study, the PI with different structures based on pyromellitic dianhydride (PMDA), 4,4′-oxydianiline (ODA), and p-phenylenediamine (p-PDA) moieties have been synthesized. The effect of the PI structure on the electrochemical performance of the carbon-coated LTO has been investigated. The results indicate that the molecular arrangement of PI can be improved when the rigid p-PDA units are introduced into the PI backbone. The carbons derived from the p-PDA-based PI show a more regular graphite structure with fewer defects and higher conductivity. As a result, the carbon-coated LTO exhibits a better rate performance with a discharge capacity of 137.5 mAh/g at 20 C, which is almost 1.5 times larger than that of bare LTO (94.4 mAh/g).

2D infrared correlation study of the effect of base catalyst on thermal imidization of polyamic acid

The thermally induced structural changes of 6FDA-ODA PAA films in the presence and absence of a base catalyst, 2,6-dimethyl piperidine, were investigated using in situ FTIR spectroscopy. In addition, principal component analysis (PCA) and 2D correlation spectroscopy (2D-COS) were applied to clarify the thermal imidization behaviors. Based on the PCA results, we can confirm the various products formed during thermal imidization. The results of 2D correlation analysis revealed the thermally induced changes in the spectra of the 6FDA-ODA PAA films. In addition, we propose that the thermal imidization of the 6FDA-ODA PAA film in the presence of a base catalyst, 2,6-diemthyl piperidine, starts at a lower temperature than it does in the absence of a base catalyst.

New poly(ether imide)s with pendant di-tert-butyl groups: Synthesis, characterization and gas transport properties

Polymers with bulky substituents are of pronounced interest in membrane based separation applications. In this direction, the present work reports the synthesis and characterization of a series pendant di-tert-butyl and trifluorometyl groups containing new poly(ether imide)s (PEIs). The PEIs were prepared by thermal imidization of polyamic acid which is derived by the reaction of a diamine monomer, namely 1,4-bis-[{2′-trifluoromethyl 4′-(4″-aminophenyl)phenoxy}] 2,5-di-t-butylbenzene (FMTBDA) with four different commercially available aromatic dianhydrides, i.e. BPADA, 6FDA, ODPA, and BTDA. The PEIs are soluble in many organic solvents and show reasonably high intrinsic viscosity (0.87 to 1.10 dL/g in NMP) and weight average molecular mass as high as 371,900 g/mol with a polydispersity index of 3.8. The proton NMR and FTIR spectroscopic investigation are in accordance with the respective polymer repeating unit structures. The physical properties of the polymers like thermal and mechanical stability are investigated thoroughly to assess their suitability for membrane based application. The polymers are thermally stable up to 474 °C with 10% weight loss temperature in air environment and have a glass transition temperature as high as 253 °C. The polymer membranes have satisfactory mechanical strength with stress at break value up to 95 MPa. The gas permeability coefficients of the PEIs are somewhat higher than those of other polyimides prepared from the same dianhydrides.

Correlating the synthesis protocol of aromatic polyimide film with the properties of polyamic acid precursor

Thousands of different copolyimide combinations render it technically impossible to have a single universal synthesis method to produce aromatic polyimide film. This study aimed to outline the selection of synthesis protocol, either through the casting of chemically imidized polyimide solution or thermal imidization of polyamic acid (PAA), to produce the polyimide film. The rheological behaviour, molecular weight, and solubility of five structurally different PAA were analysed and correlated to both imidization methods. In this work, a tough polyimide film was successfully synthesized by casting the chemically imidized polyimide derived from high viscosity (> 81 cP) and high molecular weight (≥ 1.35 x 106 g/mol) PAA. On the contrary, both low viscosity (< 13 cP) and high viscosity (> 81 cP) PAA demonstrated the possibility to produce polyimide film via thermal imidization route. The longer molecular chain of ODPA-6FpDA:DABA (3:2) polyimide produced from thermal imidization had restricted the passage of CO2 across the polyimide film when it was applied in the gas separation application. The outcome from this work serves as a guideline for the selection of suitable polyimide film synthesis protocol, which will minimize the time and chemical consumption in future exploration of new polyimide structure.

Brush‐type surface modification of kapton with a new approach

AbstractIn this study, polystyrene‐ and poly(methyl methacrylate)‐grafted polyimide films were prepared successfully using click chemistry and the ATRP technique. Firstly, kapton films were prepared from stepwise thermal imidization of polyamic acid. Surface modification of kapton films was then achieved by chloromethylation followed by the azide decoration process. For surface grafting of kapton films, polystyrene and poly(methyl methacrylate) as alkyne functional polymers were prepared with alkyne and bromine double functionality using propargyl‐2‐bromopropionate as an initiator. A coupling reaction with azide‐decorated PI surface and alkyne functional polymers was achieved via the Huisgen‐1,3‐dipolar cycloaddition reaction. FTIR spectroscopy, contact angle measurement, thermogravimetry (TG) and differential scanning calorimetry (DSC), energy dispersive X‐ray analysis (EDX) and GPC techniques were used to characterize the grafted polyimides. According to the TG analysis, kapton film was modified at the rate of 8% and 10% with PS and PMMA, respectively.

Structure and properties of polyimide fibers containing benzimidazole and Amide Units

ABSTRACTCo‐polyimide (co‐PI) fibers with outstanding mechanical properties were fabricated via thermal imidization of polyamic acids, derived from a new design of combining the amide and benzimidazole diamine monomers, 4‐amino‐N‐(4‐aminophenyl)benzamide (DABA) and 2‐(4‐aminophenyl)‐5‐aminobenzimidazole (BIA), with 3,3′,4,4′‐biphenyltetracarboxylic dianhydride (BPDA). The crystalline structure and micromorphology of the prepared co‐PI fibers were investigated by synchrotron wide‐angle X‐ray diffraction (WAXD) and small‐angle X‐ray scattering (SAXS). The two‐dimensional WAXD spectra imply that the co‐PI fibers possess a structure between smectic‐like and three‐dimensionally ordered crystalline phase, and all the obtained fibers are highly oriented along the fiber axis. SAXS patterns exhibit a pair of meridional scattering streaks for the homo‐PI (BPDA/BIA) fiber, suggesting the presence of periodic lamellar structure. The incorporation of DABA into the polymer chains destroyed the lamellar structure but led to smaller size of microvoids upon increasing DABA moiety, based on SAXS analysis. The co‐PI fibers, with the molar ratio of BIA/DABA being 7/3, exhibited the optimum tensile strength and modulus of 1.96 and 108.3 GPa, respectively, attributed to the well‐defined ordered and dense structure. The chemical structure and molecular packing significantly affected the thermal stability of fibers, resulting in the different glass transition temperatures (Tg) from 350 to 380 °C. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015, 53, 183–191

Preparation and Application of Polyimide Particles

Aromatic polyimides are considered to be a class of high performance polymers, and they have found a wide range of applications in electronics, aerospace and other industries. They were developed in the 1960s owing to intensive research on heat-resistant polymer. Polyimides in various forms (film, composite matrix, adhesive, plate, etc) were developed now. However, the particle of polyimides were studied only a little until the latter half of the 1990's. Even if polyimides are processed to the particle shape, the particles can be expected to show excellent features. Then, we zealously examined the preparative procedure of polyimide particles, and established the following two methods. (1) Several kinds of polyamic acid particles were prepared using diamines and anhydrous tetracarboxylic acids through precipitation polymerization in organic solvent under ultrasonic irradiation. These polyamic acid particles were heated by about 140-200 °C, and the polyimide particles were obtained. The polyimide particles of an arbitrary size were able to be prepared by this method within the range of submicron order. Moreover, it was also possible to support functional groups to surfaces of the polyimide particles. (2) Polyimide particles of micron order were obtained by heating polyamic acid varnish at about 140-200 °C that induced the thermal imidization of polyamic acids in aproticpolarsolvent. Similarly, it was also possible to support functional groups to surfaces of the polyimide particles by this method.

Multifunctional polyimide/graphene oxide composites via in situ polymerization

ABSTRACTIn this article, we detail an effective way to improve electrical, thermal, and gas barrier properties using a simple processing method for polymer composites. Graphene oxide (GO) prepared with graphite using a modified Hummers method was used as a nanofiller for r‐GO/PI composites by in situ polymerization. PI composites with different loadings of GO were prepared by the thermal imidization of polyamic acid (PAA)/GO. This method greatly improved the electrical properties of the r‐GO/PI composites compared with pure PI due to the electrical percolation networks of reduced graphene oxide within the films. The conductivity of r‐GO/PI composites (30:70 w/w) equaled 1.1 × 101 S m−1, roughly 1014 times that of pure PI and the oxygen transmission rate (OTR, 30:70 w/w) was reduced by about 93%. The Young's modulus of the r‐GO/PI composite film containing 30 wt % GO increased to 4.2 GPa, which was an approximate improvement of 282% compared with pure PI film. The corresponding strength and the elongation at break decreased to 70.0 MPa and 2.2%, respectively. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40177.

Gas Separation Properties of Polyimide Membranes Based on 2,2-Bis(&lt;i&gt;3-amino-4-hydroxyphenyl&lt;/i&gt;)hexafluoropropane

A series of polyimides (PIs) by thermal imidization of polyamic acid (PAA) were prepared in order to investigate the gas separation property. The single gas permeability of He, H2, CO2, O2, N2 and CH4 were measured and compared in order to determine the effect of the reaction content and thermal imidization temperature on the gas separation properties. The results showed that the higher the thermal imidization temperature is, the more beneficial for the gas separation properties of the PI membranes. The optimum polycondensation reaction content on preparing PI was 25 wt%. The highest ideal selectivity of He/CH4, H2/CH4, CO2/CH4 and H2/N2 is 2814.88, 1652.38, 216.63 and 191.58, respectively.

Two Step Synthesis of Hydroxyl Group Polyimide Based on 2,2-Bis(&lt;i&gt;Amino-4-Hydroxyphenyl&lt;/i&gt;)hexafluoropropane

The feasibility of using two step procedures with thermal imidization of polyamic acid (PAA) for synthesizing hydroxyl group polyimide (PI), based on 2,2-Bis(3-amino-4-hydroxyphenyl)hexafluoropropane (Bis-AP-AF), was studied. It was found that a high molecular weight PAA could be successfully synthesized from Bis-AP-AF with 3,3',4,4'-Benzophenone tetracarboxylic dianhydride (BTDA). The optimum polycondensation reaction time on synthesizing molecular weight of the PAA was 4 hours. The PI films could be successfully prepared by thermal imidization of the PAA. The higher the inherent viscosity of the PAA is, the more beneficial for the tensile properties of the PI films. All the results indicate that two step procedures with thermal imidization of the PAA under appropriate conditions represented a promising way for preparation PI films, with a reasonable level of mechanical properties.

Enhanced Thermal Conductivity of Polyimide Films via a Hybrid of Micro- and Nano-Sized Boron Nitride

A new thermally conductive polyimide composite film has been developed. It is based on a dispersion of different particle sizes of boron nitride (BN) in a polyimide (PI) precursor, polyamic acid (PAA). Subsequently, thermal imidization of PAA at 350 degrees C produced the corresponding polyimide composites. 3-Mercaptopropionic acid was used as the surfactant to modify the BN surface for the dispersion of BN in the polymer. The PI/BN composites showed different thermal conductivities at different proportion of BN particle sizes and contents. The thermal conductivity of the PI/BN composite was up to 1.2 W/m-k, for a mixture containing 30 wt % of micro and nanosized BN fillers in the polyimide matrix. The PI/BN composites had excellent thermal properties. Their glass transition temperatures were above 360 degrees C, and thermal decomposition temperatures were over 536 degrees C.

Preparation and properties of aromatic polyimides based on 4,4?-(2,2,2-trifluoro-1-phenylethylidene)diphthalic anhydride

Aromatic polyimides were synthesized from aromatic carboxylic acid dianhydrides, 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA), 4,4′-(2,2,2-trifluoro-1-phenylethylidene)diphthalic anhydride (3FDA), and pyromellitic dianhydride (PMDA), with four typical aromatic diamines. These included polyimide (PI) from 2,2-bis(4-aminophenyl)hexafluoropropane (4BDAP) by two-step procedures; amidation to polyamic acid (PAA), followed by thermal imidization of PAA. The chemical and physical properties of the newly prepared polyimides were compared in terms of their chemical structures, inherent viscosity, thermal property, transmission, dielectric constant, UV cutoff, water absorption, and refractive index. PIs 3FDA/4BDAP and 6FDA/4BDAP were soluble in common organic solvents, whereas others were not. In particular, it was found that the solubility was dependent on the temperature of imidization. The chemical and physical properties of the newly prepared polyimides derived from 3FDA were similar to the polyimides derived from 6FDA. The solubility of polyimide containing an ether functional group in the dianhydride moiety was better than that of the ether functional group in the diamine moiety. The polymers with ether linkage in dianhydride moiety exhibited lower glass transition temperature than their functionality-reversed analogous polymers with ether linkage in diamine moiety. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 38–44, 2002

Preparation and properties of soluble aromatic polyetherimides based on 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]hexafluoropropane dianhydride

Aromatic polyetherimides were synthesized from a fluorine containing aromatic carboxylic acid dianhydride, 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]hexafluoropropane dianhydride (6F-BABPA) and five typical aromatic diamines including 1,1-bis(4-aminophenyl)-1-phenyl-2,2,2-trifluoroethane (3F-DAM) by two-step procedures—amidation to polyamic acids (PAA), followed by thermal imidization of PAA. The chemical and physical properties of the newly prepared polyetherimides (PEI) were compared in terms of their chemical structures, inherent viscosities, mechanical, and thermal properties. All polyetherimides were well soluble in common organic solvents such as N-methyl-2-pyrolidone (NMP), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), pyridine, and methylene chloride. A PEI prepared from 6F-BABPA/3F-DAM was especially easily dissolved in NMP. The glass transition temperature (Tg) range of the obtained PEI was 209–257°C. The dielectric constants and refractive index were 2.8–3.2 and 1.61–1.56, respectively. The polyetherimide, 6F-BABPA/BAPP, with a low fluorine content (11.4% fluorine content), has 0.99% water absorption, whereas the polyetherimide, 6F-BABPA/4-BDAP, having a high fluorine content (26.0% fluorine content) showed 0.35% of water absorption. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 249–257, 2000

Structure and Properties of Novel Asymmetric Biphenyl Type Polyimides. Homo- and Copolymers and Blends

Asymmetric biphenyl type polyimides (PI) were prepared by thermal imidization of polyamic acids (PAA) derived from 2,3,3‘,4‘-biphenyltetracarboxylic dianhydride (a-BPDA) and p-phenylenediamine (PDA) or 4,4‘-oxydianiline (ODA). The dynamic mechanical properties of these PIs were compared with those of the isomeric PIs derived from symmetric 3,4,3‘,4‘-biphenyltetracarboxylic dianhydride (s-BPDA). a-BPDA/PDA polyimide has a considerably bent chain structure compared to semirigid s-BPDA/PDA. Nevertheless, the a-BPDA/PDA film annealed at 350 °C showed a higher Tg than the s-BPDA/PDA film prepared under the same conditions. When these PIs were annealed at 400 °C, a-BPDA/PDA exhibited an abrupt E‘ decrease at the Tg (=410 °C) as well as the counterpart annealed at 350 °C, whereas s-BPDA/PDA showed no distinct Tg in the E‘ curve. Similar annealing effects were also observed for the ODA systems. The unexpectedly higher Tg's of a-BPDA-based PIs could be explained in terms of the more restricted conformational chang...

Carbonization of Spherulitic Aromatic Polyimide Particles

New carbon fine particles were prepared by heat-treatment of highly crystalline polyimide particles at above 1000°C. Such particles were obtained as the result of thermal imidization of polyamic acids in N-methyl-2-pyrrolidon. Thermal decomposition of polyimide particles started from about 500°C and almost finished until 1000°C in a yield of 50%. The morphologies of carbon particles obtained were unique like a whisker or coral with the particle size from 1 to 5μm, judging from the observation of SEM. The polyimide particles kept such unique morphologies throughout their decomposition and carbonization processes. By the treatment at 2800°C, carbon particles were found to be almost graphitized from the observation by TEM or electron diffraction patterns that showed the stacking of graphite layers.

Carbonization of spherulitic aromatic polyimide particles

New carbon fine particles were prepared by heat-treatment of highly crystalline polyimide particles at above 1000°C. Such particles were obtained as the result of thermal imidization of polyamic acids in N-methyl-2-pyrrolidon. Thermal decomposition of polyimide particles started from about 500°C and almost finished until 1000°C in a yield of 50%. The morphologies of carbon particles obtained were unique like a whisker or coral with the particle size from 1 to 5μm, judging from the observation of SEM. The polyimide particles kept such unique morphologies throughout their decomposition and carbonization processes. By the treatment at 2800°C, carbon particles were found to be almost graphitized from the observation by TEM or electron diffraction patterns that showed the stacking of graphite layers.

Highly Crystalline Polyimide Particles

Several kinds of highly crystalline polyimide particles were obtained by heating polyamic acid solutions at 180°C that induced the thermal imidization of polyamic acids in N-methyl-2-pyrrolidone (NMP). The morphology of the particles was a sheaf or coral type that was similar to a polymer spherulite. The WAXD analysis revealed that the particles were highly crystalline. The size of the particles was in the range from 1 μm to 10 μm. It was concluded from the electron diffraction studies that the molecular axis of polyimide in the (PMDA/PPD) particle lay perpendicular to the sheaf surface.

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

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