Oxydiphthalic Anhydride Research Articles

Based on rigid xanthone group and hydrogen bonding to construct polyimide films with low coefficient of thermal expansion, high temperature resistance, and fluorescent property

In recent years, an increasing amount of attention has been paid to polyimide (PI) substrate materials with high glass transition temperature (Tg) and low coefficient of thermal expansion (CTE) due to the rapid development of the flexible OLED field. To improve Tg and CTE, rigid conjugated structure and hydrogen bonds are designed. Two diamines containing amide and rigid xanthone groups were synthesized (p-DAXBA and m-DAXBA). Two series of PI films, PIa and PIb, were prepared by polymerization of DAXBA with different dianhydrides, i.e., pyromellitic dianhydride (PMDA), 3,3′,4,4′-biphenyl tetracarboxylic diandhydride (BPDA), 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), and 4,4′-oxydiphthalic anhydride (ODPA). PIa films prepared by p-DAXBA have more hydrogen bonding, closer molecular chain packing, and stronger molecular charge transfer (CT) effect, as well as better heat resistance, dimensional stability, and mechanical properties than PIb films prepared by m-DAXBA. However, their absolute fluorescence quantum efficiency and transparency are weaker than those of PIb films. A PIa-1 film prepared by p-DAXBA/PMDA has a Tg of 400 °C, tensile strength of 192 MPa, modulus of 6.14 GPa, and CTE as low as 2.3 ppm·K−1. Both PIa-4 and PIb-4 films prepared by ODPA show fluorescent property with maximum emission wavelengths at 509 and 508 nm, and their absolute fluorescence quantum efficiencies are 1.5% and 2.9%, respectively. The as-prepared PI films exhibit potential application in the flexible OLED field.

Mechanically Tough and Durable Poly(siloxane imide) Network Elastomer for Stretchable Electronic Applications

In the development of organic electronics, polyimide (PI)-based materials have drawn significant research attention due to their remarkable features, including a simple synthesis, solution processability, outstanding thermal stability, and respectable mechanical strength. Despite the good electronic performance of PI-based materials, a high elastic modulus over 1 GPa and a modest elongation at break of the conventional PIs have restricted their applications in stretchable electronics. To address this issue, poly(siloxane imide) (PSI) with a soft siloxane chain has been proposed to achieve a significantly reduced modulus and an increased stretchability. However, previous works revealed the weak mechanical strength of PSI, in which the latest reported stretchable device comprising PSI thin film could only sustain a tensile strain below 40%. Herein, in the present study, we developed a thermally stable and mechanically durable PSI network through the polyaddition–condensation reaction between 4,4′-oxidiphthalic anhydride, aminopropyl-terminated polydimethylsiloxane, and varied amounts of 1,3,5-triaminophenoxybenzene (TAB) as a cross-linker. An optimal PSI network with 11.1% TAB exhibited a high decomposition temperature at 426 °C, a softening temperature over 200 °C, an elongation at break over 400%, a superior toughness at 13.29 MJ m–3, and low strain hysteresis. Owing to the improved solubility of PSI, the polymer elastomer can be processed as a substrate material or thin-film active layer with good mechanical properties. Finally, all-solution-processed, stretchable, and durable electronic devices including resistive memory and organic field-effect transistors were fabricated using the designed PSI with an affordable and feasible solution process. This work underlines the importance of network design on soft polymers to create mechanically tough and durable elastomers for next-generation stretchable electronics.

Preparation and properties of ODPA-ODA-SDA polyimide film and its application in corona resistance

High-frequency trend of electrical equipment puts forward higher requirements on the dielectric properties of insulating materials, especially under corona ageing environment. Therefore, a facile and effective method for improved corona resistance is essential for the development of high-frequency power systems. In this article, 4,4′-Oxydiphthalic anhydride (ODPA) was chosen as the dianhydride while 4,4′-Diaminodiphenyl ether (ODA) and 4,4′-diaminodiphenyl sulphide (SDA) as diamines. Consequently, thermally imidized ODPA-ODA-SDA copolyimides were synthesized, and the influence of ODPA and SDA on the dielectric properties was discussed. High-frequency corona ageing test was also conducted to investigate the relationship between dielectric properties and the corona resistance. From dielectric frequency spectra analysis, the ODPA-ODA-SDA copolyimide was considered to exhibit the best dielectric properties when SDA accounted for 30% mole fraction of diamine, the dielectric loss of which was 24.03% lower than that of ODPA-ODA at 20 kHz. Meanwhile, the better corona resistance property and mechanical properties were obtained, especially the corona ageing lifetime was 2.26 times higher than that of ODPA-ODA. To further improve the corona resistance property, a series of modified-PI/Al2O3 nanocomposite films based on ODPA-ODA-SDA matrix were prepared by in-situ polymerization. When the content of Al2O3 nanoparticles reached 12 wt%, the thermal stability was improved and the corona ageing lifetime was 6.14 times longer than that of ODPA-ODA. This experiment provides new ideas and directions for reducing mechanical and thermal performance losses as well as achieving high-efficiency corona resistance, which is expected to promote the development of advanced insulating films.

Effect of structural isomerism on physical and gas transport properties of Tröger's Base-based polyimides

The physical and gas transport properties of Tröger's Base (TB)-based polyimides (PI-TBs) synthesized by isomeric monomers were rarely reported. Here, a series of PI-TBs was synthesized from two iso-ether dianhydrides [4,4′-oxydiphthalic anhydride (4,4′-ODPA)/3,4′-oxydiphthalic anhydride (3,4′-ODPA)] and two iso-biphenyl dianhydrides [3,3′,4,4′-biphenyltetracarboxylic dianhydride (4,4′-BPDA)/3,4′-biphthalic anhydride (3,4′-BPDA)], with two diamines, 2,5-dimethyl-1,4-phenylenediamine (DPD) or 2,6-diaminotoluene (DAT). The solubility, microporosity, chain packing, mechanical performance and thermal stability, and gas transport properties were investigated for the PI-TBs derived from the isomeric dianhydrides. The polyimides derived from DPD and appropriate dianhydrides had better solubility and film-forming capability, mechanical properties, and higher gas permeability than those from DAT analogues. Furthermore, the polyimides based on different isomeric dianhydrides showed good solubility, mechanical properties, and high thermal stability and glass transition temperatures (Tgs), up to 400 °C. The chemical structures of isomeric dianhydrides have a noticeable influence on the chain packing and gas separation performance of the PI-TBs. The PI-TBs with rigid 3,4’-/4,4′-BPDA residues showed microporosity and their BET values in the range of 235.2–324.9 m2/g. The PI-TB membranes from the 3,4′-BPDA showed both higher gas permeability and selectivity (H2/CO2, H2/CH4, CO2/CH4) compared to those from the 4,4′-BPDA. On the contrary, the PI-TB membranes from the 3,4′-ODPA had lower gas permeability with improved gas selectivity compared to those from the corresponding 4,4′-ODPA.

Processable poly(ether ether ketone imide)s

New aromatic poly(ether ether ketone imide)s, [PEEKimide]s, were synthesized successfully from 1,3-bis-4′-(4″-aminophenoxy benzoyl) benzene and various commercially available aromatic dianhydrides, such as pyromellitic dianhydride (PMDA), 3,3′,4,4′-benzophenone tetracarboxylic dianhydride (BTDA), 3,3′,4,4′-biphenyl tetracarboxylic dianhydride (BPDA), 4,4′-oxydiphthalic anhydride (OPDA) and 4,4′-(hexafluro isoproylidene) diphthalic anhydride (HFDA), by two step polycondensation method. These PEEKimides were characterized by FT-IR, solubility in organic solvents, inherent viscosity, DSC, TGA and WXRD. Inherent viscosities of the precursor poly(ether ether ketone amic acid)s were in the range of 0.23–0.40 dl/g in DMF, indicating formation of moderate to high molecular weights. These poly(ether ether ketone imide)s showed good solubility in polar aprotic solvents such as N,N-dimethylacetamide (DMAc), N-methyl 2-pyrrolidone (NMP), N,N-dimethylformamide (DMF) and dimethyl sulphoxide (DMSO) and had glass transition temperatures in the range 245–279°C. Poly(ether ether ketone imide)s showed no weight loss below 280°C; temperatures for 10% weight loss (T10) were in the range of 406–483°C and char yields at 800°C were 17–34%, indicating their good thermal stability. All these poly(ether ether ketone imide)s were amorphous in nature, as per patterns of WXRD which exhibited diffuse broad halos at (2θ = 10–30°) and amorphous nature was reflected in polymer’s good solubility in common organic solvents.

Intermolecular Interactions and Intramolecular Motions in Photomechanical Effect: Nonlinear Thermo- and Photomechanical Behaviors of Azobenzene-Functionalized Amide-Imide Block Copolymers.

To discern multiple intertwined effects, a set of azobenzene-functionalized amide-imide block copolymers, azo(PA-co-PI)-x, where x is amide-block content, viz., [azoPA] = 25, 50, 75 mol %, was synthesized from 2,2-bis{4-[4-(4-aminophenyldiazenyl)phenoxy]phenyl}propane(azoBPA), 4,4'-oxydibenzoyl chloride (ODBC), and 4,4'-oxydiphthalic anhydride (OPDA). Including homopolymers (azoPA and azoPI), this series of amorphous azopolymers possesses a high glass-transition temperature (Tg > 210 °C) and a modulus (E' ∼ 1.23-2.50 GPa). Their photobending (ca. 23-90°) and photostress (ca. 250-380 kPa) were assessed in the form of cantilevers with a linearly polarized 445 nm light. Nonlinear composition/[azoPA] dependencies of the thermo- and photomechanical properties are correlated. As [azoPA] increases from 0 mol %; Tg, E', photostress, and photobending angle initially decrease to reach four separate minima for azo(PA-co-PI)-50; and then all increase with a higher [azoPA]. The trend considerations of film density, dynamic thermomechanical, Fourier transform infrared (FT-IR), and ultraviolet-visible (UV-vis) measurements implicate that (i) intermolecular association and intramolecular segmental mobility collectively influence the photomechanical outcomes and (ii) two types of hydrogen bonding (HB), namely, amide-amide [HB-AA] and amide-imide [HB-AI] coexist in azo(PA-co-PI)-x copolymers, with [HB-AI] being largely responsible for photomechanical outcomes of azo(PA-co-PI)-x with [azoPA] <40-50 mol %, and [HB-AA] for [azoPA] >40-50 mol %. We hypothesize that the "U-shaped" photomechanical effect apparently stems from the cooperative "unzipping" of H bonds in the [HB-AA]* excited state with H bonds in [HB-AI]* being stabilized by electrostatic interactions inherent in an excited intermolecular complex.

High-Temperature-Induced Shape Memory Copolyimide.

A series of polyimide (PI) films with a high-temperature-induced shape memory effect and tunable properties were prepared via the facile random copolymerization of 4,4′-oxydianiline (ODA) with 4,4′-(hexafluoroisopropyl)diphthalic anhydride (6FDA) and 4,4′-oxydiphthalic anhydride (ODPA). The trigger temperature can be controlled from 294 to 326 °C by adjusting the ratio of monomers. The effects of monomer rigidity on the chain mobility, physical properties, and shape memory performance of as-prepared copolyimide were systematically investigated. The introduction of ODPA could enhance the mobility of PI macromolecular chains, which made chain entanglement more likely to occur and increased the physical crosslinking density, thereby improving the PI’s shape recovery up to 97%. Meanwhile, the existence of 6FDA enabled PI films to set quickly at low temperatures with a shape fixation of 98%. The shape memory cycling characteristics of the polyimide films are also studied, and the relationship between the PI chemical structure and the film properties are further discussed.

Novel acetylene‐terminated thermosetting polyisoimides with excellent solubility and performed as efficient heat shields composites

AbstractThe acetylene‐terminated polyisoimide oligomers introducing 2,2′‐bis (trifluoromethyl)benzidine (TFMB) or 3,4′‐oxydiphthalic anhydride (3,4′‐ODA) as the diamine were synthesized, and short quartz fiber reinforced polyisoimide composites were prepared. The structure, processability, and thermal properties of polyisoimide oligomers were characterized. The mechanical properties and ablation protection performances of the composites were tested. The effects of TFMB on the processability and thermal properties of polyisoimides were studied. The application properties of short quartz fiber reinforced polyisoimide composites as thermal protection materials were evaluated by coal gas/oxygen ablation test system. These results showed that the introduction of TFMB into the polyisoimide structure can improve its solubility and heat resistance, as well as the ablation protection performances of the composites. The above results showed its potential application in the field of thermal protection materials. This makes it possible for polyisoimide composites to be used in the field of ablation protection.

Effect on the thermal resistance and thermal decomposition properties of thermally cross-linkable polyimide films obtained from a reactive acetylene

Homopolyimides are prepared by 4,4′-(ethyne-1,2-diyl)diphthalic anhydride as dianhydride monomer and several diamine monomers. The copolyimides are prepared with 4,4′-oxydianiline as an amine monomer， 3,3′,4,4′-oxydiphthalic anhydride as an anhydride monomer with the addition of 4,4′-(ethyne-1,2-diyl)diphthalic anhydride as another anhydride monomer. The structure of polyimides is characterized by Fourier transform infrared spectroscopy and X-ray diffraction. Thermogravimetric analysis, thermomechanical analysis and thermo-oxidative degradation kinetics analysis are used to investigate the properties of polyimides. The homopolyimide show the best thermal stability in both nitrogen and air atmosphere by 4,4′-oxydianiline and 4,4′-(ethyne-1,2-diyl)diphthalic anhydride. The results also indicate that the thermally cross-linkable copolyimide films not only enhance the thermal stability behaviors of polyimide by controlling the addition of dianhydride, but also improve substantially the upper limit temperature of thermal aging by undergoing chemical cross-linking reaction of the diphenylethynylene structures and providing multifarious naphthalene ring groups and biphenyl structures. Diphenylacetylene crosslinking merging to the long-chain of polyimide is a useful conversion for enhancing the thermal stability and the thermal degradation stability of aromatic polymers.

Preparation and Properties of Electrospun Phenylethynyl-Terminated Polyimide Nano-Fibrous Membranes with Potential Applications as Solvent-Free and High-Temperature Resistant Adhesives for Harsh Environments.

High-temperature-resistant polymeric adhesives with high servicing temperatures and high adhesion strengths are highly desired in aerospace, aviation, microelectronic and other high-tech areas. The currently used high-temperature resistant polymeric adhesives, such as polyamic acid (PAA), are usually made from the high contents of solvents in the composition, which might cause adhesion failure due to the undesirable voids caused by the evaporation of the solvents. In the current work, electrospun preimidized polyimide (PI) nano-fibrous membranes (NFMs) were proposed to be used as solvent-free or solvent-less adhesives for stainless steel adhesion. In order to enhance the adhesion reliability of the PI NFMs, thermally crosslinkable phenylethynyl end-cappers were incorporated into the PIs derived from 3,3’,4,4’-oxydiphthalic anhydride (ODPA) and 3,3-bis[4-(4-aminophenoxy)phenyl]phthalide (BAPPT). The derived phenylethynyl-terminated PETI-10K and PETI-20K with the controlled molecular weights of 10,000 g mol−1 and 20,000 g mol−1, respectively, showed good solubility in polar aprotic solvents, such as N-methyl-2-pyrrolidinone (NMP) and N,N-dimethylacetamide (DMAc). The PI NFMs were successfully fabricated by electrospinning with the PETI/DMAc solutions. The ultrafine PETI NFMs showed the average fiber diameters (dav) of 627 nm for PETI-10K 695 nm for PETI-20K, respectively. The PETI NFMs showed good thermal resistance, which is reflected in the glass transition temperatures (Tgs) above 270 °C. The PETI NFMs exhibited excellent thermoplasticity at elevated temperatures. The stainless steel adherends were successfully adhered using the PETI NFMs as the adhesives. The PI NFMs provided good adhesion to the stainless steels with the single lap shear strengths (LSS) higher than 20.0 MPa either at room temperature (25 °C) or at an elevated temperature (200 °C).

A Novel Strategy to Enhance the Performance of CO2 Adsorption Separation: Grafting Hyper-cross-linked Polyimide onto Composites of UiO-66-NH2 and GO.

Graphene oxide (GO) is widely used to improve the pore structure, dispersion capacity, adsorption selectivity, resistance to acids and bases, and thermal stability of metal-organic frameworks (MOFs). However, it remains a daunting challenge to enhance selectivity simply by modifying the pore surface polarity and producing a suitable pore structure for CO2 molecules through a combination of GO with MOFs. Herein, we demonstrate a novel porous hyper-cross-linked polyimide-UiO-graphene composite adsorbent for CO2 capture via in situ chemical knitting and condensation reactions. Specifically, a network of polyimides rich in carbonyl and nitrogen atoms with amino terminations was synthesized via the reaction of 4,4'-oxydiphthalic anhydride (ODPA) and 2,4,6-trimethyl-1,3-phenylenediamine (DAM). The product plays a crucial role in the separation of CO2 from N2. As expected, the resulting composite (PI-UiO/GO-1) exhibited a 3-fold higher CO2 capacity (8.24 vs 2.8 mmol·g-1 at 298 K and 30 bar), 4.2 times higher CO2/N2 selectivity (64.71 vs 15.43), and significantly improved acid-base resistance stability compared with those values of pristine UiO-66-NH2. Furthermore, breakthrough experiments verified that the porous composites can effectively separate CO2 from simulated fuel gas (CO2/N2 = 15/85 vol %) with great potential in industrial applications. More importantly, this strategy can be extended to prepare other MOF-based composites. This clearly advances the development of MOF-polymer materials for gas capture.

Polyimide-Based Membrane Materials for CO2 Separation: A Comparison of Segmented and Aromatic (Co)polyimides.

A series of new poly(ethylene oxide) (PEO)-based copolyimides varying in hard segment structure are reported in this work as CO2 selective separation membranes. Their structural diversity was achieved by using different aromatic dianhydrides (4,4′-oxydiphthalic anhydride (ODPA), 4,4’-(hexafluoroisopropylidene)diphthalic anhydride (6FDA)) and diamines (4,4′-oxydianiline (ODA), 4,4′-(4,4′-isopropylidene-diphenyl-1,1′- diyldioxy)dianiline (IPrDA), 2,3,5,6-tetramethyl-1,4-phenylenediamine (4MPD)), while keeping the content of PEO (2000 g/mol) constant (around 50%). To get a better insight into the effects of hard segment structure on gas transport properties, a series of aromatic polyimides with the same chemistry was also studied. Both series of polymers were characterized by 1HNMR, FTIR, WAXD, DSC, TGA, and AFM. Permeabilities for pure He, O2, N2, and CO2 were determined at 6 bar and at 30 °C, and for CO2 for pressures ranging from 1 to 10 bar. The results show that OPDA-ODA-PEO is the most permeable copolyimide, with CO2 permeability of 52 Barrer and CO2/N2 selectivity of 63, in contrast to its fully aromatic analogue, which was the least permeable among polyimides. 6FDA-4MPD-PEO ranks second, with a two times lower CO2 permeability and slightly lower selectivity, although 6FDA-4MPD was over 900 times more permeable than OPDA-ODA. As an explanation, partial filling of hard domain free voids by PEO segments and imperfect phase separation were proposed.

Partially bio-based triarylamine-containing polyimides: Synthesis, characterization and evaluation in non-volatile memory device applications

A new triarylamine-containing diamine, viz. 4, 4′-diamino-4″pentadecyltriphenylamine was synthesised starting from cashew nut shell liquid (CNSL) - a non-edible by-product of cashew processing industry. Three new partially bio-based triarylamine-containing polyimides were synthesised by one-step high temperature solution polycondensation of 4, 4′-diamino-4′'pentadecyltriphenylamine with aromatic dianhydrides, namely, 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA), 4,4′-oxydiphthalic anhydride (ODPA) and 4,4′-(hexafluoroisopropylidene) diphthalic anhydride (6-FDA). Polyimides were determined to be of reasonably high molecular weights as inherent viscosity and number average molecular weights (Mn, Polystyrene standard) values were in the range 0.54–0.60 dL g−1 and 26,800–43,500 g mol−1, respectively. Polyimides exhibited excellent solubility in common organic solvents and film-forming nature along with reasonably good thermal properties as indicated by temperature for 10% weight loss (T10) and glass transition temperatures (Tg) which were in the range 418–447 and 165–225 °C, respectively. The optical and electrochemical band-gap values were in the range of 1.95–1.98 eV and 1.671–1.745 eV, respectively. Among triarylamine-containing polyimide devices, BPDA-based device showed acceptable current-voltage and non-volatile memory properties such as the endurance of 500 cycles and 1000 s of retention time. The conduction mechanism developed in the memory devices was also explored and was found to follow Ohmic and Schottky conduction mechanisms.

Characterization of synthesized new chitin derivatives and Schottky diodes made using these derivatives

In this study, two new chitin derivatives were firstly synthesized. The products formed as a result of the reactions between chitin with 4-bromo-1,8-naphthalic anhydride and 4,4′-oxydiphthalic anhydride were abbreviated as C4B18NA and C44′OA, respectively. The structures of the chitin derivatives were illuminated by various spectroscopic methods (FTIR, NMR, and XRD), and it was thus confirmed that they were synthesized. The surface structures of the chitin derivatives were investigated by SEM technique. Then, two separate diodes were made using aluminum as metal, the chitin derivatives as interfacial layer, and p-Si as semiconductor. Some important properties of the diodes made were determined both in the dark and under an illumination of 100 mW/cm2. It was seen that the diodes are more ideal than most of the diodes where aluminum and p-type silicon were used as metal and semiconductor in their structures, respectively.

Intrinsically heat-sealable polyimide films with atomic oxygen resistance: Synthesis and characterization

Intrinsically heat-sealable polyimides with atomic oxygen (AO) resistance (ARPIs) were synthesized from 2,3,3′,4′-oxydiphthalic anhydride (aODPA), 2,5-bis[(4-aminophenoxy)phenyl]diphenylphosphine oxide (BADPO), and para-phenylenediamine (PDA). The effects of the molecular structure and diamine ratio were investigated on the properties of the ARPI, including mechanical property, thermal property, heat sealability, and AO resistance. Heat sealability and AO resistance were realized for the ARPI film by combining the asymmetry of the aODPA moiety and the passivated layer forming characteristic of diphenylphosphine phosphine oxide group. Meanwhile, the deficiency of low mechanical strength and thermal resistance, commonly existing in a completely BADPO-derived polyimide system, was remedied effectively by the higher reactivity and rigidity of PDA.

Highly Soluble Polyimides Containing Di-tert-butylbenzene and Dimethyl Groups with Good Gas Separation Properties and Optical Transparency

A rigid aromatic diamine monomer containing di-tert-butylbenzene and dimethyl groups, 3,3′-dimethyl-4,4′-diaminophenyl-3″,5″-di-tert-butyltoluene, was successfully synthesized by a simple coupling reaction using 3,5-di-tert-butylbenzaldehyde and o-toluidine as starting materials. A series of novel polyimides (PI 3a–3c) with large pendant groups were prepared with the obtained diamine monomer and three different commercial aromatic dianhydrides (3,3′,4,4′-biphenyltetracarboxylic dianhydride, 4,4′-oxydiphthalic anhydride, and 4,4′-(hexafluoroisopropylidene)diphthalic anhydride) by one-step high temperature polycondensation. The prepared polyimides exhibited high solubility and good membrane forming ability: they could be dissolved not only in some high boiling solvents such as DMF, NMP, DMAc, and m-Cresol at room temperature, but also in some low boiling solvents such as CHCl3, CH2Cl2, and THF. Their solubility in most solvents could exceed 10 wt%, and the flexible membranes could be obtained by casting their solutions. The prepared membranes exhibited good gas separation properties. The permeability coefficients of PI 3c for CO2 and O2 were up to 124.6 and 42.8 barrer, respectively, and the selectivity coefficients for CO2/CH4 and O2/N2 were 14.7 and 3.3, respectively. The membranes had light color and good optical transmission. Their optical transmittance at 450 nm wavelength was in the range of 67%–79%, and the cutoff wavelength was in the range of 310–348 nm. They also had good thermal properties with glass transition temperature (Tg) values in the range of 264–302 °C. In addition, these membranes possessed good mechanical properties with tensile strength ranging between 77.8–87.4 MPa, initial modulus ranging between 1.69–1.82 GPa, and elongation at break ranging between 4.8%–6.1%.

Synthesis and properties of fluorinated copolymerized polyimide films

Two series of fluorinated copolymerized polyimide films with different dianhydride ratios were prepared via the conventional two-step method by using 4,4-oxydianiline(ODA) as the diamine monomer, 4,4'-(hexafluoroisopropylidene) diphthalic anhydride(6FDA), 4,4'-oxydiphthalic anhydride(ODPA) and 3,3',4,4'- biphenyl tetracarboxylic dianhydride(BPDA) as the dianhydride monomer in N, N-dimethylacetamide. With the increase of 6FDA in the proportion of dianhydride, the tensile strength of the polyimide film showed a decreasing trend. This work provided a high performance film. The mass retention rate at 800°C was above 50%. The glass transition temperatures of the two films were 260 °C and 275 °C. The storage modulus of the two were 1500 MPa and 1250 MPa. The loss modulus were 218.70 MPa and 120.74 MPa. The transmittance of the film was 71.43%. The transmittance of fluorinated copolymerized polyimide films were significantly improved in the visible region of ultraviolet light, indicating that the polyimide film with high transmittance, high tensile strength, high heat resistance and high storage modulus was successfully prepared. It had an excellent application prospect in the field of flexible display.

Synthesis and gas permeation properties of thermally rearranged poly(ether-benzoxazole)s with low rearrangement temperatures.

The diamine monomer, 9,9-bis[4-(4-amino-3-hydroxylphenoxy)phenyl] fluorene (bis-AHPPF) was successfully synthesized according to our modified method. A series of hydroxyl-containing poly(ether-imide)s (HPEIs) were prepared by polycondensation of the bis-AHPPF diamine with six kinds of dianhydrides, including 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA), pyromellitic dianhydride (PMDA), 3,3′,4,4′-biphenyl tetracarboxylic diandhydride (BPDA), 3,3′,4,4′-oxydiphthalic anhydride (ODPA), 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA) and 4,4′-(hexafluoroisopropylidine)diphtalic anhydride (6FDA) followed by thermal imidization. The corresponding thermally rearranged (TR) membranes were obtained by solid state thermal treatment at high temperature under a nitrogen atmosphere. The chemical structure, and physical, thermal and mechanical properties of the HPEI precursors were characterized. The effects of heat treatment temperature and dianhydrides on the gas transport properties of the poly(ether-benzoxazole) (PEBO) membranes were also investigated. It was found that these HPEIs showed excellent thermal and mechanical properties. All the HPEI precursors underwent thermal conversion in a N2 atmosphere with low rearrangement temperatures. The gas permeabilities of the PEBO membranes increased with the increase of thermal treatment temperature. When HPEI–6FDA was treated at 450 °C for 1 h, the H2, CO2, O2 and N2 permeabilities of the membrane reached 239.6, 196.04, 46.41 and 9.25 Barrers coupled with a O2/N2 selectivity of 5.02 and a CO2/N2 selectivity of 21.19. In six TR-PEBOs, PEBO–6FDA exhibited the lowest rearrangement temperature and largest gas permeabilities. Therefore, thermally rearranged membranes from bis-AHPPF-based HPEIs are expected to be promising materials for gas separation.

Development of voltammetric sensor based on polyimide-MWCNT composite membrane for rapid and highly sensitive detection of paracetamol

In this work, for low level detection of paracetamol (PA) a voltammetric sensor was obtained. Polyimide-multiwall carbon nanotube (PI-MWCNT) composite film was used for modification of platinum (Pt) electrode as selective membrane. Firstly, this PI-MWCNT film was synthesized with 2,5-diaminopyridine (DAP), 4,4′-oxydiphthalic anhydride (ODPA) and MWCNT as a reinforcement by thermal imidization technique. The morphology, micro and chemical structures of the obtained composite film were studied by Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and thermal analysis techniques. Then, the paracetamol sensor was prepared via the modification of Pt electrode with prepared PI-MWCNT composite film. Pt electrode was modified by coating with prepared PI-MWCNT composite film. Modified Pt electrode was used as PA sensor due to its selective membrane property in the presence of interfering substances for the electrochemical detection of PA. Electrochemical behaviour of paracetamol at the polyimide film modified Pt electrode was obtained by differential pulse voltammetry (DPV) and cyclic voltammetry (CV) method. It has shown that the modified electrode exhibits remarkable repeatability and precision in analytical paracetamol response as compared with other modified paracetamol electrodes. Comparing the responses of modified electrode with the unmodified Pt electrode, selectivity, sensitivity and stable responses significantly enhanced. A linear calibration plot having a correlation coefficient of 0.997 was obtained in the concentration range from 0.3 to 1.8 mM paracetamol. A linear calibration plot for low concentration area having a correlation coefficient of 0.999 was obtained in the concentration range from 0.002 to 0.05 mM paracetamol. Detection limit (LOD) and quantitative limit (LOQ) for paracetamol detection of PI-MWCNT modified electrode were calculated as 0.002 mM and 0.006 mM respectively. In addition, the presented method was applied for determination of PA in commercial tablets. The recovery efficiency of the PI modified electrode was obtained range of 96% and 102% for three different tablets. As a result; a simple, rapid, low cost, repeatable method showing good accuracy and precision (99.4%) has been developed for the selective and sensitive determination of paracetamol by prepared PI-MWCNT composite film modified electrode.

Differential Pulse Voltammetric (DPV) Determination of the Local Anesthetic Bupivacaine using Polyimide Membrane-Based Electrodes

Aromatic selective polyimide (PI) membrane based voltammetric electrodes were prepared for bupivacaine measurements. Polyimide membranes were synthesized from 4,4′-diaminobenzanilide (DABA) and different aromatic dianhydrides (pyromellitic dianhydride (PMDA), benzophenone-3,3′,4,4′-tetracarboxylic dianhydride (BPDA), 4,4′-oxydiphthalic anhydride (ODPA)) through two-step polycondenzation reactions. The structural properties of the obtained benzanilide based PIs were characterized by various analytical techniques. For the preparation of voltammetric electrodes, these polyimide films were coated with polyimide solution by drop-casting on the surface of a platinum working electrode. Due to the excellent film properties and suitable porosity, the prepared benzanilide based polyimide films were used as the membrane for selective determination of bupivacaine in the presence of interferents that included lactose, glucose and sucrose. For this reason, the selectivity of the modified electrode to bupivacaine obtained from the prepared PI film toward the potential interferences was investigated by differential pulse voltammetry (DPV). The results of voltammetric study showed that polyimide films responded to only bupivacaine at a potential of approximately +0.92 V. The polyimide membrane modified electrode showed a rapid response time, a high R-value of 0.9941, high reproducibility and good selectivity for bupivacaine. The limit of detection (LOD) and the limit of quantitation (LOQ) were determined to be 16.82 µM and 50.46 µM, respectively. Thus, benzanilide based polyimides may be successfully used as selective membranes for preparation of bupivacaine sensors. This structure may be a precursor for the preparation of simultaneous or needle-shaped sensors in the future.