Influence of Curing Accelerators on the Imidization of Polyamic Acids and Properties of Polyimide Films

In order to lower the imidization temperature of polyamic acids（PAA）, the catalytic activities of the curing agents p-hydroxybenzoic acid（PHA）, quinoline（QL）, benzimidazole（BI）, benzotriazole（BTA）, triethylamine（Et_3N） and 1, 8-diazabicyclo [5.4.0]undec-7-ene（DBU） were investigated in the process of thermal imidization of PAA. In addition, the effect of these various curing agents on the thermal stabilities and mechanical properties of the resultant polyimide（PI） films was determined. Quinoline was found to be an effective curing accelerator in the use of two-step method for synthesizing PI. Due to its moderate base strength, low steric crowding effect and moderate boiling point, quinoline could not only accelerate PAA to achieve imidization completely at 180 ℃, but also maintain the mechanical properties and thermal stability of the ordinary PI film. Any residual quinoline could be removed from PI films by heating at 250 ℃ for 4 h.

Effect of Low-temperature Imidization on Properties and Aggregation Structures of Polyimide Films with Different Rigidity

The traditional high-temperature preparation process of polyimide can cause many problems and limits the wider application in extreme conditions.An important challenge to be solved urgently is the reduction of imidization temperature.In this work,twelve kinds of polyimide films with different chain rigidity were prepared at low temperature of 200℃,in the absence or presence of imidazole used as the catalyst.The molecular rigidity and free volume were theoretically calculated,and relationship between structure and properties were systematically studied.The results show that imidization reaction under low temperatures is significantly affected by the rigidity of molecula r chains.The rigid structure of polyimide is not conducive to the low-temperature imidization,but this adverse effect can be eliminated by adding catalyst,resulting the notably increased imidization degree.The optical and thermal properties can be improved to a certain extent for the chemically catalyzed system,resulting in relatively higher heat resistance and thermal stability.While the mechanical performance could be determined by com plicating factors,greatly different from polyimide films prepa red by high temperature method.To investigate aggregation structures of film s,the effect of chain rigidity and catalyst on the stacking or orientation of molecular chains was further elaborated.This wo rk can contribute to the understanding of chemically catalyzed imidization that is rarely reported in the existing research,and will provide guidance for the low-temperature preparation of high-performance polyimides.

Comparison of Different Methods for Determining the Imidization Degree of Polyimide Fibers

In this study, polyimide fibers at different stages of imidization were characterized by TGA, DSC, and FTIR. The imidization degree （ID） calculated by TGA was based on the weight loss of each sample, which was caused by the imidization of residual amic acid groups. The results of TGA showed good regularity with the thermal treatment temperature of the PI fibers. For DSC, the ID was calculated based on the area of endothermal peak of each sample. Compared with TGA, DSC showed a relatively higher value because the endothermal peak was reduced by the exothermic re-formation of polyamic acid which may be partially degraded during thermal treatment. The IDs obtained by the FTIR spectra generally showed poorer regularities than those obtained by both TGA and DSC, especially for the results calculated using the 730 cm^-1 band. Based on the 1350 cm^-1 band, the obtained IDs showed better agreement with the TGA or DSC results. The results obtained by these three methods were compared and analyzed. The ID obtained by TGA showed much more reliability among these three methods.

Isomeric fluorescence sensors for wide range detection of ionizing radiations

In order to achieve a wider range of ionizing radiations detection,novel fluorescence sensing materials have been developed that utilize the fluorescence enhancement phenomenon caused by the intramolecular photoinduced electron transfer(PET)effect.Two perylene diimide isomers PDI-P and PDI-B were designed and synthesized,and their molecular structures were characterized by high-resolution Fourier transform mass spectrometry(HRMS),nuclear magnetic resonance hydrogen and carbon spectroscopy(~1H and~(13)C NMR).The interaction between ionizing radiation and fluorescent molecules was simulated by HCl titration.The results show that combining PDIs and HCl can improve fluorescence through the retro-PET process.Despite the similarities in chemical structures,the fluorescent enhancement multiple of PDI-B with aromatic amine as electron donor is much higher than that of PDI-P with alkyl amine.In the direct irradiation experiments of ionizing radiation,the emission enhancement multiples of PDI-P and PDI-B are 2.01 and 45.4,respectively.Furthermore,density functional theory(DFT)and time-dependent density functional theory(TDDFT)calculations indicate that the HOMO and HOMO-1 energy ranges of PDI-P and PDI-B are 0.54 e V and 1.13 e V,respectively.A wider energy range has a stronger driving force on electrons,which is conducive to fluorescence quenching.Both femtosecond transient absorption spectroscopy(fs-TAS)and transient fluorescence spectroscopy(TFS)tests show that PDI-B has shorter charge separation lifetime and higher electron transfer rate constant.Although both isomers can significantly reduce LOD during PET process,PDI-B with aromatic amine has a wider detection range of 0.118—240 Gy due to its larger emission enhancement,which is a leap of three orders of magnitude.It breaks through the detection range of gamma radiation reported in existing studies,and provides theoretical support for the further study of sensitive and effective new materials for ionizing radiation detection.

Assessment of Fibrinolytic Activity in Gastric Cancer

Objectives: To explore the relationship between thrombin-antithrombin complex (TAT), plasmin—α plasmin inhibitor complex (PIC), thrombomodulin (TM), tissue plasminogen activator/plasminogen activator inhibitor-1 complex (t-PAIC) and Gastric cancer. Methods: The plasma levels of TAT, TM, t-PAIC and PIC in patients with gastric cancer (40 in the initial diagnosis group and 35 in the post-treatment group) and 40 healthy controls were measured by chemiluminescent enzyme immunoassay. Then analyze the differences between these indicators in different stages of gastric cancer patients and healthy controls. Results: 1) The plasma levels of TAT, TM, t-PAIC and PIC in the newly diagnosed gastric cancer group were higher than those in the control group and the post-treatment group (P 0.05). 2) The plasma levels of TAT, TM, t-PAIC and PIC were not significantly different among the effective treatment group, the ineffective treatment group and the healthy control group. Conclusion: The changes of TAT, TM, t-PAIC and PIC levels are closely related to the development of patients with gastric cancer, and their increase may indicate that patients have a high risk of thrombosis.

Electrochemical Properties of PP13TFSI-LiTFSI-P（VdF-HFP） Ionic Liquid Gel Polymer Electrolytes

N-Methyl-N-propylpiperidiniumbis（trifluoromethanesulfonyl）imide （PP13TFSI）, bis（triflu- oromethanesulfonyl）imide lithium salt （LiTFSI）, and poly（vinylidene difluoride-co- hexafluoropropylene） （P（VdF-HFP）） were mixed and made into ionic liquid gel polymer electrolytes （ILGPEs） by solution casting. The morphology of ILGPEs was observed by scanning electron microscopy. It was found that the ILGPE had a loosened structure with liquid phase uniformly distributed. The ionic conductivity, lithium ion transference num- bet and electrochemical window were measured by electrochemical impedance spectroscopy, chronoamperometric and linear sweep voltammetry. The ionic conductivity and lithium ion transference number of this ILGPE reached 0.79 mS/cm and 0.71 at room temperature, and the electrochemical window was 0 to 5.1 V vs. Li＋/Li. Battery tests indicated that the ILGPE is stable when being operated in Li/LiFePO4 batteries. The discharge capacity maintained at about 135, 117, and 100 mAh/g at 30, 75, and 150 mA/g rates, respectively. The capacity retentions were almost 100% after 100 cycles without little capacity fading.

Effect of BaNH,CaNH,Mg3N2 on the activity of Co in NH3 decomposition catalysis

Development of active and non-noble metal-based catalyst for H2 production via NH3 decomposition is crucial for the implementation of NH3 as a H2 carrier.Co-based catalysts have received increasing attention because of its high intrinsic activity and moderate cost.In this work,we examined the effect of BaNH,CaNH and Mg3 N2 on the catalytic activity of Co in the NH3 decomposition reaction.The H2 formation rate ranks the order as Co-BaNH>Co-CaNH>Co-Mg3 N2≈Co/CNTs within a reaction temperature range of 300-550℃.It is worth pointing out that the H2 formation rate of Co-BaNH at 500℃reaches20 mmolH2 gcat-1 min-1,which is comparable to those of the active Ru/Al2 O3(ca.17 mmolH2 gcat-1 min1)and Ru/AC(21 mmolH2 gcat-1 min-1)catalysts under the similar reaction conditions.In-depth research shows that Co-BaNH exhibits an obviously higher intrinsic activity and much lower Ea(46.2 kJ mol-1)than other Co-based catalysts,suggesting that BaNH may play a different role from CaNH,Mg3 N2 and CNTs during the catalytic process.Combined results of XRD,Ar-TPD and XAS show that a[Co-N-Ba]-like intermediate species is likely formed at the interface of Co metal and BaNH,which may lead to a more energy-efficient reaction pathway than that of neat Co metal for NH3 decomposition.

Synthesis and characterization of mixing soft-segmented waterborne polyurethane polymer electrolyte with room temperature ionic liquid

Composite polymer electrolytes based on mixing soft-segment waterborne polyurethane （WPU） and 1-butyl-3-methylimidazolium bis[（trifluoromethyl）sulfonyl]imide （BMImTFSI） have been prepared and characterized. The addition of BMImTFSI results in an increase of the ionic conductivity. At high BMImTFSI concentration （BMImTFSI/WPU = 3 in weight ratio）, the ionic conductivity reaches 4.27 × 10^-3 S/cm at 30 ℃. These composite polymer electrolytes exhibit good thermal and electrochemical stability, which are high enough to be applied in lithium batteries.

Synthesis of Methyl-substituted Phthalazinone-based Aromatic Poly(amide imide)s

A series of novel aromatic poly ( amide imide)s containing phthalazinone moieties were prepared from 2-(4-aminophenyl)-4-[3-methyl-4-(4-aminophenoxy)-2,3-phthalazinone-1], a novel diamine 1 with four diimide-dicarboxylic acids by Yamazaki phosphorylation method with the inherent viscosity of 0.36~0.65 dL/g. These polymers had high glass transition temperatures above 300C and they lost 10% weight between 426~475C in N2. The structure of diamine 1 and the polymers was confirmed by IR, 1H NMR and MS. The obtained polymers were readily soluble in polar solvents such as NMP, m-cresol etc. and easily cast into tough, flexible films. The X-ray indicated that they are all amorphous.

Synthesis and Characterization of Poly(ether imide)s Containing m-Methyl and Phthalazinone Moieties

Three novel poly(ether imide)s were synthesized by one-step solution polymerization from 2-(3, 4-dicarboxyl-N-phenyl)-4-(3, 4-dicarboxyl-phenoxyl-4-(2-methyl)-phenyl)-2, 3- phthal-azin-1-one dianhydride and three amines, and characterized. The polymers show good solubility and thermal properties.

Electrochemically-driven interphase conditioning of magnesium electrode for magnesium sulfur batteries

The earth-abundant magnesium metal is a kind of promising anode material due to its low reduction potential (-2.356V vs. SHE), high volumetric and gravimetric specific capacities of 3882 mAh cm-3 and 2234 mAh g_1 respectively [1]. Moreover, the magnesium anode shows high safety due to the non-dentritic electrodeposition mechanism during cycling, which is related to the strong Mg-Mg bonding and the consequent high energy barrier between the crystal boundaries of different crystal orientation [2].

SYNTHESIS OF NEW AROMATIC POLY(AMIDE IMIDE)S FROM UNSYMMETRICAL EXTENDED DIAMINE CONTAINING A PHTHALAZINONE MOIETY

The direct polymerization of an unsymmetrical kink non-coplanar heterocyclic diamine (1) with various aromatic bis(trimellitimide)s (2a-e) using triphenyl phosphite and pyridine as condensing agents could generate a series of new aromatic poly(amide imide)s (3a-e) containing the kink non-coplanar phthalazinone heterocyclic units in the polymer main chains with inherent viscosities of 0.58-0.66 dL/g. The polymers are readily soluble in a variety of solvents such as N,N- dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, N-methyl-2-pyrrolidinone, pyridine and m-cresol and can be cast to form flexible and tough films. The glass transition temperatures of polymers (Tg) are in the range of 301-327°C, and the temperatures for 5% weight loss in nitrogen are in the range of 498-521 'C.

Synthesis and Characterization of Poly (ether imide)s Containing Phthalazinone and Isopropyl Moieties

A novel poly(ether imide)s containing phthalazinone and isopropyl moieties derived from 2-(4-aminophenyl)-4-[4-(4-aminophenoxy)phenyl]-phthalazin-1-one and bisphenol-A diphthalic anhydride was synthesized by one-step solution condensation polymerization in nr-cresol. The polymer was characterized by FTIR, NMR, molecular weights, glass transition temperature, thermal degradation temperature and WAXD.

Acidic Polyester Imides as Thermally Stable Binder Polymers for Negative-Tone Black Photoresist

Polyimides are well-known for their high chemical inertness and thermal stability. However, it is usually challenging to synthesize UV-curable polyimides since the imidization reaction requires such harsh conditions that acrylate type double bonds cannot withstand. In this work, synthetic methods are developed to obtain polyester-imide type binder polymers with high thermal stability, high compatibility with the other components of the black photoresist, and fine photolithographic patterning property for the negative-tone black photoresist. The syntheses of diimide-diacid or diimide-diol intermediates for the polyesterification with dianhydride gave polyester imides which meets this requirement. The photolithographic tests have shown that the patterning of the micron-sized PDL of the organic light emitting diode (OLED) panel could be obtained. This work will interest the researchers working on the design and optimization of thermally stable binder polymers.

Reactions of Imidates with Phenoxyacetyl Chloride

The reactions of imidates including cyclic imidates, oxazolines and dihydrooxazine with phenoxyacetyl chloride, were investigated. The results indicate that diacylamide or acylamide was generated from N-phenoxyacetylated imidates, while cyclic imidate oxazolines underwent a ring-opening reaction to yield different amides depending on the reaction conditions. Even under non-nucleophilic conditions, no β-lactam-fused oxazoline derivative was obtained.

Instability of lithium bis(fluorosulfonyl)imide(LiFSI)–potassium bis(fluorosulfonyl)imide(KFSI) system with LiCoO_2 at high voltage

The cycling performance, impedance variation, and cathode surface evolution of the Li/LiCoO2 cell using Li FSI–KFSI molten salt electrolyte are reported. It is found that this battery shows poor cycling performance, with capacity retention of only about 67% after 20 cycles. It is essential to understand the origin of the instability. It is noticed that the polarization voltage and the impedance of the cell both increase slowly upon cycling. The structure and the properties of the pristine and the cycled LiCoO2 cathodes are investigated by x-ray diffraction（XRD）, scanning electron microscopy（SEM）, Raman spectroscopy, x-ray photoelectron spectroscopy（XPS）, and transmission electron microscopy（TEM）. It is found that the LiCoO2 particles are corroded by this molten salt electrolyte, and the decomposition by-product covers the surface of the LiCoO2 cathode after 20 cycles. Therefore, the surface side reaction explains the instability of the molten salt electrolyte with LiCoO2.

Carbide derived carbon electrode with natural graphite addition in magnesium electrolyte based cell for supercapacitor enhancements

Herein,we have presented a supercapacitor based on carbide derived carbon（CDC） electrode with natural graphite（NG） addition.The capacitor was analyzed at 22°C by cyclic voltammetry,galvanostatic charge-discharge and impedance techniques using a 0.5 mol/L of magnesium（II）bis（trifluoro methanesulfonyl） imide（Mg TFSI） in ethylene carbonate-propylene carbonate（EC ：PC = 1 ：1,v/v） as electrolyte.The results conclude that the CDC cell enhancements have been proven by the composite electrode（5%–30% NG to CDC） especially on the cell efficiency and voltage i.e.,the CDC cell around 2.5 V limit was improved.An obtainable specific capacitance,real power and energy density are 15 F g-1,1.2 k W kg-1and 15 Wh kg-1,respectively.

Implementation of a choline bis(trifluoromethylsulfonyl)imide aqueous electrolyte for low temperature EDLCs enabled by a cosolvent

We report a carbon/carbon capacitor based on micro/mesoporous carbon electrodes with cost-effective and eco-friendly aqueous choline bis(trifluoromethylsulfonyl)imide(Ch TFSI)electrolyte with a cosolvent enabling low-temperature operation down to-30℃.For this purpose,a Mg O-templated hierarchical carbon(MP98B)with an average mesopore diameter of 3.5 nm was prepared by pyrolysis of magnesium citrate hydrate at 900℃.To reach lower temperatures,the melting point and viscosity of the aqueous electrolyte were reduced by mixing water(W)with an organic solvent(methanol,M,or isopropanol,I)of high dielectric constant and low viscosity.5 mol kg^(-1)(5 m)Ch TFSI in an optimized volume fraction of cosolvent,M_(0.75)W_(0.25),and I_(0.75)W_(0.25),showed the highest conductivity;the higher conductivity in M_(0.75)W_(0.25)(22.8 and 3.1 m S cm^(-1) at 20 and-30℃,respectively)than in I_(0.75)W_(0.25)(8.5 and0.5 m S cm^(-1)at 20 and-30℃,respectively)is attributed to the lower viscosity of the M_(0.75)W_(0.25)solution.The electrochemical stability window(ESW)of 5 m Ch TFSI in M_(0.75)W_(0.25)and I_(0.75)W_(0.25)(1.6 V)on an MP98B electrode was determined by applying the S-method.Meanwhile,by adjusting the mass ratio of the two electrodes,a MP98B/MP98B capacitor using the 5 m electrolyte in M_(0.75)W_(0.25)could operate with a good life span up to 1.6 V while exhibiting a better charge propagation,greater specific capacitance,and higher specific energy than in I_(0.75)W_(0.25).

Rhodium(Ⅲ)-catalyzed chelation-assisted C-H imidation of arenes via umpolung of the imidating reagent

Rh(Ⅲ)-catalyzed, chelation-assisted oxidative C-H imidation of arenes with N-H imide have been realized using PhI(OAc)2 as an oxidant. This transformation exhibits a broad substrate scope and tolerates various functional groups. The reaction proceeded via in situ generation of an iodine(Ⅲ) imido. DFT calculations suggest that this oxidative imidaton system proceeds via a Rh(Ⅲ)-Rh(Ⅴ)-Rh(Ⅲ) pathway.

Synthesis and Crystal Structure of N-Phenylbis(ferrocenecarboxyl)imide

The ferrocenyl compound, N-phenylbis（ferrocenecarboxyl）imide （C28H23NO2Fe2, Mr = 517.17）, was synthesized and structurally characterized by means of X-ray single-crystal diffraction. It crystallizes in monoclinic, space group C2/c with a = 21.374（14）, b = 10.430（7）, c = 10.741（7） A, β= 114.184（8）°, V= 2184（2） A^3, Z= 4, Dc = 1.573 g/cm^3, F（000） = 1064, μ（MoKα） = 1.355 mm ^-1, T= 291（2） K, the final R = 0.0548 and wR = 0.1437 for 1524 observed reflections with 1 〉 2σ（I）. In this compound, the nitrogen atom links two ferrocenyl groups and one phenyl group forming a novel imido derivative.