Microspherical structures find broad application in chemistry and materials science, including in separations and purifications, energy storage and conversion, organic and biocatalysis, and as artificial and bioactive scaffolds. Despite this utility, the systematic diversification of their morphology and function remains hindered by the limited range of their molecular building blocks. Drawing upon the design principles of reticular synthesis, where diverse organic molecules generate varied porous frameworks, we show herein how analogous microspherical structures can be generated under mild conditions. The assembly of simple organic molecules into microspherical structures with advanced morphologies represents a grand challenge. Beginning with a partially condensed Schiff base which self-assembles into a hierarchical organic microsphere, we systematically synthesized sixteen microspheres from diverse molecular building blocks. We subsequently explicate the mechanism of hierarchical assembly through which these hierarchical organic microspheres are produced, isolating the initial monomer, intermediate substructures, and eventual microspheres. Furthermore, the open cavities present on the surfaces of these constructs provided distinctive adsorptive properties, which we harnessed for the immobilization of enzymes and bacteriophages. Holistically, these hierarchical organic microspheres provide an approach for designing multi-functional superstructures with advanced morphologies derived from simple organic molecules, revealing an extended length scale for reticular synthesis.

Low Gain Avalanche Detectors (LGAD) for the High-Granularity Timing Detector (HGTD) are crucial in reducing pileups in the High-Luminosity Large Hadron Collider. Numerous studies have been conducted on the bulk irradiation damage of LGADs. However, few studies have been carried out on the surface irradiation damage of LGAD sensors with shallow carbon implantation. In this paper, the IHEP-IME LGADs with shallow carbon implantation were irradiated up to 2 MGy using gamma irradiation to investigate surface damage. Important characteristic parameters, including leakage currents, breakdown voltage (BV), inter-pad resistances, and capacitances, were tested before and after irradiation. The results showed that the leakage current and BV increased after irradiation, whereas overall inter-pad resistance exhibited minimal change and remained above 10 9 Ω before and after irradiation. Capacitance was found to be less than 4.5 pF with a slight decrease in the gain layer depletion voltage (V gl ) after irradiation. No parameter affected by the inter-pad separation was observed before and after irradiation. All characteristic parameters meet the requirements of HGTD, and this design can be used to further optimization.

Several polyimides were prepared via two-step polycondensation from novel 2,5-furandicarboxylic acid–based diamine, 2,5-bis[4-(4-aminophenoxy)benzoyl]furan, with commercial dianhydrides. The chemical structures of the monomers and polymers were characterized by FT-IR and NMR in detail, respectively. The polyimides exhibited high performances with 5 wt% weight loss temperatures of over 410 o C, glass transition temperatures of over 214 o C, and tensile strengths and Young’s moduli of up to 130 MPa and 3.2 GPa, respectively. The thermal crosslinking mechanism was studied by FT-IR, Raman spectroscopy, and model reaction analysis, which showed the Diels–Alder reaction between the furan group and diphenylethylene group was the main reaction. The crosslinked polyimide films showed improved solvent resistance, and thermal and mechanical properties.

基于单体4-苯基醚-1,3-二胺制备了一种新型乙炔基封端热固性聚酰亚胺.利用傅里叶变换红外光谱仪、核磁共振氢谱仪和X射线衍射仪对其结构进行表征,其结果表明制备得到了相应结构的预聚体.利用差示扫描量热仪测得预聚体的玻璃化转变温度(Tg)仅为155℃.预聚体在有机溶剂中具有高的溶解性,常温下在N-甲基吡咯烷酮中的溶解度高于50％.熔体黏度测试表明,预聚体的最低熔体黏度在237℃时为47.5 Pa·s.动态力学热分析仪测试表明,交联固化后树脂的Tg值高达335℃,具有非常高的耐温性.热失重曲线表明,该种热固性聚酰亚胺树脂具有高的热分解稳定性,在空气中5％热失重温度为535℃,氮气中800℃的残炭率为57％.

A reactive diluent (ODA-PEPA) and a flexible phenylethynyl-terminated imide oligomer (PEI-PEPA) were designed and synthesized based on the 2,3,3’,4’-diphenyl ether tetracarboxylic acid dianhydride (a-ODPA), 3,4’-oxydianiline (3,4’-ODA), and 4-phenylethynylphthalic anhydride (PEPA). Solution blended systems with the addition of 5, 10, and 15 wt% ODA-PEPA to PEI-PEPA oligomer and their cured resin systems were prepared. Results showed that ODA-PEPA is semi-crystalline in nature. The Tg values of cured resins were improved from 273 °C to 280 °C by the addition of ODA-PEPA, due to the higher crosslink densities. In addition, rheological properties of blends showed lower melt viscosity and wider processing window, revealing improved melt processabilities for potential application in making advanced composites. The isothermal viscosity in 280 °C of PEI-PEPA containing 15 wt% ODA-PEPA reactive diluent decreased by two thirds, due to the low molecular weight of ODA-PEPA. The cured blends demonstrated high thermal stability and heat resistance. 5 wt% thermal decomposition temperatures (Td5) of the cured blends were above 549 °C and 547 °C in N2 and air atmosphere, respectively. The char yield reported at 800 °C in N2 atmosphere increased from 58.8% to 63.7 % with the addition of ODAPEPA. Meanwhile, the cured polyimides blends possessed good bond strength (> 9.3 MPa).

为了解决高填充树脂挤出过程中出现的耗能高、分散不良等问题,本文以正戊烷作为增塑剂,模拟工业生产的双阶挤出工艺.按照国家标准测量挤出颗粒料的性能.实验结果表明:正戊烷作为增塑剂可降低挤出机电机的能耗约37％,使一次挤出的颗粒料拉伸强度提高23％,熔融指数提高130％;正戊烷的损耗可控制在树脂质量分数的1.5％以下,适用于通用树脂的挤出.

Novel asymmetric bismaleimide (BMI) oligomers with different molecular weights and dianhydrides were designed and synthesized by 3,4′‐oxydianiline (3,4′‐ODA), 2,3,3′,4′‐oxydiphthalic dianhydride (a‐ODPA), and 2,3,3′,4′‐biphenyltetracarboxylic dianhydride (a‐BPDA). The chemical structures of BMI oligomers were confirmed by Fourier transform infrared spectrometry (FTIR) and gel permeation chromatography (GPC). X‐ray diffraction (XRD) exhibited broad peaks, suggesting amorphous structures. Heat flow curves of oligomers measured by differential scanning calorimeter (DSC) displayed wide processing window due to low glass transition temperatures (Tg). BMI oligomers exhibited high solubility in common organic solvents. Particularly, the OD‐BMI‐1 oligomer exhibited excellent solubility of more than 50 wt% in DMAc solvent. Tg value and minimum complex viscosity of OD‐BMI‐1 oligomer were only 121 °C and 8.1 Pa · s, respectively. The cured BMI resins possess high thermal and thermal‐oxidative stability. The Tg and the temperature of 5% weight loss in nitrogen were above 256 and 449 °C, respectively, and the residual weight percentages at 800 °C were all >49%. Moreover, films made of BMI resins exhibited excellent mechanical properties flexibility, as confirmed by photograph and DMA results of films. The elongation at break of the prepared films was found to be high (almost >9.6%). POLYM. ENG. SCI., 59:2265–2272, 2019. © 2019 Society of Plastics Engineers

Two series of cardo polyimides were prepared from 1,4-bis(4-fluorophthalimide)cyclohexane with different trans/cis ratios and phenolphthalein/o-cresolphthalein via aromatic nucleophilic substitution reaction. The inherent viscosities of the synthesized polymers were found to be 0.55-0.66 dL g(-1) in N,N-dimethylacetamide. The cardo polyimides showed excellent solubility in organic solvents, high glass transition temperatures (T-g) of 275-312 degrees C and moderate thermal stability with 5% weight loss temperatures (T-d5%) of 415-441 degrees C in nitrogen and 370-436 degrees C in air. The polyimide films exhibited high optical transparency with cut-off wavelengths of 350-355 nm and moderate mechanical properties. The different properties of the polymers caused by trans and cis configurations of 1,4-diaminocyclohexane were also investigated. It was found that with an increasing content of trans configuration of 1,4-diaminocyclohexane in the polyimide backbone, T-g of the polyimides increased as well as T-d5%, while the solubility gradually decreased. The polyimide films had good optical transparency regardless of trans/cis configuration. (c) 2018 Society of Chemical Industry

The multi walled carbon nanotubes (MWNTs) have always been as the catalyst supporting materials, but for high-performance composite catalysts, the dispersion and functionalization of MWNTs are important challenging problems. In this paper, Electrocatalytically active palladium nanoparticles (Pd NPs) on MWNTs with the high-performance and excellent solubility polymer, poly(dimethylbenzimidazolium) iodide (P(DMBI)-I − ) as modifier and glue was first discussed. The results of transmission electron microscopy (TEM) demonstrate a better dispersion of MWNTs with the assist of P(DMBI)-I − . The Raman spectra indicate a strong π-π interaction between MWNTs and P(DMBI)-I − . Taking advantages of the coordination effect of imidazole groups and the electrostatic attraction to Pd NPs, the prepared Pd/MWNTs-P(DMBI)-I − (Pd/MPDI − ) hybrid is of well electrocatalytic activity to the ethanol fuel cells by electrochemical measurements. So it is believed that P(DMBI)-I − can be further applied in the dispersion of different carbon-based materials and metal nanoparticles for fabricating more novel composites for catalyst and electrode material.

A series of polyimides were prepared from the cardo bisphenol monomers which derived from phenolphthalein or o-cresolphthalein and the bis(fluorophthalimide)s which derived from trans-1,4-cyclohexanediamine by aromatic nucleophilic substitution,and the solubility,heat resistance and optical properties of these polymers were compared by changing the size of the pendant group of the diphenol. The results show that the glass-transition temperatures of polyimides are between 270 –316℃,and the series polyimides exhibit excellent thermal stabilities with the 5% weight loss temperatures of 401–434℃and the 10% weight loss temperatures of 419–446℃ in nitrogen. The polyimides have excellent solubility in conventional organic solvent. The polymer films have good transparency with UV cutoff wavelengths of lower than 354 nm,and the transmittances are mostly over 80% at 450 nm.

Novel highly soluble phenylethynyl-endcapped oligoimides with different calculated molecular weights were prepared by using mellophanic dianhydride and bis(4-amino-2-trifluoromethylphenyl)ether in the presence of 4-phenylethynyl phthalic anhydride as the reactive endcapping agent. The effect of molecular weights of the aromatic oligoimides on their solubility and processability as well as the thermal and mechanical properties of the thermal-cured polyimides was fully investigated. This kind of phenylethynyl-terminated imides exhibited excellent comprehensive properties. Most importantly, a big progress has been made in the solubility of the oligoimides in this paper. Most of the oligoimides showed excellent solubility (more than 33wt%) even in acetone, which was reported for the first time. And oligoimides with appropriate molecular weights also showed very good processability with minimum melt viscosities no higher than 120Pas by the rheological study. After thermally curing at 370 degrees C for 1hour, the cured flexible films showed very high glass transition temperatures up to 392 degrees C by dynamic mechanical analysis, and the temperature of 5% weight loss was higher than 500 degrees C in both air and N-2 atmosphere by thermogravimetric analysis. The cured films also exhibited very good toughness with elongation up to 9%.

Novel highly soluble phenylethynyl-endcapped oligoimides derived from mixed thioetherdiphthalic anhydride isomers (m-TDPA) and 5(6)-amino-1-(4-aminophenyl)-1,3,3-trimethylindane (DAPI), 4,4′-oxydianiline (4,4’-ODA) with 4-phenylethynylphthalic anhydride (PEPA) as a reactive endcapping agent were synthesized. The calculated molecular weights of all the oligoimides were 2500 g·mol−1.The effect of the mole ratio of DAPI/4,4’-ODA on solubility and melt viscosity of oligoimides as well as the thermal and mechanical properties of cured polyimide films was investigated. Experimental results indicated that DAPI greatly improved the solubility (>30 wt.%) of the oligoimides in low boiling points solvents when the content of DAPI was more than 10 mol% per total diamine. All the oligoimides exhibited very good processability with minimum melt viscosity lower than 60 Pa·s at about 330 °C. Tough and brown films were obtained after thermally cured at 370 °C for 1 h and dynamic mechanical analysis (DMA) showed that glass transition temperatures of the cured films increased up to 340 °C with the increasing content of DAPI. However, the thermal stability and mechanical properties decreased with the increase of DAPI content. The temperature of 5% weight loss was higher than 470 °C in both air and N2 atmosphere obtained by thermogravimetric analysis (TGA). And the tensile strengths of the cured films were about 60 MPa.

Two novel bio-based diamines are synthesized through introduction of renewable 2,5-furandicarboxylic acid (2,5-FDCA), and the corresponding aromatic polyimides (PIs) are then prepared by these diamines with commercially available aromatic dianhydrides via two-step polycondensation. The partially bio-based PIs possess high glass transition temperatures (T(g)s) in the range from 266 to 364 degrees C, high thermal stability of 5% weight loss temperatures (T(5%)s) over 420 degrees C in nitrogen and outstanding mechanical properties with tensile strengths of 79-138 MPa, tensile moduli of 2.5-5.4 GPa, and elongations at break of 3.0-12.3%. Some colorless PI films (PI-1-b and PI-1-c) with the transmittances at 450 nm over 85% are prepared. The overall properties of 2,5-FDCA-based PIs are comparable with petroleum-based PI derived from isophthalic acid, displaying the potential for development of innovative bio-based materials. (c) 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 1058-1066

Two series of polyimides (PIs) derived from bis(ether anhydride)s and bis(ester anhydride)s using 2,2′-bis(trifluoromethyl)biphenyl-4,4′-diamine were synthesized via solution polycondensation. The poly(ether imide)s could be formed by the conventional one-step method, while the poly(ester imide)s were only afforded by the two-step procedure. The resulting PIs had glass transition temperatures ( Tgs) in the range of 224–320°C and exhibited good mechanical properties with tensile strength in the range of 80.5–96.5 MPa, tensile moduli 2.7–6.9 GPa, and elongations at break 1.5–17.3%. It was found that the PIs derived from bis(ether anhydride)s showed higher thermal stability, better solubility, and transparency but lower Tg and higher water absorption compared with bis(ester anhydride)-based PIs due to the different ether and ester linkages.

It is a great challenge to develop semicrystalline polyimides exhibited significant recrystallization ability and fast crystallization kinetics from the melt. A series of semicrystalline polyimides based on 1,4-bis(3,4-dicarboxyphenoxy)benzene dianhydride (HQDPA) and different diamines, including 1,3-bis(4-aminophenoxy)benzene (TPER), 1,4-bis(4-aminophenoxy)benzene (TPEQ), 4,4′-oxydianiline (4,4′-ODA) and 4,4′-bis(4-aminophenoxy)biphenyl (BAPB), end capped with phthalic anhydride were synthesized. Crystallization and melting behaviors were investigated by differential scanning calorimetry (DSC). The polyimide derived from HQDPA/TPER (PI-1) exhibited a glass transition temperature (Tg) at 190 °C and double melting temperatures (Tms) at 331 °C and 350 °C, and the polyimide derived from HQDPA/TPEQ (PI-2) displayed a Tg at 214 °C and a Tm at 388 °C. PI-1 and PI-2 showed significant recrystallization ability from melt and high crystallization rate by isothermal crystallization kinetics study, while polyimides based on 4,4′-ODA and BAPB lost crystallizability once taken to the melt. These polyimides also exhibited excellent thermo-oxidative stability with 5% weight loss temperature higher than 500 °C and good mechanical properties with tensile moduli of 2.0–3.3 GPa, tensile strengths of 85–105 MPa and elongations at break of 5–18%. PI-1 also possessed outstanding melt flowability with less than 300 Pa·s around 370 °C by rheological measurements.

A series of polyimides (PIs) derived from 1,4-cyclohexylene bis(trimellitate anhydride) (TACH) was synthesized by conventional two-step method with chemical imidization. The resulting PIs had glass transition temperatures ( Tgs) in the range of 188–240°C and exhibited good mechanical properties with tensile strengths of 50.0–90.2 MPa, tensile moduli of 2.2–3.9 GPa, and elongations at break of 2.9–5.8%. These PI films showed high optical transparency with cut-off wavelengths of 345–369 nm and high transmittance at 500 nm with more than 84%. Compared with PIs derived from 1,4-bis(3,4-dicarboxyphenoxy)cyclohexane dianhydride, the TACH-based PIs showed higher Tg, better solubility, and competitive transparency.

Novel imide oligomers (calculated molecular weights: 1250-5000 g mol(-1)) based on the mixture of thioetherdiphthalic anhydride isomers (m-TDPA) with 2-phenyl-4,4-diaminodiphenyl ether (p-ODA) in the presence of 4-phenylethynylphthalic anhydride (PEPA) as reactive endcapping agent were prepared. Then pyromellitic dianhydride (PMDA) was introduced to the polymerization of m-TDPA/p-ODA (mole(m-TDPA):mole(PMDA) = 1:1). The effect of molecular weights and polymer chemical structures of the aromatic oligomers on their processability and solubility as well as the thermal and mechanical properties of the thermal-cured polyimides (PIs) was systematically investigated. All the oligomers showed good solubility (more than 30 wt%) in N-methyl-2-pyrrolidone and very low melt viscosities. The minimum melt viscosities of Oligo-5 was 61.5 Pa s at 321 degrees C. The melt viscosity of the oligomers increased with the increase of molecular weight. After thermally curing at 370 degrees C for 1 h, the thermoset PIs exhibited good thermal properties. The glass transition temperatures of oligomers measured by differential scanning calorimetry were in the range of 264-337 degrees C, and the temperature of 5% weight loss was higher than 505 degrees C. The cured films also demonstrated good mechanical properties with tensile strength and modulus greater than 52 MPa and 2.9 GPa, respectively.

A series of oligomers based on the mixture of thioetherdiphthalic anhydride isomers and 4,4′-oxydianiline with 4-phenylethynylphthalic anhydride as reactive endcapping reagent were prepared. The calculated molecular weights were in the range of 1150–5070 g mol−1 with different degrees of polymerization ( n = 1, 3, 5, 7, and 9). The effect of molecular weight of the aromatic oligomers on their processability and solubility as well as the thermal and mechanical properties of the thermal-cured polyimides (PIs) was systematically investigated. The typical oligomer (Oligo-1) could be melted at temperatures of 289–334°C to yield stable molten fluid with melt viscosity below 1.0 Pa s. The melt viscosity of the oligomers increased with the increasing molecular weight. After thermally curing at 370°C, the thermoset PIs exhibited good thermal properties. The glass transition temperatures of oligomers measured by differential scanning calorimetry were in the range of 286–326°C, and the temperature of 5% weight loss was higher than 524°C. The cured films also showed good mechanical properties with tensile strength above 72 MPa and modulus more than 2.5 GPa.

A series of polyimides (PI) were prepared from 3,3′,4,4′–hydroquinone diphthalic dianhydride(4,4′–HQDPA), 2, 2′,3,3′–hydroquinone diphthalic dianhydride (3,3′–HQDPA) with different ratios of the isomers and 4,4′–oxydianiline (4,4’–ODA) by the conventional two-step method. Solubility, thermal properties and melt processability of the copolyimides were investigated and compared with corresponding homopolyimides. The results show that all the polyimides exhibite excellent thermal stabilities with the 5% weight loss temperatures (Td5%) of 500~521℃ in air and 507~538℃ in nitrogen respectively. With the increasing of 3,3′–HQDPA,the polymers exhibite a regular increase in solubility and glass transition temperatures (Tg), andTg increase from 223 to 257℃. The melt processability is found to be dependent on the ratios of dianhydride units,Tg,solubility and melt flowability of copolyimides could be adjusted by the mole ratio of the isomers,so that the copolyimides could satisfy different applications. The copolyimides show better melt fluidity than the homopolyimides,and the copolyimide exhibite the best melt flowability when the mole ratio of 3,3′–HQDPA and 4,4′–HQDPA is 1∶1,which could be used as high performance melt–processable polyimides.

Transparent polyimides derived from ester-containing dianhydrides with different electron affinities were synthesis and the different properties caused by different ester linkages were well investigated.