Two-dimensional (2D) black phosphorus (BP) shows thickness dependent direct energy band-gaps in association with strong light-matter interaction and broadband optical response, rendering it with promising optoelectronic advantages particularly at the telecommunication band. However, intrinsic BP suffers from irreversible oxidization, restricting its competences toward real device applications. As one potential of 2D materials, all-optical signal processing sensitively depends on the strength of light−matter interaction. BP can be utilized as a novel optical medium. Herein, fewlayer BP is synthesized with metal-ion-modification against oxidation and degradation, and then the feasibility of BP-coated microfiber as an optical Kerr switcher and a four-wave-mixing-based wavelength converter is demonstrated. The wavelength-tuning, long-term stability, wide-band RF frequency, and time-repeating measurements confirm that this optical device can operate as a broadband all-optical processor. It is further anticipated that metal-ion-modified BP might provide a new effective option for photonic applications toward high performances and enhanced stability.

The synthesis of mellophanic dianhydride (MPDA), an isomer of pyromellitic dianhydride (PMDA), was studied. A trend of forming cyclic oligomers in the reactions of MPDA with 4,4‘-oxydianiline (ODA) or 4,4‘-methylenedianiline (MDA) in DMAC was found. The cyclic dimer from MPDA/MDA was isolated and fully characterized, including an X-ray crystallographic analysis. The reactions of MPDA with aromatic diamines were found much more complicated than those of PMDA. A model study was performed to clarify the reactions. Several byproducts were isolated and characterized, so that, in an usual two-step process to prepare polyimides, imide, amide linkage, and carboxylic group may be involved in the polymer structure. The water, either existing in solvent or being generated during the imidization, is the main reason for the side reactions. The properties of some polyimides derived from MPDA and diamines were tested and compared with those of the isomeric polyimides derived from PMDA.

Phosphorene, mono/few‐layered black phosphorous with advantages of tunable energy bandgaps and strong light–matter interaction, is fabricated by electrochemical intercalation with large area (≈3 µm) and controllable thickness (mainly four layers). Thanks to the direct gap and resonant absorption of four‐layer phosphorene at the telecommunication band, all‐optical thresholding and optical modulation are demonstrated for optical communications by using few‐layer phosphorene‐decorated microfibers. This device is experimentally verified as an efficient noise suppressor that can enhance the signal‐to‐noise ratio and reshape the deteriorated signal pulse, and also as an optical modulator that can switch the signal on/off by pumping light. The findings, as the first prototypic device of all‐optical thresholding and optical modulation, might facilitate the development of phosphorene‐based optical communication technologies.

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A new synthetic route to 2,2′,3,3′‐BTDA (where BTDA is benzophenonetetracarboxylic dianhydride), an isomer of 2,3′,3′,4′‐BTDA and 3,3′,4,4′‐BTDA, is described. Single‐crystal X‐ray diffraction analysis of 2,2′,3,3′‐BTDA has shown that this dianhydride has a bent and noncoplanar structure. The polymerizations of 2,2′,3,3′‐BTDA with 4,4′‐oxydianiline (ODA) and 4,4′‐bis(4‐aminophenoxy)benzene (TPEQ) have been investigated with a conventional two‐step process. A trend of cyclic oligomers forming in the reaction of 2,2′,3,3′‐BTDA and ODA has been found and characterized with IR, NMR, matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry, and elemental analyses. Films based on 2,2′,3,3′‐BTDA/TPEQ can only be obtained from corresponding polyimide (PI) solutions prepared by chemical imidization because those from their polyamic acids by thermal imidization are brittle. PIs from 2,2′,3,3′‐BTDA have lower inherent viscosities and worse thermal and mechanical properties than the corresponding 2,3′,3′,4′‐BTDA‐ and 3,3′,4,4′‐BTDA‐based PIs. PIs from 2,2′,3,3′‐BTDA and 2,3′,3′,4′‐BTDA are amorphous, whereas those from 3,3′,4,4′‐BTDA have some crystallinity, according to wide‐angle X‐ray diffraction. Furthermore, PIs from 2,2′,3,3′‐BTDA have better solubility, higher glass‐transition temperatures, and higher melt viscosity than those from 2,3′,3′,4′‐BTDA and 3,3′,4,4′‐BTDA. Model compounds have been prepared to explain the order of the glass‐transition temperatures found in the isomeric PI series. The isomer effects on the PI properties are discussed. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2130–2144, 2004

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A sol-gel process has been developed to prepare polyimide (PI)/Al 2 O 3 hybrid films with different contents of Al 2 O 3 based on pyromellitic dianhydride (PMDA) and 4,4 0 -oxydianiline (ODA) as monomers. FESEM and TEM images indicated that Al 2 O 3 particles are relatively well dispersed in the polyimide matrix after ultrasonic treatment of the sol from aluminum isopropoxide and thermal imidization of the gel film. The dimensional stability, thermal stability, mechanical properties of hybrid PI films were improved obviously by an addition of adequate Al 2 O 3 content, whereas, dielectric property and the elongation at break decreased with the increase of Al 2 O 3 content. Surprisingly, the corona-resistance property of hybrid film was improved greatly with increasing Al 2 O 3 content within certain range as compared with pure PI film. Especially, the hybrid film with 15 wt % of Al 2 O 3 content exhibited obviously enhanced corona-resistance property, which was explained by the formation of compact Al 2 O 3 network in hybrid film.