•Effects of various solvents on stability of polydichlorophosphazene were presented.•Structural behaviors of PDCP in various solvents were also demonstrated.•All structures were characterized by various analyses to predict their mechanisms.•Active P+ ions can lead to degradation, branching and cross-linking of PDCP.Polyphosphazenes are an important class of polymers due to their structural flexibility, synthetic versatility and their wide range of properties. Among them, poly(dichlorophosphazene) (PDCP) is an essential intermediate from which most of the polyphosphazenes can be synthesized through nucleophilic substitution reaction. One of the main challenges in its synthetic procedure is to control the side reactions such as undesirable processes of polymer degradation, branching and cross-linking owing to instability of PDCP. In this paper, we have investigated the stability of PDCP and its structural behaviors by the influence of various solvents such as DMSO, DMF, DMAc. THF, DCM, PX, and etc. The polarity of the solvents affected the P+ ions of PDCP, water absorption capacity and its intermolecular interactions which are responsible for degradation and cross-linking of PDCP. The polymeric species and their mechanistic chemistry are characterized by multinuclear NMR, FT-IR and mass spectrometry to confirm their detail structures by changing the solvents.

•Ferrocene based phosphazene microspheres have been successfully synthesized.•The diameters of the cross-linked microspheres vary from 0.3 to 1.3 μm.•The microspheres act as a potent adsorbent for the removal of methylene blue.•These multifunctional microspheres can possibly be used in several applications.Ferrocenylphosphazenes have been attracting increasing attention for their special properties and potential applications. We describe here a new high-throughput synthesis of cross-linked poly(cyclotriphosphazene-co-bis(aminomethyl)ferrocene) microspheres via the polycondensation of hexachlorocyclotriphosphazene and 1,1′-di(aminomethyl)ferrocene by precipitation polymerization. The mean diameter of the microsphere varies from 0.3 to 1.3 μm, depending on the concentrations of both monomers in a calculated molar ratio. The morphology and structure of microspheres were characterized by FT-IR, SEM, EDX and TEM analyses. TG analysis demonstrated their superior thermal stability owing to the presence of high cross-linked bonding. Magnetic measurements revealed that the microspheres are superparamagnetic with a saturation magnetization of 23.7 emu g−1. The electrochemical properties of the microspheres were also examined by cyclic voltammetry and the results showed a single reversible redox process. Room-temperature photoluminescence spectra of the microspheres exhibited a strong emission peak at 405 nm. The Brunauer−Emmett−Teller (BET) pore-size distribution maximum is about 37.4 nm that leads to efficient adsorption behavior. These microspheres were found to be an excellent high capacity adsorbent for the selective cationic dye (methylene blue) removal from contaminated water. The changes in parameters, such as contact time, temperature and concentration of adsorbate were examined to study their influence on adsorption capacity. The results obtained suggest that the microspheres can effectively adsorb methylene blue with an adsorption capacity increasing from 480 to 2160 mg g−1 as the initial concentration was increased from 50 to 400 mg L−1. Owing to the superior properties and novelty of the synthesized hybrid microspheres, they can possibly be used in several applications, e.g., in catalysis, bio-assays, and electric and magnetic devices.Download high-res image (132KB)Download full-size image

•New route of preparing inorganic nanocrystal shell on polyimide core was proposed.•The method relies on the ion-exchange and interfacial reaction.•Precise control of size, structure and constituent of inorganic shell was achieved.•A broad range of magnetic properties can be feasibly incorporated.•Serve as a benchmark for preparing core-shell/organic-inorganic composite systems.Uniform and stable core-shell microspheres composed of a polyimide (PI) core and thin metal/oxide/sulphide shells were prepared by an interfacial reaction of metal-ion-doped polymeric cores in reduction or in the air or sodium sulphide solutions, respectively. The silver shells on polyimide microspheres were prepared by the introduction of silver ions into ion-exchangeable surface-modified polyimide, and subsequently an in situ reduction of the silver ions in solution. Oxides shells such as SnO2, Co3O4, NiO, CuO or ZnO were prepared by thermally treating the ion-doped microspheres in air, while amorphous sulphides shells such as CuS, ZnS, CoS or Ag2S were prepared by an interfacial reaction of metal-ion-doped microspheres in its corresponding sodium sulphide solutions. The adhesion properties between the copper sulphide and PI substrates are demonstrated superior. This simple strategy is promising in the fabrication of a whole range of inorganic shells on polyimide microspheres, which may offer tailor-designed multi-functionalities based on the distinctive species of these inorganic shells.

Poly(aryloxy)phosphazenes emerge as an important class of hybrid polymers for a whole range of potential applications. To date, however, little is known about the detailed reaction mechanisms during preparation. This draws a great deal of attention for developing well-defined and well-controllable synthesis methods. In this paper, poly(dichlorophosphazene) (PDCP) has been successfully synthesized, and subsequent reaction with sodium phenoxide or phenol in the presence of K2CO3 can produce poly(bis(phenoxy)phosphazene) (PBPP). To elucidate the issues of branching and cross-linking, focuses have been placed on the change of various reaction conditions, in terms of concentration, temperature, time, solvent, catalysis, etc. The product polymers were examined using the techniques of 31P and 13C NMR, GPC, XPS, and FT-IR, in order to characterize the structural defects, in particular, branching and unwanted substitutions, such as addition of water molecules or oxidation of the phosphorus atoms on the backbone of the polymers. This work sheds light on the tailor design of poly(aryloxy)phosphazenes and other polyphosphazenes with more uniform and controllable structures.

•Amorphous copper sulphide was grown on polyimide films via solid–liquid interfacial reactions at room temperature.•Thermal treatment resulted in not only the in-situ transformation of amorphous copper sulphide to hexagonal CuS crystals, but also the morphologies of CuS from irregular to rectangle.•Continuous CuS layers were formed, endowing the composite films semi-conductivity.•Our methodology demonstrates a simple route to a variety of fabricating functional materials including noble metal, magnetic/dielectric, semiconducting for assembling on polymeric films with novel structure and function in nanotechnology.Copper sulphide nano-crystals were grown on polyimide films via an interfacial reaction of copper ions-doped precursors in sodium sulphide solution during which double diffusion and interfacial precipitation reaction occurred between the interfaces of the polyimide films and the aqueous surroundings. The newly formed copper sulphide was amorphous and distributed uniformly on the surfaces of polyimide films, and subsequent thermal treatment in vacuum transformed the amorphous copper sulphide to hexagonal crystals ones. The adhesion properties between the copper sulphide and PI substrates are unique and the mechanical properties of nanocomposite films are similar to their parent films because its inside is intact during the whole processes. This simple strategy might be extended to fabricate other quantum dots on polyimide films, which might show multi-functions based on the various species of the metal sulphides.

Polyimide (PI) short fiber-filled ethylenepropylenediene monomer (EPDM) insulations for a solid rocket motor were fabricated by surface modification of PI short fibers in an alkaline aqueous solution and subsequently by mixing formulation of EPDM insulations on a two-roll mill. The effects of PI short-fiber surface modification and short-fiber content on the mechanical and ablative properties were investigated. The excellent mechanical and ablative properties of PI fiber-filled EPDM insulations were based on their unique fiber/polymer adhesive property because of the rough surface character of modified PI fibers. The microstructures of char layers of the insulations were also characterized by scanning electron microscopy and energy-dispersive spectrometry.

α-Fe2O3 nanoparticles have been formed on a flexible polyimide (PI) substrate via an ion-exchange and in situ oxidation process in air, which involved doping the ferrous (Fe2+) ions into modified layers of PI films and a subsequent thermal treatment converted Fe2+ into α-Fe2O3 nanoparticles. These nanoparticles would migrate and aggregate compactly onto the surfaces, and thus form continuous layers with semi-conductivity. The phase transition of α-Fe2O3 to Fe3O4 nanolayers occurred when the PI/α-Fe2O3 composite films were heated under a continuous hydrogen/nitrogen gas flow. The effects of the thermal treatment conditions on the oxidation behaviors of Fe2+ and the micro-structures of α-Fe2O3 and Fe3O4 nanolayers were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The phase transition of α-Fe2O3 to Fe3O4 was confirmed by XRD and high-resolution transmission electron microscopy (HRTEM). Vibrating Sample Magnetometer (VSM) measurements showed that the PI/α-Fe2O3 and PI/Fe3O4 composite films presented antiferromagnetism and ferrimagnetism respectively. Both composite films maintained the excellent thermal stability and flexibility of the pure PI films.

Controllable growth of newly born silver nanoparticles to fractal, cauliflower-like, microscale disks and continuous silver layers with high conductivity and reflectivity on plastic substrates has been developed via solid–liquid interfacial reduction and growing of ion-doped polymeric films. Such approaches involve polyimide (PI) films as substrates, its corresponding silver-ion-doped precursors as solid oxidants, and facile immersion of ion-doped polymeric films in aqueous reducing solution. The solution reducing process belongs to liquid–solid interfacial reduction processes, during which silver ions doped in polymeric matrix transformed to newly born silver nanoparticles which further aggregated and migrated along the liquid–solid interface to form dendrite, cauliflower-like and lamella disk-like architecture and/or severely compact continuous silver nanolayers with highly reflective and conductive properties. Time-dependent morphology evolutions of silver particles were traced by scanning electron microscopy (SEM), atomic force microscopy (AFM), and transmission electron microscopy (TEM). This strategy can also extend to synthesis of many other metals on polymeric films while maintaining outstanding metal–polymer adhesion based on incorporation of various metal ions, and may offer an opportunity to fabricate large scale, high-output, cost-effective processes for metal patterns on flexible polymeric substrates.

Tin oxide (SnO2) nanolayers were formed on flexible polyimide (PI) substrate via direct ion-exchange and in situ oxidation process utilizing pyromellitic dianhydride/4,4′-oxidianiline-based poly(amic acid) films as polyimide precursor. During an ion-exchange process, stannous ions were doped into the precursor by immersion in ethanolic solution of stannous chloride. Subsequent thermal treatment of the tin(II)-containing precursor at a constant heating rate not only imidized poly(amic acid) to PI but also converted stannous ions into SnO2 clusters, which diffused and aggregated onto the surface of polymer matrix, forming continuous tin oxide layers. Inductively coupled plasma (ICP) was used to investigate the ion-exchange process. Changes in chemical structure of the poly(amic acid) film and the crystal structure of tin oxides were analyzed by attenuated total reflection-Fourier transform infrared (ATR-FTIR) and X-ray diffraction (XRD). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to study the microstructure of the PI/SnO2 nanocomposite films. The nanocomposite film maintained essential mechanical property and thermal stability of pristine PI films.Keywords: direct ion exchange; in situ oxidation; nanocomposite film; polyimide; tin oxide

Continuous nickel oxide (NiO) nanocomposite layer on flexible polyimide (PI) substrate was prepared via an ion exchange technique. First, nickel(Π) poly(amate) layers were formed on both surfaces of PI film through chemical surface modification of PI films in aqueous NaOH solution and then ion exchange in aqueous NiSO4 solution. Subsequently, hydrothermal treatment of the Ni2+-loaded PI films in an aqueous urea solution led to Ni(OH)2 formation in the surface-modified layers. Final thermal annealing in ambient air made Ni(OH)2 decompose to NiO, which diffused and aggregated to give continuous layers on both surfaces of PI film. The composite films were characterized by XRD, XPS, SEM, TEM, TGA, and DSC, respectively. Results from SEM and TEM measuring revealed that the NiO layers consisted of NiO nanoparticles with diameter ranging from 10 to 15 nm. Thermal properties of PI/NiO nanocomposite films were similar to those of host PI. This paper provides an effective methodology for the preparation of polymer/metal oxide nanocomposite films, which hold great promise toward the potential application in the areas of flexible microsensors and devices.Keywords: ion exchange; nanocomposites; nickel oxide; polyimide; surface modification

An easy technique is developed to fabricate highly conductive and reflective double-surface-silvered polyimide films at room temperature by the incorporation of silver ions in surface-modified polyimide, and subsequently by the in situ reduction of silver ions in alkaline containing aqueous glucose solution. Surface properties of the silvered composite films were investigated as a function of treatment time and reducing environment, respectively. Sheet reflectivity and conductivity can be controlled by adjusting the potassium hydroxide (KOH) etching and reducing conditions. The excellent silver-polymer adhesive property is based on a “tree roots” like micro/nanostructure of the silver layers. The essential mechanical properties of the silvered films were maintained as their inside matrix is intact during the whole procedure. Different properties between one film’s double-side surfaces were investigated during the fabricating process. Films were characterized by inductively coupled plasma (ICP), X-ray diffraction (XRD), contact angle (CA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), four point probe instrument, and ultraviolet (UV) spectrophotometer.