Conducting polymer hydrogels consisting of polypyrrole (PPy) and chitosan (CS) are prepared by static polymerization of pyrrole using methyl orange (MO) as the dopant and Fe2(SO4)3 as the oxidant in the CS aqueous solution. PPy/CS composite hydrogels not only have good electrical conductivities, but also exhibit excellent swelling/deswelling behaviors due to the participation of one-dimensional conducting PPy blocks in the hydrogel network. The effects of the amount of the oxidant and ionic strength on the physical properties of PPy/CS composite hydrogels are studied in detail. The results show that PPy/CS composite hydrogels have improved water absorbencies in saline solutions compared with the conventional polyelectrolyte hydrogel. 相似文献
Degradation behaviors of porous scaffolds play an important role in the engineering process of a new tissue. In this study, three-dimensional porous silk fibroin/chitosan (SFCS) scaffolds were successfully prepared by freeze-drying method. In vitro degradation behaviors of SFCS scaffolds have been systematically investigated up to 8 weeks in phosphate buffer saline (PBS) solution at 37 °C. The following properties of the scaffolds were measured as a function of degradation time: pore morphology, structure, weight loss, and wet/dry weight value. The pH value of the PBS solution during degradation was also detected. SFCS scaffolds maintained its porous structure till 6 weeks of degradation. During the first 2 weeks, the pH value fluctuated in a narrow range from 6.53 to 6.93. SFCS scaffolds degraded much more quickly during the first 2 weeks, and the weight loss reached 19.28 wt% after 8 weeks of degradation. The degradation process affects little SFCS scaffolds' swelling properties. 相似文献
Porous polycaprolactone(PCL)/chitosan(CH) scaffolds with large pore sizes and high porosities were fabricated via a particle-leaching technique using hexafluoro-2-propanol as a shared solvent and salt (sodium chloride) particles as porogen. By optimizing processing conditions, numerous PCL/CH scaffolds with CH proportion lower than 50 wt% and similar pore parameters were built. These scaffolds were further evaluated for their compressive mechanical properties and biodegradation behaviors. It was found that their compressive modulus and stress at 10% strain were basically maintained in their dry state in contrast to their individual components, and these scaffolds still showed well-defined compressive characteristics and dimension stability even in their hydrated state compared with pure chitosan scaffolds. After being exposed to PBS or enzymatic degradation systems in vitro for various periods up to 10 weeks, it was observed that degradation of the PCL component could be accelerated at various rates depending on the compositions of the scaffolds and the media, and the chiosan component could effectively buffer the acidic degradation products of the PCL component. 相似文献
Summary: The fabrication of novel conductive poly(DL ‐lactide)/chitosan/polypyrrole complex membranes is reported. Using poly(DL ‐lactide)/chitosan blends as matrices and polypyrrole as a conductive component, several kinds of membranes with various compositions are prepared. A percolation threshold of polypyrrole as low as 1.8 wt.‐% is achieved for some membranes by controlling the chitosan proportion between 40 and 50 wt.‐%. SEM images exhibit that the membranes with a low percolation threshold show a two‐phase structure which consists of poly(DL ‐lactide) and chitosan phases. Dielectric measurements indicate that there is limited miscibility between the poly(DL ‐lactide) and chitosan but polypyrrole is nearly immiscible with the other two components. Based on the structural characteristics of the membranes, the polypyrrole particles are suggested to be localized at the interface between two phases.
Dependence of conductivity of complex membranes on the PPy content. (○) PDLLA/PPy, (▪) PDLLA/ch(10)/PPy, (▵) PDLLA/ch(20)/PPy, (•) PDLLA/ch(30)/PPy, (□) PDLLA/ch(40)/PPy, and (▴) PDLLA/ch(50)‐PPy. 相似文献
Due to the massive discharge of antibiotics in water, it is an urgent matter to remove antibiotics from waste water. The photocatalysts with high stability and activity have attracted extensive attention from researchers. By an in-situ polymerization method, polypyrrole(PPy) was modified on the surface of TiO2(named as TiO2/PPy). By one-step reduction method, Ni Co P was grafted on the surface of TiO2/PPy(named as TiO2/PPy/NiCoP) to synthesize the phot... 相似文献
Biodegradable and thermosensitive poly(organophosphazenes) with various substituents were synthesized and their hydrolytic degradation properties were investigated in vitro and in vivo. The aqueous solutions of all polymers showed a sol-gel phase transition behavior depending on temperature changes. The side groups of polymers significantly affected the polymer degradation and accelerated hydrolysis of polymers in the order of carboxylic acid > depsipeptide > without carboxylic acid and depsipeptide. The increased gel strength led to the decreased hydrolysis rate. The polymer hydrogels with 750 Da of α-amino-ω-methoxy poly(ethylene glycol) were rapidly decreased by dissolution. The polymer degradation was also influenced by pH and temperature. The in vivo behaviors of mass decrease of the polymer hydrogels were similar with the in vitro results. These results suggest that the biodegradable and thermosensitive poly(organophosphazenes) hold great potentials as an injectable and biodegradable hydrogel for biomedical applications with controllable degradation rate. 相似文献
Polypyrrole-modified graphitic carbon nitride composites (PPy/g-C3N4) are fabricated using an in-situ polymerization method to improve the visible light photocatalytic activity of g-C3N4. The PPy/g-C3N4 is applied to the photocatalytic degradation of methylene blue (MB) under visible light irradiation. Various characterization techniques are employed to investigate the relationship between the structural properties and photoactivities of the as-prepared composites. Results show that the specific surface area of the PPy/g-C3N4 composites increases upon assembly of the amorphous PPy nanoparticles on the g-C3N4 surface. Owing to the strong conductivity, the PPy can be used as a transition channel for electrons to move onto the g-C3N4 surface, thus inhibiting the recombination of photogenerated carriers of g-C3N4 and improving the photocatalytic performance. The elevated light adsorption of PPy/g-C3N4 composites is attributed to the strong absorption coefficient of PPy. The composite containing 0.75 wt% PPy exhibits a photocatalytic efficiency that is 3 times higher than that of g-C3N4 in 2 h. Moreover, the degradation kinetics follow a pseudo-first-order model. A detailed photocatalytic mechanism is proposed with ·OH and ·O2? radicals as the main reactive species. The present work provides new insights into the mechanistic understanding of PPy in PPy/g-C3N4 composites for environmental applications. 相似文献
Degradable behaviors of polymer for implantation in body should be evaluated before clinical application. The effect of continuous mechanical load on the degradation progress of poly(d,l-lactic acid) (PDLLA) foam gasket was investigated in detail by specially designed load-providing devices. While PDLLA degraded in the PBS solution (pH, 7.4) at 37 °C for 3 months, the changes of surface morphology, molecular weight, elastic modulus, tensile strength and mass loss were recorded. The results revealed that the degradation rates of PDLLA under continuous loads were obviously quicker than those without load. Moreover, the influence of tensile plus compressive load was larger than that of tensile load. It was indicated that in vivo degradation of PDLLA would not only be influenced by the local solution, but also by the surrounding load. When regulating the degradation rate of bioabsorbable polymer, one should consider the indispensable effect of load where implanted. 相似文献
Rechargeable lithium-ion batteries (LIBs) have been the most commonly used batteries in the portable electronics market for many years. Polypyrrole (PPy) was now investigated as a conducting addition agent to enhance the cathode and anode materials performance in LIBs. Actual development in the synthesis and modification of the most promising cathode materials, LiFePO4, is described in this mini-review. The main aim of this mini-review is to highlight the effect of PPy based conducting polymer films on the electrochemical efficiency of LiFePO4 based cathode materials for LIBs summarizing our own research. Influence of the polyethylene glycol (PEG) additive in the PPy coating layer was evaluated. The improved electrochemical performance can be attributed to the enhanced electronic conductivity, higher solubility of ions originating from the electrolyte, higher movability of dissolved Li+ ions, and improved structural flexibility resulting from the incorporation of the PPy or PPy/PEG conducting polymer layer. The stabilizing effect of PEG in PPy was reflected in lowered cross-linking and reduced structural defects and, in consequence, in higher specific capacity of PPy/PEG-LiFePO4 cathodes compared to that of PPy-LiFePO4 cathodes and bare LiFePO4 cathodes. 相似文献
Abstract In this paper, a series of porous nanohydroxyapatite/silk fibroin/chitosan (nHA/SF/CTS) scaffolds were successfully prepared using the freeze-drying method. The biomaterials were characterized by attenuated total reflection Fourier transform infrared spectroscopy, and mechanical testing and thermogravimetric analysis. Moreover, studies of porosity, pore size, swelling properties and in vitro degradation test were performed. Research has proved that micro-structure, porosity, water adsorption and compressive strength were greatly affected by the components’ concentration, in particular the content of silk fibroin. SEM observations showed that the scaffolds of nHA/SF/CTS are highly porous, with pore size in wide range from 25 to 300?µm which is suitable for cell growth. nHA/SF/CTS scaffolds have sufficient mechanical integrity to resist handling during implantation and in vivo loading. Both, the compressive modulus and compressive strength of the scaffold, decrease with the increase in silk fibroin content. 相似文献
Novel flexible NH3 gas sensors were formed by the in situ self-assembly of polypyrrole (PPy) on plastic substrates. A negatively charged substrate was prepared by the formation of an organic monolayer (3-mercapto-1-propanesulfonic acid sodium salt—MPS) on a polyester (PET) substrate using a pair of comb-like Au electrodes. Two-cycle poly(4-styrenesulfonic acid) sodium salt/poly(allylamine hydrochloride) (PSS/PAH) bilayers (precursor layer) were then layer-by-layer (LBL) deposited on an MPS-modified substrate. Finally, a monolayer of PPy self-assembled in situ and PPy multilayer thin films self-assembled LBL in situ on a (PSS/PAH)2/MPS/Au/Cr/PET substrate. The thin films were analyzed by atomic force microscopy (AFM). The effects of the precursor layer (PSS), the deposition time of the monolayer of PPy and the number of PPy multilayers on the gas sensing properties (response) and the flexibility of the sensors were investigated to optimize the fabrication of the film. Additionally, other sensing properties such as sensing linearity, reproducibility, response and recovery times, as well as cross-sensitivity effects were studied. The flexible NH3 gas sensor exhibited a strong response that was comparable to or even greater than that of sensors that were fabricated on rigid substrate at room temperature. 相似文献
Unique nanocomposites of polypyrrole/Au and polypyrrole/Pt hybrid nanotubes are synthesized employing polypyrrole (PPy) nanotubes as an advanced support by solution reduction. The conducting polymer PPy nanotubes are fabricated by using pre‐prepared MnO2 nanowires as the reactive templates. MnO2 nanowires induce the 1D polymerization of pyrrole monomers and the simultaneous dissolution of the templates affords the hollow tube‐like structure. The loading content of metal nanoparticles in the nanocomposites could be adjusted by simply changing the amount of metal precursors. This work provides an efficient approach to fabricate an important kind of metal/conducting polymer hybrid nanotubes that are potentially useful for electrocatalyst and sensor materials. 相似文献
N-Succinyl chitosan (N-SC) products with various degrees of substitution were synthesized by a direct reaction between chitosan and succinic anhydride. The susceptibility of the as-synthesized polymers to degradation upon their exposure to γ-ray radiation was investigated. The results were compared with the as-received chitosan. The size exclusion chromatographic results showed that chitosan and N-SC products in their dilute aqueous solution state were more subservient to degradation by γ-ray radiation than in their solid film state, despite the much less exposure to the radiation (i.e., 5-30 kGy for the solutions versus 20-100 kGy for the films). Increasing the radiation dose resulted in the rather monotonous decrease in the molecular weights of the polymers. Structural analyses of the irradiated polymers by Fourier-transformed infrared spectroscopy (FT-IR) and UV-visible spectrophotometry indicated the increase in the amount of carbonyl groups with the radiation dose. The formation of the carbonyl groups suggested that the radiolysis of chitosan and N-SC products occurred at the glycosidic linkages. In addition, FT-IR, elemental analysis and proton nuclear magnetic resonance spectroscopy (1H NMR) results suggested that γ-ray radiation affected both the N-acetyl and N-substituted groups on the polymer chains. 相似文献
PPy@TS nanocomposite with enhanced photocatalytic capability was prepared by in situ polymerizing polypyrrole on the surface of TiO2/SiO2 nanofibrous membrane. 相似文献
A novel method for producing asymmetric membranes based on conducting polymers is described. Two layers of different polypyrrole films (PPy–p-toluene sulphonate and PPy–dodecyl sulphate) were electrodeposited onto an electrode to form a sandwich or layer structure. The films produced could be removed from the electrode and had sufficiently good mechanical properties to be used as free-standing membranes in simple transport experiments. Using electrochemically induced transport utilising technology described previously it was shown that a highly asymmetric membrane had been formed with a ratio of up to 35:1 in terms of the flux in one direction compared with another. This was for the transport of simple salts such as KCl and NaCl. In mixtures of these salts it was still possible to derive some reasonable selectivity between cations with selectivity of K+ over Na+ in ratios up to 4.5:1. 相似文献
In this work, multi-wall carbon nanotubes coated with polypyrrole (PPy/MWCNT) have been used as counter electrode (CE) materials for dye-sensitized solar cells (DSSCs). PPy was deposited onto fluorine-doped tin-oxide-coated glass by electrochemical polymerization of pyrrole. Three surfactants were used in the preparation of the hybrids: cationic cetyltrimethylammonium bromide, anionic sodium dodecylbenzenesulfonate (DBSNa), and non-ionic polyoxyethylene sorbitan monolaurate (Tween20). The morphologies of the PPy and PPy/MWCNT hybrids were investigated using scanning electron spectroscopy. Chemical composition of the prepared CEs was determined by X-ray photoelectron spectroscopy and Fourier-transformed infrared spectroscopy. The catalytic activity of the PPy and PPy/MWCNT layers was evaluated using cyclic voltammetry, and the photovoltaic properties of DSSCs with PPy and PPy/MWCNT CEs were characterized using I–V measurements. PPy/MWCNT samples that were prepared by electrochemical polymerization showed the best results when the anionic surfactant DBSNa was used during polymerization. The photoelectric conversion efficiency of PPy/MWCNT prepared by electrochemical polymerization was 2.9%, which was 59% of that of Pt CE (4.9%). 相似文献