共查询到20条相似文献,搜索用时 15 毫秒
1.
《Journal of Industrial and Engineering Chemistry》2014,20(2):397-404
Blend microspheres of cellulose triacetate (CTA) and bee wax (BW) were prepared by oil-in-water (o/w) emulsion/solvent evaporation method for investigating the controlled release (CR) of nateglinide (NTG), an antidiabetic drug with a plasma half-life of 1.5 h. The novel carrier was analyzed for surface morphology, particle size, drug–polymer interactions, physical state of the encapsulated drug and micromeritic properties. In vitro release experiments were performed in simulated gastric (pH 1.2) and intestinal pH (7.4) media that was affected by blend composition and initial drug loading. In vitro release data were analyzed by empirical equations to understand the release profile of NTG 相似文献
2.
Jesús López-Palacios Emma Muñoz M. Aránzazu Heras Álvaro Colina Virginia Ruiz 《Electrochimica acta》2006,52(1):234-239
Degradation of polyaniline films electrodeposited on optically transparent gold electrodes has been followed by thin-layer bidimensional spectroelectrochemistry. The influence of the anodic potential reached during multiple potential scans has been assessed. Correlation of changes in the spectral signals in normal and parallel arrangement has enabled identifying species of different nature, both soluble and insoluble, electroactive and inert, during the degradation of the polymer film. The three bidimensional spectroelectrochemistry signals have demonstrated the occurrence of different types of degradation processes depending on the applied potential, ranging from the simple release of oligomers and hydrolysis products retained in the film during electropolymerization to more dramatic modifications of the film. 相似文献
3.
Effect of cellulose acetate/cellulose triacetate ratio on reverse osmosis blend membrane performance
Yasmeen Elkony El-Sayed Mansour Amel Elhusseiny Shaker Ebrahim 《Polymer Engineering and Science》2020,60(11):2852-2863
Surface functionalization and modification including the grafting process are effective approaches to improve and enhance the reverse osmosis (RO) membrane performance. This work is aimed to synthesize grafted/crosslinked cellulose acetate (CA)/cellulose triacetate (CTA) blend RO membranes using N-isopropylacrylamide (N-IPAAm) as a monomer and N,N-methylene bisacrylamide (MBAAm) as a crosslinker. The morphology of these membranes was analyzed by scanning electron microscopy and their surface roughness was characterized by atomic force microscopy. The performance of these membranes was evaluated through measuring two major parameters of salt rejection and water flux using RO unit at variable operating pressures. It was noted that the surface average roughness obviously decreased from 148 nm for the pure CA/CTA blend membrane with 2.5% CTA to 110 nm and 87 nm for the grafted N-IPAAm and grafted/crosslinked N-IPAAM/MBAAm/CA/CTA-RO membranes, respectively. Moreover, the contact angle decreased from 51.98° to 47.6° and 43.8° after the grafting and crosslinking process. The salt rejection of the grafted CA/CTA-RO membrane by 0.1% N-IPAAm produced the highest value of 98.12% and the water flux was 3.29 L/m2h at 10 bar. 相似文献
4.
Qingli Hao Wu Lei Xifeng Xia Zhenzhen Yan Xujie Yang Lude Lu Xin Wang 《Electrochimica acta》2010,55(3):632-640
Mobile counter anion exchange of electropolymerized polyaniline (PANI) films with the anions in acid solutions has been investigated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), scanning electron microscopy, Raman, UV-vis, and fluorescence spectra. The studied acids include camphorsulfonic acid, p-toluene sulfonic acid, HCl, HClO4, H2SO4 and H3PO4. In two cases of small and large counter ions of PANI films, CV tests have been performed alternately three times in each of two electrolytes containing organic or inorganic acid. The investigation of electrochemical and spectrophotometric measurements reveals that large counter anions can be easily replaced by the small anions; and the reverse exchange also occurs, but shows very low efficiency. This indicates that the achieved anion exchange in both cases leads to the remarkable alteration in electrochemical behavior and electrical conductance of PANI films. This implies counter anions, whatever the original or redoping ones, play an important role in the electrical, electrochemical, even optical properties of PANI. However, the polymer morphology does not be changed after exchange tests. This allows us to point out a ‘morphology-memory’ effect which is very significant for the development and application of PANI films with the same morphology and different properties. 相似文献
5.
Shogo Nobukawa Hikaru Shimada Yoshihiko Aoki Azusa Miyagawa Vu Ahn Doan Hiroshi Yoshimura Yutaka Tachikawa Masayuki Yamaguchi 《Polymer》2014
We examined birefringence in a stretched film of cellulose triacetate (CTA) after extraction of an immiscible component. The CTA film plasticized by di(2-ethylhexyl) adipate (DOA), which was added as the immiscible additive, exhibited negative birefringence to the same degree as the pure CTA film. Following removal of DOA from the film by immersion into methanol, the birefringence of the blend film changed dramatically from negative to positive. Moreover, the wavelength dependence also changed from ordinary to extraordinary, in which the absolute value of birefringence increases with wavelength. Scanning electron microscope (SEM) images revealed nanoscale ellipsoidal pores in the film after the extraction, suggesting that DOA was segregated and formed ellipsoidal domains in the CTA matrix during annealing and stretching. According to an optical theory for the nanoporous structure, we found that the form birefringence contributes to control of the optical properties of the CTA film. This phenomenon could be utilized in the design of high-performance optical films, such as quarter waveplate, because sign and wavelength dispersion of birefringence can be controlled even for a single component film. 相似文献
6.
Nanocomposite of polyaniline (PANI) with natural clinoptilolite (Clino) was prepared. Formation of nanocomposite and incorporation of polyaniline in the clinoptilolite channels was confirmed and characterized using FTIR spectroscopy studies, X-ray diffraction (XRD) pattern, scanning electron microscopy (SEM) and cyclic voltammetry techniques. The anticorrosive properties of a 20 μm thickness coating of PANI/Clino nanocomposite with various weight ratios (1, 3 and 5%, w/w) of clinoptilolite content on iron coupons was evaluated and compared with pure polyaniline coating. According to the results in acidic environments PANI/Clino nanocomposite has enhanced corrosion protection effect in comparison to pure polyaniline coating. Comparative experiments revealed that PANI/Clino nanocomposite with 3% (w/w) clinoptilolite content has the best protective properties. Further experiments showed that the PANI/Clino nanocomposite has considerably different corrosion protection efficiencies in various corrosive environments. 相似文献
7.
Marisa Sheffer 《Electrochimica acta》2009,54(11):2951-2299
Local and bulk deposition of gold particles was accomplished by the spontaneous reaction between chemically reduced polyaniline (PAN) thin films and AuCl4− ions. PAN layers were electrodeposited on glassy carbon (GC). Characterization of the PAN films was carried out by microscopy and electrochemistry. Local deposition of gold particles was performed by means of scanning electrochemical microscopy, where a gold microelectrode was used to produce a flux of gold ions in close vicinity to an unbiased PAN film. We found that the nature of the gold particles was greatly affected by the potential applied at the microelectrode as well as the oxidation state of the PAN films. 相似文献
8.
Solutions of cellulose triacetate (CTA) in trifluoroacetic acid (TFA) become liquid crystalline above a certain critical concentration. Using the techniques of spectrophotometry, wide-angle light scattering and circular dichroism we have shown that the mesophase formed is cholesteric. We have measured its pitch, which depends on polymer concentration, and shown that the cholesteric structure is right-handed. Measurements of optical activity and the optical effects of shear and magnetic fields are also described and discussed. 相似文献
9.
For the elucidation of the crystal structures of the two crystalline allomorphs of cellulose triacetate (CTA), namely CTA I and CTA II, two-dimensional (2D) solid-state through-bond 13C-13C and 1H-13C correlations NMR techniques applied to the two crystalline allomorphs of CTA. As a result, the 13C and 1H chemical shifts of the glucopyranose ring of CTA I and CTA II were completely assigned by the 2D NMR spectra of these allomorphs. On the 2D 13C-13C correlation spectrum of CTA II, two sets of the 13C-13C correlations from C1 to C6 were observed. This indicated that the CP/MAS 13C NMR spectrum of CTA II can be characterized by its overlapping of the 13C subspectra of two kinds of 2,3,6-triacetyl-anhydroglucopyranose units and that there are two magnetically non-equivalent sites in the unit cell of CTA II. In the case of CTA I, the numbers of respective 13C and 1H shifts of CTA I agreed with the those of the glucopyranose residue in the allomorph, strongly suggesting that the asymmetric unit of CTA I is only one glucose residue. In addition, conformational differences in the exocyclic C5-C6 bonds between CTA I and CTA II were strongly suggested by the notable differences in the 1H and 13C chemical shifts at the C6 sites of these allomorphs. 相似文献
10.
The thermal discharge behaviour of cellulose diacetate (CA2) (39% acetyl content) and cellulose triacetate (CA3) (44% acetyl content) films was studied at different polarizing temperatures and fields. Cellulose diacetate exhibited two peaks, one at low temperatures and the other at high temperatures, whereas cellulose triacetate exhibited only one peak. The origin of these peaks in CA2 is attributed to dipolar orientation and space charge polarization respectively, while the only peak in CA3 is due to space charge polarization. The difference in thermal discharge behaviour of CA2 and CA3 is attributed to the difference in acetyl contents of the two acetates. 相似文献
11.
以三乙酸纤维素(CTA)为膜材料,1,4-二氧六环、丙酮为溶剂,甲醇、乳酸为添加剂,采用相转换法制备了三乙酸纤维素正渗透膜。研究了不同1,4-二氧六环/丙酮配比、添加剂乳酸含量、挥发时间、膜厚度、热处理温度条件下正渗透膜性能的变化规律。研究表明,当采用纯水为原料液,0.56mol/L CaCl2为汲取液时,优化制备的CTA正渗透膜的水通量达到14.10L/(m2?h),溶质反扩散量为0.031mol/(m2?h);采用0.1mol/L NaCl为原料液,4mol/L葡萄糖为汲取液时,优化制备的CTA正渗透膜的水通量保持在5L/(m2?h)以上,对NaCl的截留率大于99%。CTA正渗透膜相比于HTI膜,具有较高的亲水性、水通量、截留率,稳定性更好。 相似文献
12.
We have studied electrochemical matrix polymerization of aniline in the presence of poly(amidosulfonic acid)s of different nature: poly(2-acrylamido-2-methyl-1-propanosulfonic acid) (PAMPSA, flexible backbone); poly(p,p′-(2,2′-disulfoacid)-diphenylene-iso-phthalamid) (i-PASA, semi-rigid backbone); poly(p,p′-(2,2′-disulfoacid)-diphelylene-tere-phthalamid) (t-PASA, rigid backbone). Also, we have investigated spectral and electrochemical properties of the films obtained, as well as their surface morphology. The matrix polymerization results in the formation of interpolymer complexes of polyaniline (PANI) and the above-cited polyacids. The acceleration of aniline electropolymerization in the presence of poly(amidosulfonic acid)s was observed due to association of aniline molecules to sulfonic groups of the polyacid and higher local concentration of protons near the polyacid backbone. The rigid-chain polyacids interfere with the normal course of the electropolymerization, which manifests itself in the changes of the shape of time dependences of absorbance and charge. Cyclic voltammetry and spectroelectrochemical experiments showed that the formation of interpolymer complex with rigid-chain polyacids distorts spectroelectrochemical characteristics of PANI. This evidently results from steric hindrances in the formation of quinoid units. 相似文献
13.
Cellulose triacetate (CTA) ultrafiltration membranes were prepared via phase inversion technique using hydrophilic TEMPO-oxidized cellulose nanofibrils (TOCNs) as modifying agents. The permeation performance of the prepared membranes was evaluated in terms of pure water flux (Ji), protein rejection (Rm) and flux recovery ratio (FRR). Membrane surface morphology and cross-sectional structures were characterized by atomic-force microscopy (AFM) and scanning electron microscopy (SEM), respectively. XRD was performed in order to investigate the interactions between membrane components. Meanwhile, the effects of TOCN concentration on hydrophilicity of the membrane surface and mechanical properties were also examined. The experimental results indicated that CTA/TOCN composite membranes exhibit significant differences in surface properties and intrinsic properties due to the addition of TOCNs. 相似文献
14.
Carla Dalmolin Sonia R. Biaggio Romeu C. Rocha-Filho Nerilso Bocchi 《Electrochimica acta》2009,55(1):227-233
Polyaniline was electrodeposited onto reticulated vitreous carbon – RVC – in order to obtain a tridimensional composite electrode. Three variations of these electrodes were analysed: a small-anion-doped polyaniline (RVC/Pani), a polyanion-doped polyaniline (RVC/PaniPSS) and a bi-layer type formed by an inner layer of the first electrode and an outer layer of the second one (RVC/Pani/PaniPSS). These composites were characterized by cyclic voltammetry, scanning electronic microscopy and electrochemical impedance spectroscopy. Photomicrographies, voltammetric profiles and impedance data pointed to different morphological and electrochemical characteristics for polyaniline doped with small or large anions, and a mixed behavior for the bi-layer electrodes. Charge–discharge tests for these tridimensional (3D) electrodes, employed as the cathode in lithium batteries, indicated better performance for the RVC/Pani electrode. These RVC composites presented higher specific capacities when compared with those obtained for Pani deposited onto bidimensional substrates. 相似文献
15.
Nanocomposites of polyaniline (PANI) with organophilic montmorillonite (O-MMT) and hydrophilic montmorillonite (Na-MMT) were prepared. The nanocomposites were characterized using FT-IR, D.C. electrical conductivity measurement and cyclic voltammetry techniques. It was found that PANI/Na-MMT nanocomposite has lower (5.8%) and PANI/O-MMT nanocomposite has higher (29.4%) conductivity compared to pure polyaniline. Cyclic voltammetry experiments showed that both nanocomposites are electroactive. The anticorrosive properties of a 100 μm thickness coating of nanocomposites on iron coupons were evaluated and compared with pure polyaniline coating. According to the results PANI/MMT nanocomposites have enhanced corrosion protection effect in comparison to pure polyaniline coating. Results showed also that the PANI/Na-MMT and PANI/O-MMT nanocomposites have considerably different corrosion protection efficiencies in various corrosive environments. 相似文献
16.
Carlos Alemán Carlos A. Ferreira Alvaro Meneguzzi Marco A.S. Rodrigues 《Polymer》2008,49(23):5169-5176
A comprehensive study about the molecular and electronic properties of the different forms of polyaniline has been developed using quantum mechanical calculations. Initially the performance of different ab initio and DFT quantum mechanical methods has been evaluated by comparing the results provided for small model compounds containing two repeating units. After this, calculations on the emeraldine base, leucoemeraldine base, pernigraniline base and emeraldine salt (monocationic and dicationic) forms of oligoanilines with n repeating units, where n ranged from 5 to 13, have been performed using the BH&H/6-31G(d) method, which was found to be a very suitable theoretical procedure. Interestingly, calculations indicate that the distribution in blocks of the repeating units containing amine and imine nitrogen is largely preferred for the emeraldine base form. On the other hand, the molecular structure and band gap of the emeraldine base, leucoemeraldine base and pernigraniline base forms have been rationalized according to their differences in the conjugation of the C6H4 rings. Calculations on cationic oligoanilines indicate that, when the emeraldine salt form presents a doublet electronic state, the positive charge and the spin density are located in the middle of the chain extending through five consecutive repeating units. 相似文献
17.
《Progress in Polymer Science》2013,38(9):1287-1306
Polyaniline (PANI) has been the subject of considerable recent interest because of their unique electrical behavior, good environmental stability in doped and neutral states, ease of synthesis and wide applications in different fields. However, the main drawback of PANI is lack of solubility, which explains its limited processability due to a rigid backbone. Various procedures have been adapted to improve its processability. The major part of this review is a discussion of some of the methods employed for chemical modification of PANI, including doping via Acid–Base chemistry, sulfonation of PANI or copolymerization of aniline with sulfonated aniline derivatives, synthesis of PANI composites with processable polymers, copolymerization of aniline with substituted corresponding monomers, incorporation of polymeric chains or long and flexible alkyl chains in the PANI backbone, and enzymatic polymerization of aniline during the last decade. 相似文献
18.
Shaker Mabrouk Ebrahim 《Journal of Polymer Research》2009,16(5):481-487
The electrical properties, including current-voltage (I-V) and capacitance-voltage (C-V) characteristics, of ITO/polyaniline/Al
and ITO/polyaniline/Zn Schottky diodes have been investigated. Polyaniline (PANI) was prepared chemically and doped with 2-acrylamido-2-methyl-1-propanesulfonic
acid sodium salt (AMPSNa). The maximum conductivity value for PANI-AMPSNa films was 1.8 × 10−2 S/cm at 0.5 weight ratio of AMPSNa. The values of various junction parameters such as ideality factor, barrier height and
charge carrier concentration were calculated based on the thermionic emission theory. Zn electrode showed better rectifying
behavior with PANI-AMPSNa film than Al electrode. The obtained C-V characteristics showed that the charge carrier concentration
is in the range of 1016/cm3. 相似文献
19.
In this paper, electrical and dielectric properties of multiwall carbon nanotubes (MWCNTs)/insulating polyaniline (PANI) composites
were studied. A mixture of MWCNTs and insulating polyaniline was dispersed in an ethanol solution by ultrasonic process, subsequently
dried, and was hot-pressed at 200 °C under 30 MPa. Electrical and dielectric properties of the composites were measured. The
experimental results show that the dc conductivities of the composites exhibit a typical percolation behavior with a low percolation
threshold of 5.85 wt.% MWCNTs content. The dielectric constant of the composites increases remarkably with the increasing
MWCNTs concentration, when the MWCNTs concentration was close to percolation threshold. This may be attributed to the critical
behavior of the dielectric constant near the percolation threshold as well as to the polarization effects between the clusters
inside the composites. 相似文献
20.
Roya Kabiri 《国际聚合物材料杂志》2016,65(13):675-682
A series of conductive nanocomposites cellulose/reduced graphene oxide/polyaniline (cellulose/RGO/PANi) were synthesized via in situ oxidative polymerization of aniline on cellulose/RGO with different RGO loading to study the effect of RGO on the properties of nanocomposites. The results showed that when RGO is inserted into cellulose/PANi structure, its thermal stability and conductivity are increased. So that adding of only 0.3 wt% RGO into the cellulose/PANi structure, its conductivity is increased from 1.1 × 1 10?1 to 5.2 × 110?1 S/cm. Scanning electron microscopy results showed that the PANi nanoparticles are formed a continuous spherical shape over the cellulose/RGO template; this increases the thermal stability of nanocomposite. 相似文献