Electrochemical polymerization of aniline in the presence of poly(acrylic acid) and characterization of the resulting films

Conducting films composed of polyaniline (PANI) and poly(acrylic acid) (PAA) were prepared by electrochemical polymerization of aniline in the presence of PAA. The PAA content in the films (PANI/PAA films) was controlled by the concentration of PAA in polymerization solution, and the properties of the films were investigated in relation to the PAA content. It was demonstrated by means of scanning electron microscopy and cyclic voltammetry that the surface morphology and electrochemical property of the films were affected significantly by the PAA content. In contrast, the conductivity of the films was found hardly dependent on the PAA content up to 18 wt %. The cyclic voltammetry gave an interesting result that the PANI/PAA films showed an electroactivity in neutral solution, which was not observed for the PANI film without PAA, and the electroactivity was closely related to the PAA content in the PANI/PAA films.     

不同工艺对PANI/PAA复合薄膜的电致变色性能影响研究

采用直接聚合法与逐层镀膜法分别成功制备了聚苯胺(PANI)/聚丙烯酸(PAA)复合薄膜,通过扫描电镜(SEM)、傅里叶变换红外光谱(FT-IR)等方法考察了两种工艺制备的薄膜的形貌和微结构,并测定了两种复合薄膜的循环伏安性能(CV)、电流响应特性(CA)及电致变色性能。结果表明,SEM与FT-IR证实了两种方法制备的PANI/PAA复合薄膜仅在材料结构上有所不同;直接聚合法制备的PANI/PAA复合薄膜(PANI/PAA-DP)表面具有较大颗粒,2对明显的氧化还原峰,氧化态和还原态的响应时间分别为120ms和226ms,在600~700nm波长处的透过率调制幅度为10%;逐层镀膜法制备的PANI/PAA复合薄膜(PANI/PAA-LP)具有多孔的网络结构,3对氧化还原峰,氧化还原反应更明显,电致变色性能更优异,其氧化态和还原态的响应时间分别为45ms和67ms,在600~700nm波长处的透过率调制幅度可达40%。     

不同工艺对PANI/PAA复合薄膜的电致变色性能影响

采用直接聚合法与逐层镀膜法分别成功制备了聚苯胺(PANI)/聚丙烯酸(PAA)复合薄膜,通过SEM、FTIR考察了两种工艺制备的薄膜的形貌和微结构,并测定了两种复合薄膜的循环伏安性能(CV)、电流响应特性(CA)及电致变色性能。结果表明,SEM与FTIR证实了两种方法制备的PANI/PAA复合薄膜仅在材料结构上有所不同;直接聚合法制备的PANI/PAA复合薄膜(PANI/PAA-DP)表面具有较大颗粒,两对明显的氧化还原峰,氧化态和还原态的响应时间分别为120 ms和226 ms,在600～700 nm波长处的透过率调制幅度为10%;逐层镀膜法制备的PANI/PAA复合薄膜(PANI/PAA-LP)具有多孔的网络结构,3对氧化还原峰,氧化还原反应更明显,电致变色性能更优异,其氧化态和还原态的响应时间分别为45 ms和67 ms,在600～700 nm波长处的透过率调制幅度可达40%。     

Layer-by-layer assembly of polyaniline nanofibers/poly(acrylic acid) multilayer film and electrochemical sensing

Polyaniline (PANI) nanofibers are synthesized by dilute polymerization and subsequently used for layer-by-layer assembly with poly(acrylic acid) (PAA). The chemical synthesized PANI nanofibers are characterized by SEM and TEM. In addition, the LBL assembly process is characterized by SEM, UV-vis spectrometry and electrochemical methods. PAA inside the multilayer film can dope nanostructured PANI effectively and shift its electroactivity to a neutral pH environment. Compared with PANI/PAA film co-deposited on the electrode by electropolymerization, the redox behavior of PANI/PAA multilayer via LBL assembly is more reversible, indicating the enhancement of electron transfer. The obtained nanostructured PANI/PAA multilayer films are very stable and show high electrocatalytic ability toward H₂O₂, which makes it an ideal substrate for H₂O₂ detection and offers great promise for biosensing.     

Preparation and electroactivity of polyaniline/poly(acrylic acid) film electrodes modified by platinum microparticles

The preparation and properties of poly(acrylic acid) (PAA)-doped polyaniline (PANI) film electrodes further modified by electrodeposition of platinum particles were investigated by cyclic voltammetry and in situ conductivity measurement. The PANI/PAA film exhibits a better electroactivity and higher stability, even in solutions of lower acidity, although its polymerization rate is decreased three-fold compared to that of PANI. The conductivity of the PANI/PAA film increases by a factor of two compared to that of PANI. The effects of the carboxylic acid groups of PAA in the PANI matrix on the performance of the film are discussed. The electrocatalytic activity of PANI/PAA/Pt for reduction of hydrogen and oxidation of MeOH is higher than that of PANI modified with Pt particles alone. Characterization of the electrodes by SEM shows the platinum modification procedure yields roughly spherical catalyst particles 0.51mum in diameter dispersed throughout the polyaniline.     

Preparation and electroactivity of polyaniline/poly(acrylic acid) film electrodes modified by platinum microparticles

The preparation and properties of poly(acrylic acid) (PAA)-doped polyaniline (PANI) film electrodes further modified by electrodeposition of platinum particles were investigated by cyclic voltammetry and in situ conductivity measurement. The PANI/PAA film exhibits a better electroactivity and higher stability, even in solutions of lower acidity, although its polymerization rate is decreased three-fold compared to that of PANI. The conductivity of the PANI/PAA film increases by a factor of two compared to that of PANI. The effects of the carboxylic acid groups of PAA in the PANI matrix on the performance of the film are discussed. The electrocatalytic activity of PANI/PAA/Pt for reduction of hydrogen and oxidation of MeOH is higher than that of PANI modified with Pt particles alone. Characterization of the electrodes by SEM shows the platinum modification procedure yields roughly spherical catalyst particles 0.51mum in diameter dispersed throughout the polyaniline.     

Oxidative graft polymerization of aniline on the modified surface of polypropylene films

A novel method for preparing electrically conductive polypropylene‐graft‐polyacrylic acid/polyaniline (PP‐g‐PAA/PANI) composite films was developed. 1,4‐Phenylenediamine (PDA) was introduced on the surface of PP‐g‐PAA film, and then, chemical oxidative polymerization of aniline on PP‐g‐PAA/PDA film was carried out to prepare PP‐g‐PAA/PANI electrically conductive composite films. After each step of reaction, the PP film surface was characterized by attenuated total reflectance Fourier transform infrared spectroscopy. Static water contact angles of the PP, PP‐g‐PAA, and PP‐g‐PAA/PANI films were measured, and the results revealed that graft reactions took place as expected. The morphology of the PP‐g‐PAA film and the PP‐g‐PAA/PANI composite film were observed by atomic force microscopy. The conductivity and the thickness of the PP‐g‐PAA/PANI composite films with 1.5 wt % PANI were around 0.21 S/cm and 0.4 μm, respectively. The PANI on the PP‐g‐PAA/PANI film was reactivated and chain growing occurred to further improve the molecular weight of PANI. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2442–2450, 2007     

Synthesis of fully and partially sulfonated polyanilines derived from ortanilic acid: An electrochemical and electromicrogravimetric study

The electrochemical polymerization of 2-aminobenzene sulfonic acid, also called ortanilic acid (o-ASA), on a gold electrode precoated with polyaniline (PANI), has been carried out. We proved that the electropolymerization of o-ASA is enhanced on PANI electrodes, resulting in thicker films obtained in aqueous media at room temperature. The electrosynthesized film (P(o-ASA)) was characterized by cyclic voltammetry, FTIR and nuclear magnetic resonance. The compensation of P(o-ASA) charge was evaluated using electrochemical quartz crystal microbalance combined with cyclic voltammetry, which showed that the electroneutralization process mainly involves cations. Additionally, copolymers of aniline and o-ASA were electrosynthesized, using a metallic electrode modified with PANI also as a working electrode. The degree of sulfanation of copolymers has been modulated with the proportions of monomers in the electrosynthesis solution. The studies reveal a more important participation of cations in fully sulfonated polyaniline than in partially sulfonated polyaniline.     

Comparison of the growth process and electrochemical properties of polyaniline films prepared by pulse potentiostatic and potentiostatic method on titanium electrode

Polyaniline (PANI) films were deposited on titanium (Ti) electrode in a bath containing 0.3 mol L^?1 aniline and 1 mol L^?1 HNO₃ by pulse potentiostatic method (PPM) and potentiostatic method (PM). The chronoamperograms during aniline polymerization were recorded, and the morphologies of PANI films prepared with different polymerization periods were examined under scanning electron microscope. The difference between the processes of PANI films growth was studied. The growth processes of PANI films prepared by PPM and PM are divided into two stages. For both PPM and PM, the first stage corresponds to the formation of a compact granular PANI layer on the surface of Ti electrode. The second stage corresponds to further growth of PANI film on the surface of the compact granular PANI film. However, the PANI films prepared by PPM and PM show different morphologies in this stage. In addition, the electrochemical properties of the PANI films prepared by PPM and PM are obviously different. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 458–463, 2007     

Processable conductive blends of polyaniline/polyimide

By using camphorsulfonic acid (CSA) to protonate polyaniline (PANI), the counterion enabled the PANI–CSA complex processable as a solution phase. So camphorsulfonic acid (CSA)-doped polyaniline/polyimide (PANI/PI) blend films were prepared by the solvent casting method using N-methylpyrrolidinone (NMP) as a cosolvent followed by thermal imidization. The conductivity of the PANI–CSA/PAA (50 wt % PANI content) is greater than that of the pure PANI sample at room temperature. As the thermal imidization proceeded, molecular order of polymer chain structure was improved in the resulting PANI–CSA/PI film due to the annealing effect of PANI chain, and this PANI–CSA/PI film showed higher conductivity than PANI–CSA and PANI–CSA/PAA film. PANI–CSA/PI blend films had a good thermal stability of conductivity at high temperature. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:1863–1870, 1998     

Construction of a choline biosensor through enzyme immobilization on a poly(2‐hydroxyethyl methacrylate)‐grafted Teflon film

An amperometric choline biosensor was constructed by immobilizing choline oxidase (ChO) on poly(2‐hydroxyethyl methacrylate) (PHEMA)‐grafted Teflon (polytetrafluoroethylene, PTFE) film. Grafting was achieved by γ irradiation. PHEMA‐grafted Teflon films were activated with epichlorohydrin or glutaraldehyde to achieve covalent immobilization of enzyme onto the film. To decrease the diffusional barrier caused by the enzyme‐immobilized film, the film was stretched directly on the electrode. The PHEMA‐grafted Teflon film, therefore, had to have appropriate mechanical properties. Glucose oxidase (GOD) was used in the determination of optimum immobilization conditions, then these were applied to ChO. With GOD, the effect of activation type and film position in electrode on enzyme activity was studied and the highest catalytic activity was obtained when the enzyme was immobilized using glutaraldehyde and the film was stretched over the electrode surface. Further studies revealed that the films activated with glutaraldehyde, immobilized in 2 mg/mL ChO concentration, and stretched directly on the electrode were suitable (specific activity, 0.427 ± 0.068 U mg^?1) for use in the choline biosensor. The linear working range of this biosensor was found to be 52–348 μM, with a 40 ± 5 μM minimum detection limit. The response of the sensor, however, decreased linearly upon repeated use. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Thermal imidization of poly(amic acid) precursors on surface-modified poly(tetrafluoroethylene) films via graft copolymerization with glycidyl methacrylate

A novel method for preparing composites of polyimides (PI) laminated to poly(tetrafluoroethylene) (PTFE) films is reported. PI/PTFE composites were developed through thermal imidization of poly(amic acid) (PAA) precursors on surface-modified PTFE films. Surface modification of PTFE films was carried out via Ar plasma pretreatment of the films, followed by UV-induced graft copolymerization with glycidyl methacrylate (GMA). The surface composition and topography of the graft copolymerized PTFE films and the delaminated PI and PTFE surfaces were characterized by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM), respectively. The adhesion strengths of the PI (imidized PAA) on the GMA graft copolymerized PTFE films were evaluated as a function of various thermal imidization schedules. The adhesion reliability of the PI/PTFE composites was tested by a series of hydrothermal cycles. The development of strong Tpeel adhesion strengths of about 8 N/cm with excellent reliability for the PI/PTFE composites was attributable to the synergistic effect of coupling the curing of the epoxide functional groups of the grafted GMA chains with the imidization process of the PAA and the fact that the GMA chains were covalently tethered onto the PTFE surface. The PI/PTFE composites delaminated via cohesive failure inside the PTFE substrates. The delaminated PI film with a covalently adhered 'rough' PTFE surface layer exhibited a water contact angle as high as 140°.     

Synthesis and characterization of poly(aniline) and poly(o-anisidine) films in sulphamic acid solution and their anticorrosion properties

Poly(o-anisidine) (POA) and polyaniline (PANI) coatings were synthesized on platinum (Pt) surface and stainless steel (SS) in monomer containing 0.50 M sulphamic acid (SA) solution by means of cyclic voltammetry (CV) technique. Meanwhile, poly(o-anisidine) film was also deposited with a different scan rate on SS electrode. The behaviour of PANI and POA films obtained on stainless steel examined by CV was different from the one obtained for PANI and POA on Pt electrode. The corrosion performances of PANI and POA coatings in 3.5% NaCl solution were investigated with anodic polarization technique and electrochemical impedance spectroscopy (EIS). EIS measurements verified the effect of monomers and that of scan rate on corrosion inhibition of coatings on SS electrode. The results showed that POA film synthesized at low scan rate exhibited an effective anticorrosive property on SS electrode. POA synthesized at low scan rate and PANI coatings provided a remarkable anodic protection to SS substrate for longer exposure time than the one observed for POA coating produced at high scan rate as well as that of bare SS electrode.     

Thermal imidization of poly(amic acid) on Si(100) surface modified by plasma polymerization of glycidyl methacrylate

The plasma polymerization of glycidyl methacrylate (GMA) on pristine and Ar plasma-pretreated Si(100) surfaces was carried out. The epoxide functional groups of the plasma-polymerized GMA (pp-GMA) could be preserved, to a large extent, through the control of the glow discharge parameters, such as the radio-frequency (RF) power, carrier gas flow rate, system pressure, and monomer temperature. The pp-GMA film was used as an adhesion promotion layer for the Si substrate. The polyimide (PI)/pp-GMA-Si laminates, formed by thermal imidization of the poly(amic acid) (PAA) precursor poly(pyromellitic dianhydride-co-4,4′-oxydianiline) (PMDA-ODA) on the pp-GMA-deposited Si surface (the pp-GMA-Si surface), exhibited a 180°-peel adhesion strength as high as 9.0 N/cm. This value was much higher than the negligible adhesion strength for the PI/Si laminates obtained from thermal imidization of the PAA precursor on both the pristine and the argon plasma-pretreated Si(100) surfaces. The high adhesion strength of the PI/pp-GMA-Si laminates was attributed to the synergistic effect of coupling the curing of epoxide functional groups in the pp-GMA layer with the imidization process of the PAA, and the fact that the plasma-deposited GMA chains were covalently tethered onto the Si(100) surface. The chemical composition and structure of the deposited films were characterized, respectively, by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy, while the surface morphology of the deposited films was characterized by atomic force microscopy (AFM).     

PVP与PVA对原位聚合导电聚苯胺薄膜的影响

分别以水溶性高分子聚乙烯吡咯烷酮(PVP)和聚乙烯醇(PVA)为稳定剂,采用苯胺的分散聚合体系,在玻璃基片上原位沉积了表面光滑均匀、亚微米厚度的导电聚苯胺薄膜,改善了导电聚苯胺的加工性能。研究了薄膜的形貌、厚度及电导率。结果表明:聚苯胺薄膜表面光滑,黏附一些胶体粒子,以PVP为稳定剂制备的聚苯胺薄膜表观质量好于以PVA为稳定剂得到的聚苯胺薄膜,表面更加光洁致密;不同稳定剂影响聚苯胺薄膜厚度及性能,在其他实验条件相同的情况下,以PVA为稳定剂制备的聚苯胺薄膜厚度及电导率均高于以PVP为稳定剂制备的聚苯胺薄膜厚度和电导率。     

Synthesis of high-performance composites by in situ polycondensation and their mechanical properties

High-performance composites of vinylpyridine-styrene copolymers and polyamic acid (PAA) were prepared by the so-called ‘in situ polymerization method’. Poly(4-vinylpyridine-co-styrene) (P4VPy-St) and poly(2-vinyl pyridine-co-styrene) (P2VPy-St) were used as flexible matrix polymers. A molecular composite could be obtained from a polymer pair having an attractive interaction such as a coulombic interaction. Their morphologies were observed by scanning electron microscopy (SEM); mechanical properties of these composites were studied by tensile tests. The PAA content dependence of tensile strength for the composite films obtained by the in situ polymerization method was investigated. The tensile strength of the resulting composite was about 1.5 times higher than that of PAA film. The coulombic interaction between the pyridine moiety in the matrix copolymer and resulting PAA enhanced both the miscibility and mechanical properties of the composites. Furthermore, a polyimide (PI) structure was formed by stepwise heat-treatment and greatly enhanced the tensile strength of the composite films.     

Covalent immobilization of α‐amylase onto thermally crosslinked electrospun PVA/PAA nanofibrous hybrid membranes

Poly(vinyl alcohol)/poly(acrylic acid) (PVA/PAA) nanofibers with the fiber diameter of 100–150 nanometers were fabricated by electrospinning. PVA/PAA nanofibers were crosslinked by heat‐induced esterification and resulting nanofiber mats insoluble in water. α‐Amylase was covalently immobilized onto the PVA/PAA nanofiber surfaces via the activation of amine groups in the presence of 1,1′‐carbonyldiimidazole. The immobilized α‐amylase has more resistance to temperature inactivation than that of the free form and showed maximum activity at 50°C. pH‐dependent activities of the free and immobilized enzymes were also investigated, and it was found that the pH of maximum activity for the free enzyme was 6.5, while for the optimal pH of the immobilized enzyme was 6.0. Reuse studies demonstrated that the immobilized enzyme could reuse 15 times while retaining 81.7% of its activity. Free enzyme lost its activity completely within 15 days. Immobilized enzyme lost only 17.1% of its activity in 30 days. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effect of acids on in situ polyaniline film formation

The chemical oxidation of aniline with ammonium persulfate (APS) to form polyaniline (PANI) films has been studied in different aqueous acid media such as sulfuric, nitric, phosphoric and acetic acids. A comparison was made between the yields of PANI film deposition during the polymerization from these media with the corresponding one obtained previously from aqueous HCl solution. The degradation of the formed PANI films at the beginning of polymerization obtained at the higher concentrations of HCl is absent when the other acids under consideration were used. The effect of acid concentration on the yield and growth rate of the PANI film was studied. The variation in the yield and growth rate of the polymer films at different acid concentrations was explained on the basis of the electrostatic repulsion and the screening effects. Copyright © 2004 Society of Chemical Industry     

Fabrication of bioanode by using electrically conducting polythiophene via entrapment technique

A glassy carbon electrode (GCE) was tailored with conducting polymer polythiophene and further immobilized by an enzyme glucose oxidase (GOx). A thin film of polymer was developed by electrochemical polymerization of thiophene monomer. During electrochemical polymerization of the monomer the enzyme GOx and the redox active mediator ferritin (Frt) were entrapped within this polymer matrix. In this novel approach, the entrapment of enzyme and mediators within a polymer matrix occurs without chemical reaction that could affect their activity. The entrapment of enzyme and mediator within the conducting polymer matrices increases the surface area of the electrode. The tailored GCE/Ptp/Frt/GOx electrode showed a high catalytic activity. The increased surface area causes a high rate of electron transfer between the electrode and Frt engaged as an electron transfer mediator. The electrochemical properties of the electrode were determined by cyclic voltammetry (CV) and linear sweep voltammetry (LSV). The fabricated bioanode showed a current density of 3.9mA cm^?2 at 1.0 V vs. Ag/AgCl in a 45 mM glucose solution and suggests proficient chances in biofuel cells (BFCs) applications.     

Antioxidant capacity of robust polyaniline–ethyl cellulose films

Ethyl cellulose films containing up to 17% polyaniline (PANI EC film) were prepared from ethanolic solutions. The antioxidant capacity of the PANI EC films was examined using the oxygen radical absorbance capacity (ORAC) assay, and the films demonstrated very efficient peroxyl free radical scavenging activity. A good correlation was also obtained between the net ORAC curve area and the size of the tested film, indicating the homogenous dispersion of active PANI powder across the film. Reduced PANI presented greater peroxyl radical scavenging activity than more oxidized as-prepared forms. The influence of the PANI EC films on the oxidation of Ropufa oil was determined after incubation at 60 °C for several days. The oil stored in the presence of a PANI EC film was found to exhibit a lower peroxide value than in the absence of PANI, indicating that the conducting polymer can inhibit the oxidation of fish oil.