Study of the actions of BTEX compounds on polypyrrole film as a gas sensor

Polypyrrole (PPy) thin films were prepared electrochemically at a constant potential. Gas-sensing behaviors, including reproducibility, sensitivity, and response time to various benzene, toluene, ethylbenzene, and xylene (BTEX) compound concentrations, were investigated. BTEX compounds were found to be able to compensate for the doping level of PPy and, hence, decrease the conductivity of PPy on exposure to them. A reasonable reproducibility of the resistance change (ΔR) was obtained. The sensitivity for each compound was 2.3 mω/ppm (benzene), 0.4 mω/ppm (toluene), 8.3 mω/ppm (ethylbenzene), and 2.9 mω/ppm (xylene). An adsorption model correlated well with the experimental results and was used to interpret the sensing behaviors. The parameters of this model, including the adsorption equilibrium constant and the ΔR caused by a pseudomonolayer of the detecting layer {[m(r₁ − r₀)]/n, where m is the number of active sites on the pseudomonolayer; r₁ and r₀ are the site resistances when the site is vacant and occupied, respectively; and n is the thickness of the film}, were determined. According to the parameters, toluene vapor had the most prominent effect in undoping PPy film but the poorest affinity to the active sites of the film. On the other hand, ethylbenzene showed the highest affinity to PPy film compared to the other BTEX compounds and consequently led to the highest sensitivity for such a sensor. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 954–961, 2001     

Properties of polyamide 6,10/poly(vinyl alcohol) blends and impact on oxygen barrier performance

The oxygen transmission rate, average volume of free‐volume cavities (V_f) and fractional free volume (F_v) of polyamide 6,10 (PA610)/poly(vinyl alcohol) (PVA) (i.e. PA610_xPVA⁰⁵_y, PA610_xPVA⁰⁸_y and PA610_xPVA¹⁴_y) blend films reduced to minimum values when their PVA contents reached corresponding optimal values. Oxygen transmission rate, V_f and F_v values obtained for optimal PA610_xPVA^z_y blown films were reduced considerably with decreasing PVA degrees of polymerization. The oxygen transmission rate of the optimal bio‐based PA610₈₀PVA⁰⁵₂₀ blown film was only 2.4 cm³ (m²·day·atm)^?1, which is about the same as that of the most often used high‐barrier polymer, ethylene–vinyl alcohol copolymer. Experimental findings from dynamic mechanical analysis, differential scanning calorimetry, wide‐angle X‐ray diffraction and Fourier transform infrared spectroscopy of the PA610_xPVA^z_y blends indicate that PA610 and PVA in the blends are miscible to some extent at the molecular level when the PVA contents are less than or equal to the corresponding optimal values. The considerably enhanced oxygen barrier properties of the PA610_xPVA^z_y blend films with optimized compositions are attributed to the significantly reduced local free‐volume characteristics. © 2017 Society of Chemical Industry     

A Model of Mechanotransduction in Polyvinyl Alcohol-Based Composite Hydrogels for Regulating Musculoskeletal Differentiation

In regenerative medicine, extracellular matrix (ECM)-inspired materials are currently being explored to imitate mechanotransduction pathways and control cell fate. In musculoskeletal tissue regeneration, enhancing mechano-biological signals require biomaterials that are both biocompatible and viscoelastic and can retain water content. Herein, based on these requirements, various polyvinyl alcohol (PVA)-based composite hydrogels, reinforced by polyhydroxy butyrate (PHB) nanofibers, are proposed to differentiate equine adipose-derived stem cells for musculoskeletal regeneration. To study the role of fiber embedding in improving scaffold properties, different nanofiber assemblies, including chopped short ones with random orientation (PVA_S), single-layer (PVA_L1), and double-layer membranes (PVA_L2) are positioned into the PVA matrix. PHB reinforcements negatively affect swelling and positively enhanced phase transition temperatures and crystallinity of PVA hydrogel. According to mechanical analysis results, compositing with PHB nanofibrous layers strengthen the PVA matrix due to some restrictions on PVA chain mobility. Gene expression investigations also reveal that higher matrix stiffness after layering with two PHB membranes (PVA_L2) promotes osteogenesis, while the random addition of short-chapped fibers (PVA_S) facilitate tenogenic differentiation. As a consequence of the findings, fiber placement is crucial to the mechanical properties of composite hydrogels that ultimately control musculoskeletal differentiation signals through mechanosensing pathways.     

Oxygen barrier,free volume,and blending properties of fully bio-based polyamide 11/poly(vinyl alcohol) blends

Fully bio-based polyamide 11 (PA11) was melt-blended with poly(vinyl alcohol) (PVA) with varying degrees of polymerization (DP) to prepare PA11_xPVA^z_y. The PA11_xPVA^z_y films demonstrated the lowest oxygen transmission rates (OTR) and free volume characteristics, when PVA contents of each PA11_xPVA^z_y series reached a corresponding critical concentration. The minimum OTR and free volume characteristics obtained for the optimal PA11_xPVA^z_y films reduced significantly with decreasing PVA DPs. The OTR of the optimal PA11_xPVA^z_y blown film was 1.07 cm³ m⁻² day⁻¹ atm⁻¹, which is near to that of the ethylene-vinyl alcohol copolymer high-barrier polymer. The results of dynamical, mechanical, and other experimental characterizations demonstrated that PA11 and PVA are compatible to some extent when PVA concentrations are less-than or equal to the respective critical values. The enhanced oxygen permeation resistance and free volume characteristics for optimal PA11_xPVA^z_y films are at least partly ascribed to the improved hydrogen-bonded molecular interactions between PA11 CO groups and PVA O─H groups. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48562.     

Fourier transform infrared study of polypyrrole–poly(vinyl alcohol) conducting polymer composite films: Evidence of film formation and characterization

The electrochemical preparation of polypyrrole (PPY)–poly(vinyl alcohol) (PVA) conducting polymer composite films on an indium–tin oxide glass electrode from an aqueous solution containing a pyrrole monomer, a p‐toluene sulfonate electrolyte, and a PVA insulating polymer is reported. The prepared PPY–PVA composite films were characterized by Fourier Transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), and conductivity measurements. The FTIR study showed that the composite of PPY and PVA formed through bond formation between PVA and the p‐toluene sulfonate dopant anion. The conductivity data of PPY–PVA showed that with increasing PVA concentration in the pyrrole solution, the conductivity of the prepared PPY–PVA film increased up to a certain level due to an increase in conjugation length, and later, it decreased with further increases in the PVA concentration in the solution due to a decrease in conjugation length. This was supported by the FTIR band intensity I₁₅₆₀/I₁₄₈₀. The TGA results show that the PPY–PVA polymer composite film was thermally more stable than the PPY film. A shielding effectiveness of 45.6 dB was exhibited by the PPY–PVA composite film in the microwave frequency range. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4107–4113, 2006     

A transdermal diltiazem hydrochloride delivery device using multi-walled carbon nanotube/poly(vinyl alcohol) composites

Membranes with high strength and elasticity are of great demand in patch therapy. Similar membranes have been developed by combining carboxy-functionalized multiwalled carbon nanotube (c-MWCNT) with different poly(vinyl alcohol) (PVA) as potential diltiazem delivery device through aqueous mixing. High molecular weight PVA (PVA_H) produced stronger interaction with c-MWCNT than low molecular weight PVA (PVA_L) preferably at low concentration. Positive changes in favor of PVA_H in infrared and solid state ¹³C nuclear magnetic resonance spectroscopy, wide angle X-ray scattering, thermal stability, morphology and dry and wet mechanical properties clearly demonstrate that. Fibrillar c-MWCNT array at 1 wt.% in PVA_H (PVA_H/1) has drastically improved PVA crystalline cell dimension, tensile strength (201%) and elongation (196%) than neat PVA_H whereas the similar improvement is much less (100% and 185%) in PVA_L (PVA_L/1) due to globular morphology. Instead, c-MWCNT performed better at 0.5 wt.% in PVA_L (PVA_L/0.5). The kinetic data reflects better encapsulation and slower release by PVA_H (5.87%) than PVA_L (10.17%) due to greater interfacial interaction.     

Synthesis of a new type poly(vinyl alcohol)/peat/bamboo charcoal/KNO3 composite bead used as biofilter material

A new type poly(vinyl alcohol) (PVA)/peat/bamboo charcoal (BC)/KNO₃ composite bead was prepared, which has a diameter of 2.4–6.0 mm and a density of 1.133 g/cm³ and is a porous spherical particle. The biochemical kinetic behaviors of n‐butyl acetate in PVA/peat/BC/KNO₃ spherical composite bead biofilter (BC biofilter) and PVA/peat/granular activated carbon (GAC)/KNO₃ spherical composite bead biofilter (GAC biofilter) were investigated. The values of half‐saturation constant K_s for BC biofilter and GAC biofilter were 27.89 and 27.95 ppm, respectively. The values of maximum reaction rate V_m for BC biofilter and GAC biofilter were 13.49 and 13.65 ppm/s, respectively. Zero‐order kinetic with the diffusion limitation was regarded as the most adequate biochemical reaction model for the two biofilters. The microbial growth rate and biochemical reaction rate for two biofilters were inhibited at higher inlet concentration, and the degree of inhibitive effect was more pronounced in the inlet concentration range of 100–800 ppm. The biochemical kinetic behaviors of the two biofilters were similar. The maximum elimination capacity of BC biofilter and GAC biofilter were 111.65 and 122.67 g C/h m³ bed volume, respectively. The PVA/peat/BC/KNO₃ composite bead was suitable as a biofilter material. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effects of Plasticizing on Mechanical and Viscous Characteristics of Poly(vinyl alcohol): A Comparative Study between Glycerol and Diethanolamine

Although plasticizing materials by modification with small-molecular chemicals has been extensively utilized in the industrial community, processing poly(vinyl alcohol) (PVA) at high concentrations (C_PVA) or with a high degree of polymerization (DP) remains challenging. Optimization the plasticizing conditions is one means of addressing this issue. In this study, two types of frequently used plasticizers, glycerol (GLY) and diethanolamine (DEA), are chosen to plasticize PVA resin with a DP of 2400. Both PVA/plasticizer films possess excellent optical transmittance and mechanical ductility, whereas the films blended with DEA exhibit higher strength than the PVA/GLY films. The viscosity variation in the temperature (T_op)–C_PVA space is monitored by real-time viscous flow testing, demonstrating that DEA is more effective for reducing the viscosity of PVA, which should improve the processability, facilitating film-forming from concentrated solutions. Furthermore, density functional theory calculations and molecular dynamics simulations illustrate that the PVA/DEA system has a lower binding energy, longer hydrogen bond length, and higher isotropic diffusion coefficient, indicating a stable hydrogen bond network and homogenous dispersion of the plasticizer, leading to good solution fluidity and mechanical performance. This study is significant for guiding the design and manufacture of optically transparent, high-performance PVA films as polarizer precursor.     

Preparation of the flexible polypyrrole/polypropylene composite fibrous film for electrochemical capacitor

Polypyrrole (PPy)/polypropylene fibrous membrane (PPF) composite materials with different PPy contents are prepared through in situ chemical oxidation polymerization in the pyrrole atmosphere at room temperature by dissolving the FeCl₃·6H₂O in methanol and acetonitrile as oxidant. The morphology of the composite is examined by scanning electron microscope (SEM), the conductivities of the composites are measured by convenient four‐probe method, and the properties of the capacitor cells assembled by the obtained PPy/PPF are investigated by cyclic voltammetry (CV), galvanostatic charge/discharge, and electrochemical impedance spectroscopy (EIS) measurements. The results show that the morphology, conductivity, and the capacitor property of the composite are influenced strongly by the solvent of the oxidant. The capacitor assembled by the PPy/PPF prepared by using acetonitrile as the solvent for FeCl₃^.6H₂O can adapt for quick charge/discharge, and exhibit the highest capacitance of about 72.5 F g^?1 when the PPy content is about 8.0%. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Transport properties in polypyrrole powders and in PPy–PVA composites: Evidence for bipolaronic clusters

Experimental results on electrical conductivity of both doped polypyrrole (PPy) powder and conducting poly(vinyl alcohol) (PVA)–PPy composite are presented. In each case, FeCl₃ has been used as the oxidizing–polymerizing agent. Results are interpreted on the basis of a model in which counter-ions act through their attractive potential by forming conducting ways between chains and allowing transverse conduction. In the case of PPy powder, the major contribution to conduction mechanisms is hopping between polaronic clusters. In the case of the composite, an additional contribution results from fluctuation-induced tunneling through thin insulating PVA barriers. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68:709–713, 1998     

Enhanced electrosorption capacity for lead ion removal with polypyrrole and air‐plasma activated carbon nanotube composite electrode

Polypyrrole (PPy) and air‐plasma activated carbon nanotube (CNT) composites (P‐CNT‐PPy) prepared via in situ chemical oxidative polymerization are studied to improve the electrosorption capacity of CNT‐based electrodes for the removal of lead ions. For comparison, the PPy prepared on the CNTs without plasma activation is labeled as CNT/PPy. The morphology of the composite was observed by scanning electron microscopy (SEM), and pore structures were studied by N₂ adsorption‐desorption isotherms. The electrochemical capacitance properties of the composite were measured by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic charge‐discharge in lead solutions. With plasma‐activation, the specific surface area of the P‐CNT‐PPy composite is larger than that of CNT/PPy. Additionally, the P‐CNT‐PPy composites exhibit excellent electrochemical performance in lead solution, with a higher specific capacitance and smaller charge transfer resistance than that of CNT/PPy. XPS elemental analysis and electrosorption and regeneration results show that the electrosorption and desorption process is reversible under a voltage of 450 mV. The electrosorption kinetics of P‐CNT‐PPy electrodes abide by pseudo‐second‐order model reaction. The lead ion electrosorption experiments agree with the Langmuir model, and the equilibrium electrosorption capacity of the P‐CNT‐PPy electrodes is 3.6 and 1.3 times higher than that of the CNT and CNT/PPy, respectively. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41793.     

Mechanical properties of films of poly(vinyl alcohol) derived from vinyl trifluoroacetate

In order to study the influence of the stereoreguralities of polymer chains on the mechanical properties of films of poly(vinyl alcohol) (PVA)_(VTFA) derived from vinyl trifluoroacetate, the strength of the film was measured. In the case of undrawn PVA_(VTFA) films, Young's modulus and strength at break were the smallest at the annealing temperature of about 100°C. It is considered to be due to the melt of small microcrystals and the increase in mobility of chains in amorphous parts. Young's moduli of undrawn PVA_(VTFA) films were in the range of 1.50–3.75 GPs and the values were higher than that (0.17–0.36 GPa) of undrawn film of commercial PVA with the low concentration of syndiotacticity and the high concentration of head-to-head bounds. In the case of drawn, annealed PVA_(VTFA) films, the maximum Young's modulus was about 20 GPa.     

Properties of polyamide 612/poly(vinyl alcohol) blends and their impact on free volume and oxygen barrier properties

Oxygen transmission rates and free volume properties (i.e. average volumes of free-volume-cavities (V_f), mean number of the free volume cavities per unit volume (I₃) and fractional free volume (F_v)) values of bio-based polyamide 612 (PA612)/poly(vinyl alcohol) (PVA) (i.e. PA612_xPVA⁰³_y, PA612_xPVA⁰⁵_y, PA612_xPVA⁰⁸_y and PA612_xPVA¹⁴_y) blend films were reduced to a minimum value, when their PVA content reached corresponding optimal values of 25, 20, 15 and 10 wt%, respectively. The minimum oxygen transmission rate, V_f, I₃ and F_v value obtained for the best PA612₉₀PVA¹⁴₁₀, PA612₈₅PVA⁰⁸₁₅, PA612₈₀PVA⁰⁵₂₀ and PA612₇₅PVA⁰³₂₅ bio-based blown films reduced considerably with decreasing PVA degrees of polymerization. As evidenced by the results of dynamical mechanical analysis, differential scanning calorimetry, wide angle X-ray diffraction and Fourier transform infrared spectroscopic experiments, PA612 and PVA are miscible to some extent at the molecular level when their PVA contents are ≤ the corresponding optimal values. The significantly improved oxygen barrier and free volume properties for the PA612_xPVA^z_y blend films with optimized compositions is at least in part to the enhanced intermolecular interactions between PA612 carbonyl groups and PVA hydroxyl groups.     

Synthesis of polypyrrole‐modified TiO2 composite adsorbent and its adsorption performance on acid Red G

The adsorption–desorption characteristics of Acid Red G (ARG) on the polypyrrole‐modified TiO₂ (PPy/TiO₂) composite as a novel adsorbent was investigated. PPy/TiO₂ was synthesized via the in‐situ polymerization of pyrrole monomer in the prepared TiO₂ sol solution. Results from X‐ray diffraction and Fourier transform infrared spectra indicated the formation of the PPy/TiO₂ composite. The adsorption experiments showed that the modification of PPy substantially improved the adsorption and regeneration abilities of PPy/TiO₂. The adsorption equilibrium was achieved in a short time of 20 min, and the adsorption kinetics followed the pseudo‐second‐order model. The Langmuir adsorption isotherm was found for PPy/TiO₂, with the maximum adsorption capacity of 179.21 mg/g. The regeneration experiments showed that PPy/TiO₂ could be successfully regenerated by simple alkali‐acid treatment. The adsorption efficiency of the regenerated PPy/TiO₂ adsorbent for ARG was still greater than 90% after regeneration for 10 times. Additionally, the adsorption efficiency of PPy/TiO₂ for the ARG effluent was still higher than 78% after adsorption–desorption for four times. It is expected that the PPy/TiO₂ composite can be considered as a stable adsorbent for the removal of dye. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Fabrication of Tiron‐doped polypyrrole/MWCNT composite electrodes with high mass loading and enhanced performance for supercapacitors

In this study, the aromatic sulfonate compound Tiron with high charge to mass ratio is used as an anionic dopant for synthesis of polypyrrole (PPy). The fabricated PPy is investigated for electrochemical supercapacitor (ES) application. Testing results show that Tiron allows reduced PPy agglomeration, smaller particle size and improved charge storage properties of PPy. High capacitance and improved capacitive retention at high scan rates are achieved by the fabrication of PPy/multiwalled carbon nanotube (MWCNT) composite electrode using safranin (SAF) as a co‐dispersant. The Tiron‐doped PPy electrode shows the highest capacitance of 7.8 F cm^?2 with a mass of 27 mg cm^?2. The Tiron‐doped PPy/MWCNT composite electrode shows good capacitance retention with a capacitance of 1.0 F cm^?2 at the scan rate of 100 mV s^?1. Symmetric supercapacitor cells are fabricated using PPy based active materials. An energy density of 0.36 mWh cm^?2 is achieved. The energy/power density and capacitance retention of the Tiron‐doped PPy/MWCNT ES is significantly improved in comparison with PPy‐based ES, prepared without Tiron or MWCNT. The Tiron‐doped PPy/MWCNT symmetric supercapacitor presents good cycling performance with 91.4% capacitance retention after 1000 charge–discharge cycles. The PPy/MWCNT composites, prepared using Tiron and SAF co‐dispersant, are promising electrodes for ES. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42376.     

Aligned three-dimensional microstructures of conducting polymer composites

The composites of polypyrrole (PPy) and poly(vinyl alcohol) (PVA) with aligned 3-dimensional (3D) microstructures have been fabricated via vapor deposition polymerization (VDP) of pyrrole onto the microstructured composites of PVA and FeCl₃ (PVA-FeCl₃) formed by directional freezing. In these composites, the microstructures of PVA act as the frameworks and the conducting polymer components provide the materials with conductive function. The composites are foam-like with low weight density. However, they have good mechanical properties, and can be easily mechanically processed into various desired shapes. The apparent conductivity of the composite containing 20 wt% PPy was measured to be approximately 0.1 S cm⁻¹. The ammonia gas sensor based on this 3D composite exhibited high sensitivity. The strategy developed here can be extended to fabricate the 3D microstructured conductive composites by using other conducting polymers or water-soluble polymers.     

State of water in chitosan–PVA hydrogel

The bound water fraction (X_BW) of a newly‐ developed pH‐sensitive, biodegradable chitosan‐polyvinyl alcohol (PVA) hydrogel crosslinked with glutaraldehyde (GA) was investigated as a function of the chitosan/PVA molar ratio, GA concentration (C_GA), and ionization state. Differential scanning calorimetry (DSC) was used to determine the X_BW of the initial hydrogel, and of the hydrogel equilibrated in pH 3 and pH 7 buffers. Changes in X_BW during swelling and shrinking of hydrogel were also investigated. In the initial state of hydrogel, X_BW increased with increasing PVA concentration (C_PVA), without being significantly affected by C_GA. In the buffer‐equilibrated hydrogels, X_BW decreased with increasing C_PVA and decreasing C_GA. The amount of bound water based on dry mass (C_BW) was substantially higher when the hydrogel was in the ionized (swollen) state compared to its unionized counterpart. This may be due to the association of a large quantity of water molecules with ? NH₃⁺ groups of chitosan when the gel swelled in the acidic environment. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3227–3232, 2006     

Enhanced dielectric and ferroelectric properties induced by Ag @ Pb(Zr,Ti)O3 in poly(vinyl alcohol) matrix composites: A solution casting approach

The present research work focused on the dielectric and electrical properties of silver (Ag) doped Pb(Zr,Ti)O₃ (PZT) particles embedded in a matrix of poly(vinyl alcohol) (PVA) via solution casting technique. The structural analysis confirmed the presence of Ag particles and the microstructural study revealed that both Ag and PZT particles were successfully homogenized over the polymer matrix. The Ag–PZT–PVA composites showed enhanced dielectric properties over a wide range of frequency and the dielectric constant value of such composites was significantly increased to 366 (100 Hz) at 1.1 wt % filler loading. The percolation threshold of the Ag–PZT–PVA composites was found to be 0.9 wt %. The experimental result well fitted to the percolation theory. The enhancement of dielectric constant of the resulting composite systems might be attributed to the increment of conductivity of the interlayer between PZT and PVA due to the presence of Ag particles, which improved the space charge polarization and Maxwell–Wagner–Sillars (MWS) polarization effects. Furthermore, the remnant polarization of the unpoled Ag–PZT–PVA composites (2P_r ～1.48 µC/cm² for 1.1.wt % of Ag–PZT) has also improved, which is favorable for enhanced ferroelectric properties of the composites. The present findings of the composites might be exploited in the potential application of high performance energy storage devices. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45583.     

Preparation of PANI–PVA composite film with good conductivity and strong mechanical property

The polyaniline (PANI)–polyvinyl alcohol (PVA) conductive composite films [doped with hydrochloride (HCl), dodecylbenzene sulphonic acid and amino sulphonic acid (NH₂SO₃H) aqueous solution] were synthesised by ‘in situ’ polymerisation, and their conductivities were compared. Among these composite films, HCl–PANI–PVA composite film possessed the highest conductivity that reached 1360?S·m^??1 [w_(PVA)?=?40%]. Meanwhile, the effects of PVA content, HCl concentration, oxidant ammonium persulphate (APS) dosage, reaction time and film drying temperature on tensile strength of the HCl–PANI–PVA composite films were studied. The tensile strength of the film was improved greatly due to effective mixture of PANI and PVA. When the PVA content was 40%, C_(HCl)?=?1.0?mol·L^??1, reaction time was 4.0?h, n_(APS)/n_(aniline)?=?1.0 and film drying temperature was 80°C, and the tensile strength of the HCl–PANI–PVA composite film reached the maximum of 60.8?MPa. At the same time, the structure of composite materials was characterised and analysed through ultraviolet spectrum and SEM.     

Examining the use of TiO2 to enhance the NH3 sensitivity of polypyrrole films

Polypyrrole/Titanium dioxide (PPy/TiO₂) composite thin films were prepared by polymerizing the monomer pyrrole in aqueous solution containing a certain amount of TiO₂ particles at room temperature, and their response to ammonia (NH₃) gas was examined systematically. Compared with the pristine PPy film, which reached the saturation at the concentration of NH₃ beyond 200 ppm, the composite films showed more stable response and higher sensitivity. Furthermore, the PPy/TiO₂ composite thin films exhibited a low detection limit of 2 ppm. The film thickness, which had a strong influence on the film sensitivity to NH₃, could be controlled by varying the polymerization time. The sensitivity to NH₃ gas of the samples with different content of TiO₂ and different molar ratio of PPy/TiO₂/oxidant was studied. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010