PPA Films Research Articles

A Flexible Strain Sensor with High Electrical Conductivity, Rapid Electrothermal Response, and High Strain Sensitivity for Real‐Time Monitoring of Human Joint Movement

AbstractHerein, a flexible film, called PPA film, is designed as a multifunctional sensor with high electrical conductivity, rapid electrothermal response, and high strain sensitivity. The film contains polyvinyl alcohol (PVA), graphene nanosheets (GNs), nanocellulose crystals (CNCs), polydopamine (PDA), and silver nanoparticles (Ag NPs), symbolized as PPA film. The CNCs enhance the dispersion of the GNs during film formation; the stacked GNs change heat conduction and resistance during film bending; PDA serves as a linking agent; Ag NPs improve the conductivity (i.e., 2.65 × 103 S/m) of the film during electrothermal response measurement. A flexible strain sensor designed from PPA films is mounted on the skin surface of human joints to monitor human movement in real time. The sensor exhibited good stability and cycling durability, i.e., the resistance variation remained stable during the bend‐release repetitions for 600 cycles at 1.2 % strain. The flexible sensors exhibited highly sensitive to bending strain, i.e., 30.5 of the gauge factor (GF), and can be applied to monitor bending motions of human joints, such as finger, wrist, elbow, and knee joints.In addition, the PPA films exhibit very high joule heat generation ability and demonstrate its applicability as a joint or stomach warmer and sensor. The as‐designed flexible sensor is a promising candidate for application in environmentally friendly and multifunctional wearable devices.

Programmable Polymer Actuators Perform Continuous Helical Motions Driven by Moisture.

Powerful soft actuators that can perform programmable actuations are highly desired for the development of soft robotics. Herein, we report a moisture-driven polymer actuator, PPA, which is a composite of poly(3,4-ethylenedioxythiophene)/polyvinyl alcohol/copolymer of acrylic acid and 2-acrylanmido-2-methylpropanesulfonic acid. PPA can not only generate powerful actuation with a contractile stress up to 13 MPa, but can also perform programmable helical motions. PPA films with internal stress along the radial directions were prepared by a simple solution-casting method. Driven by moisture, rectangular strips cut from the same PPA film but with different cutting angles (the oblique angle between the long axis of the PPA strip and the radial axis of the PPA film) can perform direct bending and left-handed or right-handed helical motions, demonstrating the generation of chirality from asymmetric internal stress. By modulating the distribution of internal stress in PPA strips, their moving direction and speed are readily prescribed. The powerful and programmable PPA strips can be used to make soft devices, such as moisture-responsive switches and transporters. Our strategy of generating and utilizing internal stress in responsive polymers represents a promising platform for fabricating smart soft actuators.

Synthesis and properties of novel poly(benzimidazopyrrolone amide)s containing pyridine moieties

AbstractA series of new poly(benzimidazopyrrolone amide) (PPA) copolymers were synthesized by a two‐step procedure, which was the solution polycondensation of a novel pyridine‐containing tetraamine with various aromatic dianhydrides at a room temperature and cyclization of the resulting prepolymers at a high temperature, respectively. The resulting prepolymers from the solution polycondensation, that is, poly(amide amino acid)s (PAAAs), had inherent viscosities of 0.82–0.91 dL/g; then, tough and flexible PPA films could be successfully prepared by the casting of the PAAA solutions onto a glass substrate followed by thermal curing with a program temperature procedure up to 350°C. The obtained PPA films exhibited not only excellent thermal properties with onset decomposition temperatures in the range 502–521°C, glass‐transition temperatures in the range 299–337°C, and residual weight retentions at 700°C in air of 29.1–34.8% but also good mechanical properties with tensile strengths of 102.1–115.9 MPa and elongations at break of 6.8–7.4%. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

The interaction of the polyphenylacetylene surface with biological environments studied by XPS, RAIRS and biological tests

A pi-conjugated polymer, polyphenylacetylene or PPA, has been tested for its possible applications as biosensor or biomaterial. Protein adsorption was investigated by incubating PPA films in solutions of bovine serum albumin (BSA) dissolved in phosphate buffer (PBS) having increasing protein concentration. Investigations on the PPA films were carried out by means of two surface analysis techniques, X-ray photoelectron spectroscopy (XPS) and reflection-absorption infrared spectroscopy (RAIRS). Desorption of BSA from the PPA surface was also investigated. Finally, the cytototoxicity of the PPA surface was checked by measuring viability and proliferation of lymphoma macrophages and SAOS osteoblasts grown in the presence of the polymer.

DNA Hybridization on Plasma-Polymerized Allylamine

Surface Plasmon Enhanced Fluorescence Spectroscopy (SPFS) has been used to monitor the hybridization reaction of fluorophore-labeled 15mer target oligonucleotides from solution to probe DNA previously immobilized on plasma-polymerized allylamine films (ppA). The surfaces were treated with 254 nm UV light to covalently link the probe DNA to the ppA films. Since strong unspecific adsorption would occur between target DNA and unreacted amino groups on the polymer surface, any remaining reactive moieties in the polymer film were neutralized by rinsing the substrate surface with succinic anhydride after probe adsorption and before target hybridization. The SPFS data were utilized to determine hybridization affinity constants (KA) for complementary targets (MM0) as well as mismatch 1 (MM1) and mismatch 2 (MM2) hybridization reactions. Complementary target (MM0) DNA hybridization was shown to have a significantly higher KA than that MM1 and MM2. The three-dimensional network of the ppA appears to allow a similar...

XPS and FT‐IR spectroscopy study of albumin adsorption on the surface of a π‐conjugated polymer film

AbstractThe interaction between thin films of polyphenylacetylene (PPA) and bovine serum albumin (BSA) dissolved in phosphate buffer solution (PBS) was studied by x‐ray photoelectron spectroscopy (XPS) and Fourier‐transform infrared spectroscopy (FT‐IR) performed in reflectance mode. PPA is a semiconducting π‐conjugated polymer consisting of a polyene backbone with phenyl pending groups, that has been used in the preparation of humidity sensors; therefore, we have tried to pre‐test PPA films for possible applications as biosensors.Thin films of PPA were incubated in buffered albumin solution (BSA/PBS) for increasing exposure times (24–96 hours). BSA adsorption on the PPA film surface takes place as demonstrated by the appearance of the N 1s signal and by the modifications in the C 1s core‐level signal in the XPS spectra of the samples treated with albumin solution; time‐dependent adsorption is also observed. Phosphate salts are co‐adsorbed on the PPA surface upon treatment with BSA/PBS solution. Albumin adsorption on the PPA surface was confirmed by FT‐IR measurements. Copyright © 2004 John Wiley & Sons, Ltd.

Effect of electrosynthesis conditions on the structure and optical properties of the polyphenylacetylene films

The method of electrochemical synthesis of conducting polyphenylacetylene (PPA) layers on Pt, Cu, SnO 2 , ITO-surfaces was developed. The influence of electrosynthesis conditions on the structure, morphology, optical spectra and conductivity of PPA films have been studied. The influence of electrosynthesis condition on the electron spectra of PPA films allow to propose the possibility of electrochemical generation in PPA films the free charge carriers by the mechanism of electrochemical doping.

Influence of Ar + ion irradiation on the properties of plasma polymerized acetylene films

Plasma polymerized acetylene is an amorphous material whose properties can be significantly changed upon ion irradiation. In this work, the modification of the structural, optical, electrical and mechanical properties of PPA films by 150-keV Ar + ions is investigated. The ion fluence varied from 10 18 to 10 21 m −2 at a constant current of 100 μA. Structural and optical properties were analyzed using infrared and ultraviolet-visible spectroscopies, respectively. From oxygen plasma etching experiments, further structural information was obtained. A two-point probe was employed to measure the electrical resistivity. Hardness measurements were made using a nanoindenter. The infrared spectra showed depletion of hydrogen and increased concentration of carbon double bonds with increasing ion fluence. As a consequence, the optical, electrical and mechanical properties were also modified. The optical transmission in the UV and visible regions were diminished with increasing ion fluence, reflecting a narrowing of the optical gap. The electrical resistivity decreased with increasing fluence; a decrease of 11 orders of magnitude with respect to the pristine film was measured for the highest fluence (10 21 m −2). A strong increase of hardness was observed as the ion fluence was increased. A hardness of 10.6 GPa was measured after irradiation at the fluence of 10 21 m −2. The oxygen-etching rate decreased significantly as the fluence was increased. Both the hardness and etching results strongly indicate that a highly cross-linked structure was formed at high ion fluences.

Simultaneous polymerization and formation of polyphenylacetylene film by Nd(P204)3–Fe (AA)3–Al(i‐Bu)3 combined catalyst system

AbstractThe simultaneous polymerization and formation of polyphenylacetylene film by Nd(P204)3–Fe(AA)3–Al(i‐Bu)3 catalyst system have been investigated. The combined catalytic effects between rare earth phosphonates with MT(naph)x or Fe(AA)3 systems are first proposed and compared. The polymerization features and kinetic behaviors with Nd(P204)3–Fe(AA)3‐Al(i‐Bu)3 system are described and discussed. The combined catalytic effects have the following order, respectively: Fe ≫ Co > Cr > Mn‐Ni, Nd(P204)3‐Nd(P507)3 > Nd(P350)3 and Tb > Sm > Yb > Ho > Lu > Dy > Nd‐Er‐Pr > Y‐Tm > Ce > Gd > La. The overall polymerization activation energy was found to be 20.8 kJ/mol showing coordination‐anionic polymerization characteristic. PPA films so obtained are very similar to the rare earth ones. © 1995 John Wiley & Sons, Inc.

Morphological study of poly(phenylacetylene) films, prepared with Rh(I) catalysts, from scanning microscopy investigations

The morphological evolution of as-grown poly(phenylacetylene) (PPA) free standing films has been studied. Investigations performed by scanning electron microscopy show that the freshly prepared PPA films exhibit a glass-like morphology which subsequently evolves into a microsphere structure. After ageing for 3 months at room temperature, PPA films reach a stable enamel-like phase. The chemical structure of the Rh(I) catalysts does not appear to influence the morphology of PPA. However, different catalysts yield different rates of morphological evolution.

Iodine incorporation into polymeric films investigated by angle-resolved XPS

Distribution of elements into subsurface layers (up to 120 Å thickness) of polyphenylacetylene (PPA) films doped with I 2 vapour has been determined by X-ray photoelectron spectroscopy data using a unique numerical technique. Concentration of incorporated iodine has been shown to increase with exposure time; the concentration profiles are dome-shaped and iodine does not penetrate much into the bulk of PPA films, even when exposed to I 2 vapours for 1 h. The depth of the layer corresponding to maximum iodine concentration is directly proportional to the iodine exposure time. The non-homogeneous distribution of the doping species in the polymer may be responsible for the low conductivity observed for heterogeneously doped PPAfilms.

High photosensitivity in cis‐polyphenylacetylene films irradiated with 60Co γ‐ray

AbstractThis paper reports that 60Co γ‐ray irradiation can convert cis‐polyphenylacetylene (cis‐PPA) films prepared with rare‐earth coordination catalysts to highly photosensitive materials. The dependence of the photosensitivity on irradiation dose, preparation methods, and microstructure of the PPA films has been investigated by means of a potential discharge technique. The photosensitivity was enhanced with increasing irradiation dose. The critical dose to produce a light response was 5 × 103 Gy. The maximum surface potential discharge rate was 618 V/s, and the dark decay was approximately 2 V/s for cis‐PPA films irradiated with 60Co γ‐ray (dose: 2 × 105 Gy). The cis‐transoidal‐PPA and an electrophotographic photoreceptor device incorporating cis‐PPA showed a higher irradiation effect. The structure and properties of 60Co γ‐ray irradiated rare‐earth PPA films are similar to the unirradiated films.

Electrochemical Properties of Electropolymerized Poly(1-pyrenamine) Films

Abstract The electropolymerization of 1-pyrenamine (PA) in an acetonitrile solution led to the polymeric film formation on electrode surfaces. The chemical, spectroscopic, electrical and electrochemical characterization of the resulting poly(1-pyrenamine) (PPA) films was carried out. The number-average molecular weight of the PPA film, measured by gel permeation chromatography, was 1.8×103, corresponding to the degree of the polymerization of ca. 8. The PPA films were polymer-anion composites which contained ca. 0.3 anions (e.g., BF4−) per repeating aromatic unit, which is considered to be composed of three PA molecules. The oxidized form of the PPA film displayed the ESR response. The g factor was 2.0082 and the concentration of radical in the PPA film was determined to be 4.8×1019 e−g−1. The conductivities of the PPA films in the dry state at 300 K were in the range 10−11–10−10 S cm−1. The PPA film was electroactive in an aqueous solution as well as in a non-aqueous solution. The cyclic voltammetric responses depended on pH of aqueous solutions and supporting electrolyte in non-aqueous solutions. The thickness(φ) of the PPA film and the surface concentration(Γ) of the electroactive site in the PPA film were proportional to the amount (Q) of the charge passed during the electrolysis (when Q<ca. 120 mC cm−2). The volume concentrations of the electroactive site were 9.7×10−4 and 1.7×10−3 mol cm−3 for the PPA films prepared in the NaClO4 and TBABF4 (tetrabutylammonium tetrafluoroborate) electrolytes, respectively. From the normal pulse voltammetric, potential-step chronoamperometric and potential-step chronocoulometric experiments of the PPA films in a 0.2 M NaClO4 aqueous solution (pH 1.0), the effective apparent diffusion coefficient (Dapp) for the diffusion-like charge transport within the PPA films, and the standard rate constant (k°) and anodic transfer coefficient (αa) of the heterogeneous electron-transfer reaction between the In2O3 electrode and the electroactive site in the PPA film were estimated to be (1.5±0.5)×10−10 cm2 s−1, (1.9±0.4)×10−5 cm s−1 and 0.67±0.03, respectively.