Effect Of Polymer Thickness Research Articles

Ultrathin Functional Polymer Modified Graphene for Enhanced Enzymatic Electrochemical Sensing.

Grafting thin polymer layers on graphene enables coupling target biomolecules to graphene surfaces, especially through amide and aldehyde linkages with carboxylic acid and primary amine derivatives, respectively. However, functionalizing monolayer graphene with thin polymer layers without affecting their exceptional electrical properties remains challenging. Herein, we demonstrate the controlled modification of chemical vapor deposition (CVD) grown single layer graphene with ultrathin polymer 1,5-diaminonaphthalene (DAN) layers using the electropolymerization technique. It is observed that the controlled electropolymerization of DAN monomer offers continuous polymer layers with thickness ranging between 5–25 nm. The surface characteristics of pure and polymer modified graphene was examined. As anticipated, the number of surface amine groups increases with increases in the layer thickness. The effects of polymer thickness on the electron transfer rates were studied in detail and a simple route for the estimation of surface coverage of amine groups was demonstrated using the electrochemical analysis. The implications of grafting ultrathin polymer layers on graphene towards horseradish peroxidase (HRP) enzyme immobilization and enzymatic electrochemical sensing of H2O2 were discussed elaborately.

Polypyrrole actuators: the effects of polymer thickness and voltage scan rate on fractional charging and isotonic actuation strain

For conducting polymer actuators to be practically useful, they need to be able to generate large forces and displacements and respond quickly. The simplest way to generate larger forces is to produce thicker actuators, but this approach has a negative impact on the response time. The effects of polypyrrole film thickness and voltage scan rate on the electrochemical actuation strain rate are investigated in this study. The rate of oxidative charging is shown to follow a standard Fickian diffusion model suggesting that the migration of ions into the polymer from the electrolyte is the dominant rate-determining mechanism. The migration rate is slow with full oxidation requiring several minutes for film thicknesses of just 10 μm. The free strains generated were found to be directly proportional to the oxidative charge passed. The isotonic actuation strains were additionally reduced by increasing applied stress and this effect was attributed to the increase in Young’s modulus that occurs during polypyrrole oxidation. A simple model is presented that predicts the change in modulus during oxidation and gives reasonable estimates of the isotonic actuation for PPy actuators of different thickness and when subjected to different stresses.

Novel amperometric xanthine biosensor based on xanthine oxidase immobilized on electrochemically polymerized 10-[4H-dithieno(3,2-b:2′,3′-d)pyrrole-4-yl]decane-1-amine film

In this paper, a novel amperometric xanthine (X) biosensor is constructed by xanthine oxidase (XOx) immobilization on the pencil graphite electrode (PGE). Xanthine oxidase is immobilized using glutaraldehyde (GA) on the electrochemically polymerized conducting polymer film. The detection of xanthine is based on its consumed amount due to the enzymatic reaction of xanthine oxidase. The effects of polymer thickness, applied potential, pH, and temperature were investigated and optimum parameters were found to be five cycles, +5V, +0.5V and 30°C, respectively. Storage stability, operation stability of the enzyme electrode, and effect of interferant substances on the amperometric response were also studied. In order to verify the applicability of proposed biosensor, fabricated electrode was used to measure the xanthine concentration in chicken meat samples. The present xanthine biosensor with high selectivity, sensitivity, and stability is promising for practical applications.

Application of the Surface Resistance Technique to Study the Metal|Polymer Interface: A Review Article

The use of surface resistance changes as an alternative method to study the metal|polymer interface is reviewed considering both experimental and theoretical aspects. The experimental arrangement in these investigations is, in general, one in which a polymer film is supported on a thin gold film, whose thickness is of the order of the mean free path of the conduction electrons (gold film thickness, φm ∼30 nm). Particular emphasis is laid on the effects of polymer thickness, electrolyte composition, degree of oxidation, and deactivation and reactivation processes of the polymer film on the metal film conductance. Relevant experiments, where the technique was employed to study the redox site distributions at the metal|polymer interface, during oxidation, deactivation and degradation of the polymer, were specially considered. The simple scattering model to explain surface resistance changes of a thin metal film coated with a poly(o-aminophenol) film is outlined on the basis of the specularity parameter, which represents the probability of an electron being reflected specularly or diffusely at the metal film surface. Information obtained by means of surface resistance is compared with that obtained by employing more traditional techniques such as cyclic voltammetry and rotating disc electrode voltammetry. Keywords: Degree of oxidation, Metal-polymer interface, Poly(o-aminophenol) films, Scattering model, Surface Resistance

Application of the Surface Resistance Technique to Study the Metal|Polymer Interface: A Review Article

The use of surface resistance changes as an alternative method to study the metal|polymer interface is reviewed considering both experimental and theoretical aspects. The experimental arrangement in these investigations is, in general, one in which a polymer film is supported on a thin gold film, whose thickness is of the order of the mean free path of the conduction electrons (gold film thickness, φm ∼30 nm). Particular emphasis is laid on the effects of polymer thickness, electrolyte composition, degree of oxidation, and deactivation and reactivation processes of the polymer film on the metal film conductance. Relevant experiments, where the technique was employed to study the redox site distributions at the metal|polymer interface, during oxidation, deactivation and degradation of the polymer, were specially considered. The simple scattering model to explain surface resistance changes of a thin metal film coated with a poly(o-aminophenol) film is outlined on the basis of the specularity parameter, which represents the probability of an electron being reflected specularly or diffusely at the metal film surface. Information obtained by means of surface resistance is compared with that obtained by employing more traditional techniques such as cyclic voltammetry and rotating disc electrode voltammetry. Keywords: Degree of oxidation, Metal-polymer interface, Poly(o-aminophenol) films, Scattering model, Surface Resistance

Novel high‐performance polymer memory devices containing (OMe)2tetraphenyl‐p‐phenylenediamine moieties

AbstractThe functional polyimide (OMe)2TPPA‐6FPI (PI) and the polyamide (OMe)2TPPA‐6FPA (PA) consisting of electron‐donating N,N′‐bis(4‐aminophenyl)‐N,N′‐di(4‐methoxylphenyl)1,4‐phenylenediamine [(OMe)2TPPA‐diamine] for memory application were prepared in this study. These polyimide and polyamide memory devices were fabricated with the sandwich configuration of indium tin oxide (ITO)/polymer/Al, and could be switched from the initial low‐conductivity (OFF) state to the high‐conductivity (ON) state with high ON/OFF current ratios of 107 and 109, respectively. PI exhibited dynamic random access memory (DRAM) performance, whereas PA showed static random access memory (SRAM) behavior. To get more insight into the memory behaviors of these two different types of polymer memory devices, molecular simulation on the basic unit was carried out. Furthermore, the differences of highest occupied molecular orbital (HOMO) energy level, lowest unoccupied molecular orbital (LUMO) charge density isosurfaces, dipole moment, and linkage conformation between PI and PA were found to affect the volatile memory behavior. Both polymer memory devices revealed excellent stability with long operation time of 104 s at continuous applied voltage of ‐2 V. The effect of polymer thickness on the volatile memory behavior of PA was also investigated in this study. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

Polymeric materials for Solar Sail: The combined effects of polymer thickness, radiation, and temperature

ABSTRACTThe feasibility and the performance of solar sail depend critically on the availability of light materials and extremely thin polymeric films. The main requirements imposed on solar sail materials are analyzed in depth. The potential effects of the space environment are discussed in detail, with emphasis on the radiation-temperature-polymeric film thickness relationships. It is shown that the radiation component of the space environment triggers two competing degradation processes (erosion and depolymerization) and that both processes act towards the decrease in the glass transition temperature.

Effects of polymer thickness on the potentiometric pH responses of polypyrrole modified glassy carbon electrodes

The potentiometric pH response of electropolymerized polypyrrole modified glassy carbon electrodes as a function of polymer film thickness was examined. Electrodes coated with thicker polypyrrole films showed mixed potentiometric responses toward both cationic and anionic species, while thinner polypyrrole films (<2 μm) showed good linear response to pH changes for the pH range between 2 and 12. The possible mechanism for such behavior was discussed.

Surface-assisted formation of anisotropic dye molecular films

Dichroic dye layers were fabricated by spin coating of an aqueous dye solution on a thin film of an azobenzene polymer which was exposed to linearly polarized light in advance. The effect of polymer thickness on the dichroism and surface morphology of the dye layers were described.

Computer And Experimental Modelling Of TheContact Behaviour Of Prosthetic Knee Implants

Recent experience with prosthetic knee implants has shown that despite the widespread success of the surgical procedure and the restoration to activity it provides to patients suffering from arthritic disorders, certain key design problems remain to be solved. Perhaps the most serious of these problems is the high wear rate of the polymeric insert in the tibial component of the joint replacement. This high wear rate has been attributed to high levels of contact stress at the metal to polymer interface and also to the fact that this contact stress condition can cause the polymer surface to oscillate from tension to compression during the sliding and rolling motions which occur at the joint during normal walking. These oscillating stresses can induce fatigue type failures in the polymer. In order to obtain a better understanding of these contact conditions an experimental and theoretical investigation of the contact situation has been undertaken. The investigation involved the use of embedded strain gauges to evaluate subsurface stresses in an experimental model of the contact condition occuring at the implant surfaces. Both normal contact loads and normal contact loads coupled with sliding loads were studied as this combined loading situation is known to occur during the movement of the knee. In addition, the experimental model was simulated using Finite Element Analysis (MARCK6.2, Marc Analysis Research Corp.) and the results of the two procedures were compared. The Finite Element method was also used to critically examine a number of parameters associated with the contact behaviour of the UltraHigh Molecular Weight Polyethylene (UIIMWPE) tibial component of knee implants, both in two-dimensions and in three-dimensions. The effect of polymer thickness on contact stress levels was critically examined and it was found to be important. The sliding action which occurs at the knee joint was also found to influence the contact stress levels in the implant polymer. In almost all recent designs of total knee joint implants, a metallic tray is used for retaining and supporting the UIIMWPE component in the tibial implant. Certain design features associated with the metal tray were investigated to assess their influence on the contact stress levels in the polymeric insert and the results of the study indicated that the metal tray may have a major influence on the long-term performance of the implant. Transactions on Biomedicine and Health vol 4, © 1997 WIT Press, www.witpress.com, ISSN 1743-3525