Proton conducting membranes based on Poly(2,5-benzimidazole) (ABPBI)–Poly(vinylphosphonic acid) blends for fuel cells

Polymer electrolyte membranes (PEM) were fabricated by blending of Poly(2,5-benzimidazole) (ABPBI) and Poly(vinylphosphonic acid) (PVPA) at several stoichiometric ratios with respect to monomer repeating units. The characterization of the membranes were carried out by using Fourier-transform infrared spectroscopy (FT-IR) for inter-polymer interactions, scanning electron microscope (SEM) for surface morphology as well as homogeneity and thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) for thermal properties. Water uptake measurements were made to investigate the swelling character the blends that was changed with PVPA composition. The spectroscopic measurements and water uptake studies suggested the complexation between ABPBI and PVPA that inhibited dopant exclusion up on swelling in excess water. Proton conductivities of the hydrated and anhydrous samples were measured using impedance spectroscopy. Although the proton conductivity of the blends was lower in the anhydrous state such as 1.8 × 10⁻⁶ S/cm at 150 °C for ABPBI:PVPA with (1:2), it increased to 0.004 S/cm for ABPBI:PVPA (1:4) at 20 °C (RH = 50%).     

Investigation of liquid diffusion into contact lenses using an electron spin resonance technique

In this study, electron spin resonance (ESR) spectroscopy was used for the first time to investigate liquid diffusion into contact lenses. As contact lenses are not paramagnetic substances, they were labeled with nitroxide spin probes to get an ESR spectrum. Thus, it gives a solid spin‐labeled ESR spectrum. The shape and intensity of the ESR signals depend on the environment of these spin probes. The spin probe environment began to change from solid to liquid if liquid were dropped into the system. Consequently the ESR spectra began to change with time, too. By following these changes, three distinct steps were found. Their diffusion coefficients were determined to be 6.38 × 10^?8 cm²/s for the first step (rapid decay region) and 0.37 × 10^?8 cm²/s for the second step (slow decay region), and 2.50 × 10^?8 cm²/s for the third and last step (desorption region). © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2942–2946, 2006     

New type of anhydrous organic electrolyte based on carboxylic acid functional triazole as model system

The model system of dicarboxylic acid functionalized 1H-1,2,3-triazole-terminated alkyl oligomers is presented as a new approach for obtaining high proton conductivity in proton solvating heterocycles covalently bound via spacers. The model materials have been characterized by FT-IR and NMR spectroscopy. Thermal stabilities were examined with thermogravimetric analysis (TGA). Differential scanning calorimetry (DSC) was used to measure melting and crystallization temperatures. The influence of spacer length on proton conductivity was investigated by AC impedance spectroscopy. Analysis of conductivity and permittivity measurements revealed the contribution of local dynamics and proton mobility on conduction mechanism which gives rise to proton conductivities of up to 10^?5 S/cm at 120 °C in completely water-free pristine materials.     

New soluble azophenol polymers prepared by oxidative polycondensation

New azophenol polymers (P₁, P₂ and P₃) were synthesised by the oxidative polycondensation (OP) reaction of three different azophenol monomers in aqueous alkaline medium with NaOCl as the oxidant. The monomers and the polymers were characterised by elemental analyses, and UV‐visible, Fourier transform infrared, ¹H NMR and ¹³C NMR spectroscopic studies, which revealed that the polymers synthesised by OP are composed of oxyphenylene (C? O? C) and phenylene (C? C) units. The polymers obtained are soluble in dimethylformamide and dimethylsulfoxide. Average molecular weights of the polymers were determined by gel permeation chromatography. Additionally, P₂ and P₃ are soluble in water and methanol. On the basis of thermogravimetric analyses, 5 and 50% weight‐loss temperatures of the polymers were found to be 218, 700 (P₁), 263, 609 (P₂) and 100, 809 °C (P₃), respectively, suggesting a high thermal stability. Thermal analyses using differential scanning calorimetry revealed that the azophenol polymers are highly amorphous, and melting peaks were not observed in the heating cycles. This suggests that all the polymers are highly amorphous. The azophenol polymers show a reversible trans–cis–trans isomerisation process. These properties of the polymer could be promising for their technological usage. Copyright © 2007 Society of Chemical Industry     

A Newton-Raphson based strategy for exploiting latency in dynamic simulation

Latency [6] in dynamic simulation is a consequence of the difference between the dynamic behavior of different units that make up a flowsheet. Taking advantage of latency is essential to reduce the computation time in dynamic simulation. It is observed that in dynamic simulation there is a parallelism between the degree of dynamical activity of a unit and the computational effort required to realize this activity. An algorithm is presented to exploit this parallelism by avoiding some or all the steps involved in solving the corrector equations in the numerical integration process by the Newton-Raphson method. Unlike conventional ones, the proposed algorithm has no approximations built into it and solves the correct model of the flowsheet at each step of the integration. The algorithm is tested on the example problem and it is shown that significant savings in computation time can be achieved.     

Goal-driven blackboard control architecture based on extending partially complete general goal trees

A control architecture for goal-driven blackboard systems is introduced. The basic elements of the architecture are goals, policies, strategies, methods and knowledge sources. The basic control loop employs a bidding mechanism to determine the knowledge source to be executed at the current cycle. The architecture employs separate control and domain blackboards, and separate knowledge sources for the control problem and for representing the domain knowledge. The major characteristics of the architecture are that it has a simple and uniform structure, and that its basic control loop is based on a formal basis, namely, extending a partially complete general goal tree. The architecture is implemented in Smalltalk and tested on a multiple-task planning problem.     

Proton conduction promoted by 1H-1,2,3-benzotriazole in non-humidified polymer membranes

Heterocyclic protogenic solvents are promising candidates in production of proton conductive non-humidified membranes. In this work, 1H-1,2,3-Benzotriazole, BTri which is a novel protogenic solvent was incorporated into Nafion and polyvinylphosphonic acid, PVPA to produce novel anhydrous membranes. The composite membranes were characterized using FTIR, TGA and DSC. TGA results confirmed the thermal stability of the membranes and DSC results verified the homogeneity of the materials. The proton conductivity of these polymer electrolyte membranes with respect to BTri content was investigated. 1H-1,2,3-Benzotriazole promoted the proton conductivity of the membranes reaching approximately 10⁻³ S/cm at 150 °C, under anhydrous conditions. Cyclic voltammetry (CV) results demonstrated that 1H-1,2,3-benzotriazole has broad electrochemical stability domain.     

Analog active filter component selection with nature inspired metaheuristics

The most crucial design step for analog active filter design is the optimal selection of passive component values due to manufactured constants. Since the search on possible combinations in preferred values for capacitors and resistors is an exhaustive process, it has to be automated with high accuracy within short computation time. In this work, two nature inspired metaheuristics, differential evolution (DE) and harmony search (HS) algorithms are utilized for optimal filter design considering different topologies and manufacturing series. Simulation results show that as global optimization methods both DE and HS minimize the total design error and reduce the elapsed time with respect to previously utilized methods.