Sulfonated Styrene-(ethylene-co-butylene)-styrene/Montmorillonite Clay Nanocomposites: Synthesis, Morphology, and Properties

Sulfonated styrene-(ethylene-butylene)-styrene triblock copolymer (SSEBS) was synthesized by reaction of acetyl sulfate with SEBS. SSESB-clay nanocomposites were then prepared from hydrophilic Na-montmorillonite (MT) and organically (quaternary amine) modified hydrophobic nanoclay (OMT) at very low loading. SEBS did not show improvement in properties with MT-based nanocomposites. On sulfonation (3 and 6 weight%) of SEBS, hydrophilic MT clay-based nanocomposites exhibited better mechanical, dynamic mechanical, and thermal properties, and also controlled water–methanol mixture uptake and permeation and AC resistance. Microstructure determined by X-ray diffraction, atomic force microscopy, and transmission electron microscopy due to better dispersion of MT nanoclay particles and interaction of MT with SSEBS matrix was responsible for this effect. The resulting nanocomposites have potential as proton transfer membranes for Fuel Cell applications

Dynamic Mechanical Properties of Annealed Sulfonated Poly(styrene-b-[ethylene/butylene]-b-styrene) Block Copolymers

Solution cast films of lightly sulfonated styrene-b-[ethylene-co-butylenel-b-styrene, (sSEBS) block copolymers were annealed for various times at 120 degreesC and thermal transitions are evaluated using dynamic mechanical analysis. Increased annealing time and increase in degree of sulfonation increases T-g for the PS phase while T-g for the EB phase is practically unchanged, and in some cases, there is suggestion of a relaxation due to EB-PS inter-phases. Annealing has a minor effect on the rubbery plateau storage modulus. Thus, annealing primarily alters the PS block phase. EB-PS phase separation appears to be refined with increasing SO3H content. The region of rubber elasticity extends to higher temperatures with increased degree of sulfonation. A high temperature dynamic mechanical transition that is tentatively attributed to disruption of SO3H-rich sub-domains within the PS block domains shifts to higher temperature with annealing. (C) 2004 Elsevier Ltd. All rights reserved

Self-Assembled Organic/Inorganic Hybrids As Membrane Materials

Self-assembled organic-inorganic membranes that are achieved via sol-gel polymerizations of silicon alkoxides around sulfonated outer blocks of polystyrene-[soft block]-polystyrene block copolymers during film formation are described. The nanoscopic morphologies, molecular structure of very hydrophilic silicate nanophases, and methods of studying the structure and transport of water through these membranes are discussed. These hydrocarbon-based hybrids are contrasted with the earlier successful efforts to generate Nafion((R))/silicate nanocomposite membranes produced in similar fashion, but using pre-formed films. (C) 2004 Elsevier Ltd. All rights reserved

Dynamic Function Optimization: The Moving Peaks Benchmark

Many practical, real-world applications have dynamic features. If the changes in the fitness function of an optimization problem are moderate, a complete restart of the optimization algorithm may not be warranted. In those cases, it is meaningful to apply optimization algorithms that can accommodate change. In the recent past, many researchers have contributed algorithms suited for dynamic problems. To facilitate the comparison between different approaches, the Moving Peaks (MP) function was devised. This chapter reviews all known optimization algorithms that have been tested on the dynamic MP problem. The majority of these approaches are nature-inspired. The results of the best-performing solutions based on the MP benchmark are directly compared and discussed. In the concluding remarks, the main characteristics of good approaches for dynamic optimization are summarised. Dynamic function optimization is an active research area. Over the years, many different algorithms have been proposed to solve various types of dynamic optimizatio