Block polymer, conductive hybrids

We measured the electrical conductivity of Pt-C nanocomposites using two-point measurements. In a representative example the NP-polymer hybrid had a conductivity of 2.5 mS cm-1, which increased to 400 S cm-1 upon pyrolysis. Despite the presence of carbon, to the best of our knowledge this value represented the highest electrical conductivity yet measured for ordered mesoporous materials derived from block copolymers. This discovery creates a potential pathway to a new class of ordered mesoporous metals made from nanoparticles of different elements and/or distinct compositions. Such nano-heterogeneous mesoporous metals may have a range of exceptional electrical, optical, and catalytic properties. 

In this section, some peculiarities of copolymerization conducted in CRP systems will initially be discussed and then examples of various types of copolymers will be provided. They will include statistical, gradient, and alternating copolymers, as well as block and graft copolymers. Some special systems will be also presented and they will include preparation of stereoblock copolymers, and various hybrid materials formed by either mechanistic transformation or by growing well-defined polymers from flat, colloidal, or irregular surfaces. 

Schrotter I.C., Smaihi M., Guizard C. Polyimide-siloxane hybrid materials influence of coupling agent addition on microstructure and properties. J. Appl. Polym. Sci. 1996 61 2137-2149 Soler-Dlia G.I., de A.A., Crepaldi E.L., Grosso D., Sanchez C. Block copolymer-templated meso-porous oxides. Cnrr. Opin. Colloid Interface Sci. 2003 8(1) 109-126 Steele B. Ceramic Ion Conducting Membranes and Their Technological Apphcation. C.R. Acad. Sci. Paris 1998, Series lie. Title 1, pp. 533-543... 

Proton conductivity measurements were performed by AC impedance technique. The proton conductivities for all the membranes increased with increase in temperature from 30°C to 100°C as seen in Figure 10.16. It is noteworthy that the proton conductivity increases with increase in SWA content from 5 to 10 wt% and decreases at 15 wt% SWA. Higher content of SWA (>10 wt%) in cross-linked CS-PVA blend disrupts the proton conduction path by blocking the voids of polymer matrix and decreases its proton conductivity, which may be also attributed to the water sorption data. The methanol crossover for the membranes is measured in situ in fuel cells under OCV condition at 70°C. The methanol crossover flux is lower for CS-PVA-SSA-SWA (10 wt%) (about 3.3 x 10" mol s" cm- ) hybrid membranes in comparison with Nation 117 and other membranes. In addition, the electrochemical selectivity of CS-PVA-SSA-SWA (10 wt%) has reached to 2.69 x 10 S cm- s. 

Polymer materials are ubiquitous in our daily life. They often consist of more than one species of polymers and, therefore, can be called multicomponent systems, for example, polymer blends and block copolymers. Because of the repulsive interaction between the constituent polymers, multicomponent polymer materials often show phase separation. Organic-inorganic composites are another class of polymer-based multicomponent materials that have attracted considerable interest from researchers because they often exhibit unexpected properties synergistically derived from the constituents. Nanometer-sized particulate fillers, for example, carbon black (CB) and silica (Si) nanoparticles, are known to form hybrids with organic polymers, which show a significant increase in their static and dynamic moduli, strength, and thermal and electrical conductivities. 

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