Future Outlook and Concluding Remarks

Falconer, J.L., Noble, R.D., and Sperry, D.P. (1995) Catalytic Membrane Reactors, in Membrane Separations Techndogy Principles and Applications, Chapter 14 (eds R.D.Noble and S.A. Stern), Elsevier, Amsterdam, pp. 669-712. 

Sanchez, ). and Tsotsis, T.T. (2002) Catalytic Membranes and Membrane Reactors, Wiley-VCH Verlag GmbH, Weinheim. 

(1996) Inorganic Membranes for Separation and Reaction, Elsevier, Amsterdam. 

Baerlocher, C. and McCusker, L.B. (2008) Database of zeolite structures, www.iza-structure.org/databases/ (visited November 2008). 

Taramasso, M., Perego, G., and Notari, B. (1983) Preparation of porous crystalline synthetic material comprised of silicon and titanium oxides. US Patent 4,410,501. 

Optical spectroscopy (IR/NMR/Raman) has been extremely useful in the study of the sulfur and peroxide crosslinking chemistry of elastomers, especially that of EPDM. The 

For sulfur vulcanisation of EPDM it was shown that the relative ENB conversion (20 to 60%) is higher than often assumed. The absolute ENB conversion was shown to be governed by the vulcanisation recipe and to be independent of the EPDM type. For the ISO 4097 [82] recipe the average length of the sulfur crosslinks is 2.7 sulfur atoms. The number of converted ENB units per sulfur bridge is 2.0, indicating that crosslinks are formed predominantly. In a preliminary study it was shown that the mechanical properties of unfilled sulfur-vulcanised amorphous EPDM are determined by the chemical crosslink density. Clearly, these studies should be extended to other vulcanisation recipes and completely formulated compounds. Vulcanisation kinetics should be studied, preferably at different temperatures. 

The effect of co-agents in the peroxide-curing of EPDM is very similar to the effect of third monomers. It was concluded that the pendent unsaturation of the third monomer acts as a co-agent, i.e., the amount of third monomer governs the amount of chemical crosslinks formed by macroradical addition reactions via the unsaturated moiety of the third monomer, whereas the amount of peroxide governs the amount of crosslinks formed by macroradical combination reactions. 

For IR and Raman spectroscopy studies there is a clear limitation when large amounts of carbon black are applied, as is common practice in technical rubber goods. In that sense the applicability of Raman and IR spectroscopy seems to be surpassed by solid-state 13C 

NMR spectroscopy and solid-state and 13C NMR relaxation-time experiments. However, the sensitivity of solid-state 13C NMR is not as high as that of Raman and IR spectroscopy. For instance, solid-state 13C NMR of sulfur-vulcanised EPDM could only be performed when the ENB unsaturation of EPDM was fully isotopically enriched with 13C NMR [124]. 

We have studied the electronic properties of the polythiophenes in relation to their structural and conformational characteristics. Their electronic properties come out of the TT-conjugated system extended along the polythiophene backbone. Since the electronic state is strongly coupled to the backbone conformation, a variety of electronic properties show themselves depending on the conformations of polymer chains. 

The structural variation can be measured as against a perfect crystal lattice where the polythiophene backbones satisfy the translational symmetry along the chain direction and form the herringbone structure spreading two-dimensionally perpendicular to that direction. In this respect polythiophene derivatives, especially PATs, provide a variety of peculiar structures. Examples include a bundled structure in which the rodlike polymer chains form nearly the face-to-face configuration. Helical and superhelical structures can be noted as well. The polymers having chiral side chains even exhibit stereomutation associated with the main-chain chirality. 

The interplay of the electronic structure and the backbone conformation is observed as chromisms both in the solid state and solution. The reversible appearance and disappearance of the fine structure linked to the peak shift in the electronic spectra obviously demonstrate that the order-disorder transformation in the backbone conformation plays an important role. 

Spectroscopic studies including ESR, EVS, and UV-Vis. enable the detailed characterization of the charge storage configurations and show that in most cases the bipolarons are the most dominant excitations in the polythiophenes. At the same time, anisotropic features of the charge excitations are quite evident. This has been confirmed by the dichroic IR measurements of the aligned films of the polythiophenes. 

The studies of the conducting polymers in solution offer a good opportunity to inspeet the eharge transport limited within a single isolated polymer chain. Exclusively the intrachain electronic processes can be studied when the conducting polymers are dispersed dilutely in the solution. The unique technique of FEES has verified the presence of two levels of intrachain transport processes, in which defects or disorder plays a specific role. 

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Concluding Remarks and Future Outlook, 31 Suggested Further Reading, 32... 

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