Pore structure and morphology

Evaluating Pore Structure and Morphology of Hydrocarbon-Conversion Catalysts... 

F. H. Collagen-based wound dressings—control of the pore structure and morphology. J. Biomed. Mater. Res. 1986, 20, 1219-1228. 

In contrast transmission electron microscopy (TEM) can in skilled hands yield detailed quantitative data on pore structure, and can even provide valuable information on the wet state of resins by plunge freezing such samples and microtom-ing on a cold stage [105]. To obtain quantitative information it is necessary to use advanced image analysis methodology which is extremely powerful [106]. Unfortunately the approach is time consuming and costly and can rarely be applied routinely in morphology studies. 

The transport properties across an MIP membrane are controlled by both a sieving effect due to the membrane pore structure and a selective absorption effect due to the imprinted cavities [199, 200]. Therefore, different selective transport mechanisms across MIP membranes could be distinguished according to the porous structure of the polymeric material. Meso- and microporous imprinted membranes facilitate template transport through the membrane, in that preferential absorption of the template promotes its diffusion, whereas macroporous membranes act rather as membrane absorbers, in which selective template binding causes a diffusion delay. As a consequence, the separation performance depends not only on the efficiency of molecular recognition but also on the membrane morphology, especially on the barrier pore size and the thickness of the membrane. 

A unique 3D porous structure is observed in the swollen hydrogel (Fig. 21), which is not determined in the unswollen state. Different pore sizes and morphologies between the surface and the interior of swollen hydrogels are visible [175]. 

Fig. 34 Example of mechanized mesoporous silica nanoparticles (MSNPs). SEM (a) and TEM (b) images show the structure and morphology of the MSNP platform [238]. (c) Structural formula of the a-cyclodextrin-based snap-top rotaxane that blocks the pores of an enzyme-cleavable mechanized MSNP. The stopper is connected to the stalk (dumbbell) by an ester or an amide bond [254]. (d) Release profile of rhodamine B from the snap-top MSNP. The addition of an esterase enzyme cleaves the ester bond, releasing the stopper, a-cyclodextrin, and cargo from the nanoparticles, which is monitored by the fluorescence intensity of rhodamine B. Controls employing an amide bond snap-top or deactivated enzyme do not release significant amounts of cargo...

Recently reported meso- and macroscale self-assembly approaches conducted, respectively, in the presence of surfactant mesophases [134-136] and colloidal sphere arrays [137] are highly promising for the molecular engineering of novel catalytic mixed metal oxides. These novel methods offer the possibility to control surface and bulk chemistry (e.g. the V oxidation state and P/V ratios), wall nature (i.e. amorphous or nanocrystalline), morphology, pore structures and surface areas of mixed metal oxides. Furthermore, these novel catalysts represent well-defined model systems that are expected to lead to new insights into the nature of the active and selective surface sites and the mechanism of n-butane oxidation. In this section, we describe several promising synthesis approaches to VPO catalysts, such as the self-assembly of mesostructured VPO phases, the synthesis of macroporous VPO phases, intercalation and pillaring of layered VPO phases and other methods. 

DVB were valid in this system as well. These concern the dependence of surface area and pore volume on the amount of diluent and cross-linker. The surface area increases with the amount of EDMA and goes through a maximum with increasing amount of diluent. Using cyclohexanol-dodecanol as a solvent-non-solvent pair, the factors of importance for the structure and morphology of the polymers were studied by experimental design [34]. In these experiments the concentration of the diluent mixture was varied between 20 and 77% (volume/total volume), the concentration of EDMA between 25 and 100% (volume/monomer volume), the concentration of initiator (AIBN) between 0.2 and 4% (w/w), the concentration of non-solvent (dodecanol), between 0 and 15% (v/v) and the polymerisation temperature between 70° and 90°C. The surface area (determined by nitrogen sorption), pore volume (determined by mercury porosimetry) (see Section 2.11.6.) and the mechanical properties were chosen as responses. 

Chemical, thermal, photochemical and structural stability one-step procedure at ambient or low temperature Control of pore size and morphology high electro chemical active surface area high conductivity suitable for development of miniaturized biosensor devices Suitable for miniaturization enhanced sensitivity low cost production (usually lithography)... 

Membrane characterization means the determination of structural and morphological properties of a given membrane. Because membranes range from porous to nonporous depending on the type of separation problem involved, different characterization techniques are required in each case. For example, in MF or UF membranes, fixed pores are present. MF membranes have macropores (pore diameter > 50 mn), while UF membranes have mesopores (2 mn < pore diameter < 50 nm). The pore size (and size distribution) mainly determines which particles or molecules are retained or pass through. On the other hand, for dense or nonporous membranes, no fixed pores are present and the material chemistry itself mainly determines the performance. 

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