Hemispherical structure

Fig. 4.4. This figure may be considered a window to a chemical aquarium. The core of each of the structures is carbon and most of the hemispherical structures attached to the core represent hydrogen atoms. When these molecules collide under appropriate conditions, either on the surface of a catalyst or with sufficient energy, the carbon core of two units will form covalent bonds, displacing hydrogen. The discharge chamber in the Miller-Urey experiment served to displace the hydrogen and thus to create active molecular species that would form larger covalent structures.

Photoresist Reflow Photoresist reflow is a method to generate 3D hemispheric structures for... 

Photoresist cylinders were then separately built by conventional lithography. In order to achieve large fluidic volume, thick photoresist AZIOOXT was chosen, and its patterned cylinders on the substrate were thermally treated on a hot plate. The reflow occurred at 120 °C in a period of 60 s. Sometimes, the organic solvent vapor surrounding the photoresist pattern can promote the reflow process. Figure 14a shows the SEM image for the photoresist mold, which smoothly joins hemispherical structure 2,200 pm in diameter and 167 pm in depth with the microchannel. 

It can be verified with similar calculations that the upper hemispherical structure is equally adequate, as well as the lateral structure of the reactor cavity (suitably reinforced by additional steel bars, within the limits of practical feasibility). 

The process of formation of complex block copolymer stmctures in 3D confinement has been elucidated for some selected PS-Z>-PMMA copolymers. Introduction of a nonsolvent into the spherical nanoparticles yielded hemispherical structures of onionlike morphology. Such structures may be viewed as a result of double confinement consisting of the outer surfactant double layer and the inner nanophase separation between the block copolymer and the nonsolvent for both blocks. This concept allows targeting the nanoparticle shape as well as the iiuier particle morphology (ranging from simple core-shell to onion-Uke to patched structures), which may find application for encapsulation of various substrates with predetermined release characteristics. 

It should be noted that in this table the end effects in elongated micelles due to capping by surfactant molecules which leads to an ellipsoidal or spherocylindrical (cylinder capped by hemispheres) structure are neglected. This will, however, change both mean and Gaussian curvatures, to an extent that depends on the relative surface area of cap and tubular parts. 

Recently, Durant et al. [55] developed a mechanistic model based on the classic Smith-Ewart theory [48] for the two-phase emulsion polymerization kinetics. This model, which takes into consideration complete kinetic events associated with free radicals, provides a delicate procedure to calculate the polymerization rate for latex particles with two distinct polymer phases. It allows the calculation of the average number of free radicals for each polymer phase and collapses to the correct solutions when applied to single-phase latex particles. Several examples were described for latex particles with core-shell, inverted core-shell, and hemispherical structures, in which the polymer glass transition temperature, monomer concentration and free radical entry rate were varied. This work illustrates the important fact that morphology development and polymerization kinetics are coupled processes and need to be treated simultaneously in order to develop a more realistic model for two-phase emulsion polymerization systems. More efforts are required to advance our knowledge in this research field. 

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