Mechanical stretch modification

Recently, Genzer and coworkers [85] presented an interesting new approach for the preparation of stable silane-based SAM systems. As a substrate, cross-linked polydimethylsiloxane (PDMS) was oxidized by UV/ozone treatment to yield a thin sihcon dioxide surface. The surface was then treated with fluorinated alkyltrichlo-rosilanes from the gas phase while being mechanically stretched by a certain length Ax. After modification, the elastomer was allowed to relax resulting in a mecdianically assembled monolayer (MAM) at the surface (Fig. 9.8). 

Mechanical stretching of ceU membranes can be achieved by nanotechnological approaches and it can direct and control the intracellular signaling and differentiation of stem cells 136]. Modifications made to the spatial distribution or cytoskeletal re-organization provide physical impetus, whereby the mechanical deformation becomes translated into biochemical responses [37]. When the cells encounter... 

In the second variant of SHMM the investigated filaments were subjected to tensile stresses with different values under certain constant temperatures. The simultaneous heat mechanical samples modification was carried out using an apparatus created in our laboratory. The device involves a movable cylindrical oven located on the horizontal rails and a setup for the sample deformation reading. The heat-mechanical treatment begins when the preheated oven was rapidly shifted around the studied PET bundle that was simultaneously stretched with the needed strain stress. The experiment involves annealing of an as-spun PET yarns at four different temperatures in a narrow temperature range from 80 "C to 95 "C closely above its glass transition temperature while they are subjected to a well-defined tensile stress. 

Another apparatus for general biaxial extension testing, illustrated in Fig. 8, was built at our laboratory27). A square sheet of rubber, 11.5 cm long and 1 mm thick, is clamped at the edges by several pieces of movable chucks and stretched biaxially by means of the two bars that can be displaced separately bade and forth by a servo-meachnism. Tensile forces acting on the sheet in the stretching directions are transmitted to the bars and measured by two transducers mounted at the ends of each bar. After many modifications and improvements on the mechanical and electric parts,... 

Figure 4.2 shows the reaction coordinate diagram for this mechanism. The carbocation is a real intermediate and thus lies at an energy minimum energy maxima occur both when the C—X bond is stretched, and when the C—Y bond is formed. This process will be considered in detail in Chapter 5. A number of modifications of the original Ingold Sw 1 mechanism must be made to accommodate the results of more recent investigations. 

Such information offers an opportunity to study details of the fibrillation mechanism. The fibers formed by stretching the spherulitic polymer representing nothing other than ribbon formations plastically deformed and oriented towards the mechanical stress that is released by comparatively weak mutual interconditions existing in an earlier formation (Figure 3). This behavior points to the existence of some weak surfaces in the crystalline polymers. Elements of the super-molecular structure detached by action of the external mechanical forces can slide on the weak surfaces. Evidence for the strain-destruction relationship must come from studies of the modification of the contact surfaces of two neighboring spherulites under mechanical stress. 

Very large concentrations of plasticizers are used to produce permeable films and films with smface modification. In these cases, - plasticizer may consist up 70% of initial composition. This mixture is then extraded, plasticizer is removed by extraction and film is stretched to improve mechanical properties of microporous or surface modified film. 

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