Fluorescence polymer blends

Some of the most relevant applications of fluorescence spectroscopy to the characterization of intrinsically fluorescent polymer blends are discussed in the following subsections. 

Thus, for the investigation of buried polymer interfaces, several techniques with molecular resolution are also available. Recently NMR spin diffusion experiments [92] have also been applied to the analysis of a transition zone in polymer blends or crystals and even the diffusion and mobility of chains within this layer may be analyzed. There are still several other techniques used, such as radioactive tracer detection, forced Rayleigh scattering or fluorescence quenching, which also yield valuable information on specific aspects of buried interfaces. They all depend very critically on sample preparation and quality, and we will discuss this important aspect in the next section. 

A new electrofluorescent switch was prepared with an electroactive fluorescent tetrazine blend of polymer electrolyte <06CC3612>. The structure and magnetic properties of the stable oxoverdazyl free radical 6-(4-acetamidophenyl)-1,4,5,6-tetrahydro-2,4-dimethyl-... 

Confocal fluorescence microscopy has been extensively used in cell biology. Single living cells can indeed be studied by this technique visualization of organelles, distribution of electrical potential, pH imaging, Ca2+ imaging, etc. (Lemasters, 1996). Interesting applications in chemistry have also been reported in the fields of colloids, liquid crystals and polymer blends. 

In the last years, the fluorescence probe technique has become an increasingly importance in many fields of material science because this technique opens up the possibility to examine the microscopic environment of different materials. First, this method has been successfully applied in the field of polymer science to study the polymer building process [1], the relaxation behavior of linear [2] and crosslinked polymers [3], polymer blends [4], and the interaction between polymer chains and various solvents[5]. 

These early studies demonstrated that excimer fluorescence is a useful addition to the battery of experimental tools available to study solid state polymer blends. However, the longer range goal of explaining the significance of the absolute value of R was not realized because there was insufficient companion information about the thermodynamics of the blends. The PS/PVME blend does not suffer from this limitation, and thus provides an excellent system for characterization of the photophysies under conditions for which miscibility or immiscibility are firmly established. In this section we examine results for PS/PVME as well as more recent work on dilute blends containing P2VN that are believed to be miscible. 

Energy transfer in polymers has been studied in the pure solid state, in heterogeneous systems (e.g. polymer blends), in liquid solutions and in solid solutions. The last case, which will be considered here, provides relatively simple and clear experimental conditions since interactions between the macromolecules can be excluded by dilution and molecular movement is severely restricted by low temperature and rigid environment. Thus, excitonic energy transfer can be studied without competing molecular movement. The luminescence of dilute, solid solutions of aromatic polymers is not dominated by excimers - in sharp contrast to the other modes of observation - so that side group fluorescence and phosphorescence can be observed. This does not mean, however, that exciton trapping processes are absent in these systems. 

Previous experiments measuring fluorescence depolarization arising from excitation transport among chromophores on isolated guest colls in solid polymer blends demonstrated the feasibility of determining the relative size of individual chains in various host environments (18). The ability of these experiments to... 

Similar strategies have been followed to obtain white emission from fluorescent polymer systems and phosphorescent ones as well. However, polymer blends have generally been used to fabricated WPLEDs (as multilayer spin-coated polymer assemblies are difficult to obtain owing to close solubility parameters of materials), such as red, green, blue light-emitting three-polymer systems [257-259] and two-... 

Measurement of transient concentration profiles of deuterated polymers in polymer blends using forward recoil spectroscopy Measurement of transient concentration profiles of fluorescently labeled molecules in capillary tubes using epifluorescence microscopy Measurement of transient concentration profiles of fluorescently labeled molecules in biological tissues using epifluorescence microscopy Fluorescence recovery (or redistribution) after photobleaching (FPR)... 

The second class contains a fluorescent chromophore, also referred to as a fluorophore, on every repeat unit, either pendent to the chain or in the backbone. Examples of compounds having chromophores pendent to the chain are polystyrene and poly(2-vinylnaphthalene), both of which have been extensively studied as components of polymer blends (7-i3). Compounds having chromophores in the backbone are represented by an aromatic polyamide, polyester (14), or polyurethane (15). 

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