Fluorescence polymer blend systems

By contrast, in fluorescence microscopy the image is formed by collecting the fluorescence emissions from a specimen. Because the fluorescence emitted from a specimen can provide many types of information, fluorescence microscopy has been used widely for the structural analysis of polymer blend systems. 

In this chapter, the application of fluorescence imaging techniques to the structural analysis of polymer blend systems is discussed, and recent developments in fluorescence microscopy are described. 

Fluorescence microscopy is an effective technique for studying the structure of polymer blend systems, as it not only reveals the quantitative spatial distribution of polymer components but also provides molecular information from the fluorescence spectrum and decay curve. Real-space observation in three dimensions with high time-resolution can reveal the detailed structure and formation process of the... 

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. 

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-... 

Ultraviolet and fluorescent microscopy has been applied to a variety of polymer systems to investigate changes of morphology and composition on the scale of 0.25 ym upwards. Studies are briefly described on the behaviour of stabilisers in polypropylene, diffusion of additives in polymers, spherulite morphology, polyolefin oxidation, inhomogeneities in epoxy resins and polymer blends. 

Description of the excimer photophysics for a two-phase system presented by Wandelt and co-workers [66] are based on both the two-phase model assumptions and the experimental results. The two-phase model describes the results of the experimental studies of photoenergy migration in heterogeneous solid-state polymer blends by Frank and collaborators [68, 69]. Tao and Frank [69] used three-dimensional electronic excitation transport to interpret the ratio of excimer to monomer fluorescence for poly-2-vinylnaphthalene with polycyclohexyl methacrylate. The assumptions of the two-phase model are ... 

---