ABSTRACT
The idea to incorporate organic dyes into polymer materials has attracted the attention of scientists for a long time. This interest joins the efforts of researchers from the different fields of physics, chemistry, biology, and high technology. Among the various studies related to the "dye-in-polymer" field, three major approaches may be considered. The first approach is connected with the investigation of the physical and chemical properties of polymers themselves using a fluorescence probe technique. In this case dye molecular probes have become a very powerful tool for studying various phenomena in synthetic and natural polymers. This is due to the high sensitivity of spectral parameters of the dyes to their microenvironment. Different probe methods are explored, including steady-state luminescence (exploring changes in the quantum yield of emission, halfwidth, and band shapes), time-resolved measurements (analysis of fluorescence decay kinetics), and fluorescence depolarization methods (especially, time-resolved anisotropy decay). Many investigations have been made to characterize molecular mobility and chain dynamics [1], glass transition temperature (T g) for a variety of polymers and copolymers [2], relaxations at different temperatures, which involve the motions of both long and short segments of the polymer chain [3], viscosity of the microenvironment [4], and free volume effects [5]. It was shown that in amorphous polymers their microviscosity is less then their macroviscosity by many orders of magnitude. In particular, high segmental mobility is in a highly elastic state (at temperatures above T g), which is determined by the existence of microcavities of free volume inside the matrix and by the essential increase in their size in the elastic state compared with the glassy state [5]. It is now well known that the main factors that influence the rate 236of photophysical and photochemical reactions in polymers are the free volume size at a given temperature and the size of molecular groups or the scale of their motions relative to the free volume size.
