engleski

ESR - Spin Probe Method in the Study of Inhomogeneous Polymer Systems

Electron spin resonance (ESR) – spin probe method has been used several decades as a powerful tool in the study of various organic, inorganic and biological systems. Its simplicity in comparison with the spin label method makes it very popular and frequent. This method is particularly useful in the study of polymer systems which do not possess intrinsic paramagnetism and therefore do not give an ESR signal. A detailed analysis of ESR spectra of the spin probe in such systems makes it possible to obtain fruitful information about local molecular dynamics and matrix structure. The incorporation of spin probe in a polymer matrix is usually carried out simply by dissolving or swelling the polymer in a probe solution at constant temperature during couple of days, giving the possibility to solvent to evaporate slowly. Consequently, probe molecules remain trapped in the polymer matrix. This process is followed by an annealing of the sample in vacuum at an elevated temperature, until the constant mass of the sample. During the annealing, probe molecules can redistribute so that they occupy the thermodynamically most favorable sites inside the matrix. The aim of this work is to demonstrate how the conditions of probe incorporation process may influence the ESR results of spin probes diffusing in an inhomogeneous polymer matrix. Particularly, effects of the solvent quality, probe incorporation temperature and annealing temperature will be presented and discussed.

ESR ; EPR ; Spin probe ; Incorporation conditions ; Polymer ; Homogeneity ; Dynamics

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