engleski

ESR - Spin Probe Method in Studying Some Multiphase Polymer Systems

Electron spin resonance (ESR) spectroscopy also known as electron paramagnetic resonance (EPR) provides the ability to detect unpaired electrons. Mostly, polymers do not possess unpaired electrons and their study using ESR requires the incorporation of paramagnetic centers in the samples. The most frequently used carriers of paramagnetic centers that are used to study polymers are nitroxyl radicals. Two approaches are known: (i) radicals can be covalently attached to a polymer chains or (ii) they can be introduced mechanically (by diffusion) into a polymer matrix. The former is named spin labeling and the latter spin probe method. A short overview of these two methods will be given. The use of spin probe method will be illustrated through recent studies of natural rubber (NR) doped with nanoparticles of silica and organically modified clay (montmorillonite). The results of influence of type and amount of nanofiller and coupling agent on motional behavior of polyisoprene chains will be presented. The effect of matrix composition, structure, crosslink density and molecular weight of semi-interpenetrating polymer networks (semi-IPNs) composed of poly(isoprene) and poly(methyl methacrylate) on dynamic behavior of chain segments will be discussed. ESR spectra of spin probe diffusing in a lamellar phase of polystyrene-polydimethylsiloxane observed in a wide temperature range will be shown and analyzed.

ESR - spin probe; segmental dynamics; inhomogeneity

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