engleski

ESR - Spin Probe Study of Some Nanocomposite Polymer Materials

Nitroxyl radicals of various size, shape and polarity are often used for the study of polymer systems by electron spin resonance (ESR)1. Spin probe method supposes that they are incorporated in a polymer matrix by diffusion and that there is no chemical bond between the nitroxyl radical and polymer chain. The use of this method will be illustrated through recent studies of natural rubber (NR) and its synthetic analogues doped with nanoparticles of silica and organically modified clay (montmorillonite). The amount of nanoparticles was varied from 1 phr to 10 phr, while the crosslinking density was constant. An influence of type and amount of nanofiller on segmental motions was investigated. The effect of coupling agent on motional behavior of polyisoprene matrix was also studied. The influence of matrix composition, structure, crosslink density and molecular weight of semi-interpenetrating networks (semi-IPNs) composed of poly(isoprene) (PI) and poly(methyl methacrylate) (PI/PMMA) was studied by various techniques. Spin probe method was shown to be a powerful tool in monitoring small changes in motional behavior of chain segments. Particularly interesting are dynamic changes caused by different molecular weight and crosslinking density of polyisoprene component for samples having the same composition. The results obtained by ESR – spin probe method are supported by those obtained with other techniques (DMA, and solid state NMR).

ESR - spin probe; rubber nanocomposite; semi-IPNs

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