Naslov
ESR-Spin Probe Study of Nanocomposite Polymer Materials

Autori
Valić, Srećko ; Lekić, Andrica ; Meera, A.P. ; Jacob, John ; Sabu, Thomas

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
Proceedings of ICNP-2007 / Sabu, Thomas - Kottayam : Institute of Macromolecular Science and Engineering, 2007, 27-28

Skup
International Conference on Nature Polymers, Bio-polymers, Bio-materials, their Composites, Blends, IPNs and Gels: Macro to Nano Scales

Mjesto i datum
Kottayam, Indija, 19.11.2007. - 21.11.2007

Vrsta sudjelovanja
Pozvano predavanje

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
ESR ; spin probe ; natural rubber ; nanofiller

Sažetak
Electron spin resonance (ESR) spectroscopy is a technique commonly used in studying polymer systems during last decades. This technique gives the information about molecular dynamics and matrix structure on the level of a chain segment. ESR spectroscopy is particularly successful in studying inhomogeneous polymer systems, like for example natural rubber. The large number of polymer materials does not possess stable paramagnetic centers and therefore, various nitroxide free radicals are usually used in order to investigate such materials by ESR. A nitroxide radical can be introduced in a polymer matrix by diffusion during the swelling of a polymer in a nitroxide solution. Such an application of nitroxides in ESR spectroscopy is known as spin probe method. In the present study, this method has been used to investigate the segmental dynamics and matrix structure of rubber nanocomposite materials and interpenetrating polymer networks. Natural rubber (NR) filled with the nanosilica particles having a diameter of 13 nm was crosslinked by sulphur. The sulphur content was constant and equal 2.5 phr in all samples. The amount of nanosilica was varied from 5 phr to 20 phr. ESR measurements were performed with the nitroxide radical 4-hydroxy-2, 2, 6, 6-tetramethylpiperidine-1-oxyl. The spin probe was incorporated in the material by swelling the samples in the toluene probe solution. Spectra were measured in a wide temperature range from -100 °C to 80 °C. ESR spectra observed in the vicinity of T5mT, the temperature related to the glass transition temperature, consist of the broad and narrow component characteristic for the slow and fast motion of the spin probe, respectively. The spectral shapes strongly depend on the nanosilica content. In fact, the higher amount of nanosilca results in higher amount of the broad spectral component. This suggests that an addition of nanosilica particles leads to the restriction in segmental motions. An influence of the coupling agent on the motional behavior of NR chain segments was also investigated. The narrow component, indicating fast segmental motions, which is neatly pronounced in the spectrum of the sample without coupling agent, almost disappears by an addition of 4 phr of the coupling agent. According to these ESR results, it can be concluded that the interaction of the nanoparticles with NR chain segments become more efficient when the coupling agent is present in the matrix. Additional ESR measurements were made with the interpenetrating polymer networks (IPNs) composed of natural rubber and poly(methyl methacrylate) (PMMA). The results have shown that the local motions of the NR chain segments strongly depend on the amount of PMMA component. The higher amount of PMMA leads to the restriction in dynamics of the polyisoprene chain segments.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

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