Regularity modes in Raman spectra of polyolefins: Part II. Polyethylene and ethylene copolymers |
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| Affiliation: | 1. Prokhorov General Physics Institute, Russian Academy of Sciences, Vavilov St. 38, 119991 Moscow, Russia;2. Department of Physics and Earth Sciences, Jacobs University Bremen, Campus Ring 1, 28759 Bremen, Germany;3. Semenov Institute of Chemical Physics, Russian Academy of Sciences, Kosygin St. 4, 119991 Moscow, Russia;4. Topchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences, Leninsky Pr. 29, 119991 Moscow, Russia;1. Aix Marseille Univ., Univ. Avignon, CNRS, IRD, IMBE, Marseille, France;2. Aix Marseille Univ., CNRS, ICR, Case 551, 13397 Marseille, France;3. Vorozhtsov Novosibirsk Institute of Organic Chemistry Office 312, 9 Prospect Academican Laurentiev, 630090 Novosibirsk, Russia;4. Sartorius Stedim FMT S.A.S, Z.I. Les Paluds, Avenue de Jouques CS91051, 13781 Aubagne Cedex, France;1. Dodd-Walls Centre for Photonic and Quantum Technologies, Department of Chemistry, University of Otago, PO Box 56, Dunedin 9054, New Zealand;2. School of Pharmacy, University of Otago, PO Box 56, Dunedin 9054, New Zealand;3. Department of Anatomy, University of Otago, PO Box 56, Dunedin 9054, New Zealand |
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| Abstract: | In this work, the thermal behavior of the regularity modes in Raman spectra of polyethylene with different densities and random ethylene/1-hexene copolymers with varying content of comonomer are studied. We demonstrate especially that the vibrational modes at 1062 and 2850 cm↙1 are related to a critical sequence length of trans-conformers of 6⬜8 CH2 groups, while the modes at 1130, 1170, 1295, and 2883 cm↙1 indicate a critical sequence length of trans-conformers of 18 CH2 groups. Upon increasing the 1-hexene content in the ethylene/1-hexene copolymers, the evolution of the intensities of the Raman modes at 1062, 1130, 1170, 1295, and 1417 cm↙1, normalized to the intensity of the band at 2850 cm↙1, is similar to the evolution of the intensities of the same modes in the Raman spectra of low density polyethylene at increasing temperature. This observation however contrasts with that in the Raman spectra of polyethylenes with middle and high densities. We suppose that these results can be explained by similarities in the structure of non-crystalline areas of low density polyethylene and the ethylene/1-hexene copolymers, which contain significant amounts of short sequences of trans-conformers. |
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| Keywords: | Raman spectroscopy Regularity mode Random ethylene copolymer Polyethylene |
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