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Structure and crystallization of n-C21H44, n-C36H74 and low molecular weight polyethylene glasses

Strauss, Herbert L.
Snyder, R.G.
Published in Macromolecules. 1987, vol. 20, no. 11, p. 2810-2819
Abstract Glassy films of n-CzlH,, n-C36H74a, nd low molecular weight polyethylene were prepared by vacuum sublimation onto a CsI window held at 7 K and were studied by infrared spectroscopy. The conformational disorder achieved for the glass was comparable to that of the liquid near the sublimation temperature. The chain-organizing processes were monitored for Czl and polyethylene as the sample was warmed to 300 K. A number of separate steps are involved. Each step occurs over a more or less broad temperature region, and sometimes the steps overlap. In the case of CZ1, the first step involves a conformational ordering of the chains to their extended all-trans form. The extended chains initially pack in a monoclinic subcell, but they are not in longitudinal register; that is, the end methyl groups do not lie in parallel planes. At a higher temperature, the monoclinic subcell is converted to an orthorhombic subcell, but the chains are still not in register. In the last annealing step, which occurs over a narrow temperature range, the chains come into register so that the Czl finally assumes its stable orthorhombic crystal structure. The annealing of the polyethylene glass proceeds in exactly the same way except that there is no chain-registering step. In general, the transition temperatures are higher and the temperature range over which the transitions occur is broader for the polyethylene sample.
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Research group Groupe Bill
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HAGEMANN, Hans-Rudolf, STRAUSS, Herbert L., SNYDER, R.G. Structure and crystallization of n-C21H44, n-C36H74 and low molecular weight polyethylene glasses. In: Macromolecules, 1987, vol. 20, n° 11, p. 2810-2819. https://archive-ouverte.unige.ch/unige:3090

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Deposited on : 2009-09-21

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