Paper Title:
Phase Transitions in Polymers Containing Long Self-Assembled CH2 Sequences in the Side Chain: A Positron Lifetime Study
  Abstract

Positron lifetime annihilation spectroscopy (PALS) was used to study the temperature- dependence of sub-nanometer size local free volumes in two atactic poly(n-octadecyl methacrylate)s (PODMA) with different molecular weight. These materials exhibit short range layered structure with a self-assembly and crystallization of side chains. From the ortho-positronium (o-Ps) lifetime the size of free volume holes and its distribution are calculated. At a temperature Tm=311 ± 5 K, the mean hole volume shows an abrupt and strong increase from 0.15 nm3 to 0.2 nm3, which comes from the melting of side-chains. The reverse effect, attributed to side chain crystallization, was observed during cooling the samples at slightly lower temperatures. The lifetime result of PODMA is compared with semifluorinated polyesters in which the side chain has an oxydecylperfluorodecyl structure (-O-(CH2)10-(CF2)9-CF3). Long chain polymers without side-chains such as polyethylene and short side-chain poly(n-alkyl methacrylate)s: poly(methyl methacrylate) (PMMA) and poly(n-hexyl methacrylate) (PHMA) are also compared with these polymers.

  Info
Periodical
Edited by
Radosław Zaleski
Pages
71-74
DOI
10.4028/www.scientific.net/MSF.666.71
Citation
Y. Yu, G. Dlubek, R. Krause-Rehberg, M. Beiner, E. Hempel, "Phase Transitions in Polymers Containing Long Self-Assembled CH2 Sequences in the Side Chain: A Positron Lifetime Study", Materials Science Forum, Vol. 666, pp. 71-74, 2011
Online since
December 2010
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