STRUCTURAL TRANSFORMATIONS IN POLY(DI-N-ALKYLSILOXANE)S WITH ALKYL SIDE-GROUPS CONTAINING 7 TO 10 CARBON-ATOMS

Citation
A. Turetskii et al., STRUCTURAL TRANSFORMATIONS IN POLY(DI-N-ALKYLSILOXANE)S WITH ALKYL SIDE-GROUPS CONTAINING 7 TO 10 CARBON-ATOMS, Polymer, 36(6), 1995, pp. 1303-1308
Citations number
26
Categorie Soggetti
Polymer Sciences
Journal title
ISSN journal
00323861
Volume
36
Issue
6
Year of publication
1995
Pages
1303 - 1308
Database
ISI
SICI code
0032-3861(1995)36:6<1303:STIPWA>2.0.ZU;2-O
Abstract
Temperature dependent X-ray diffraction studies of poly(di-n-alkylsilo xane)s substituted with side chains containing 7 to 10 carbon atoms ha ve been carried out in order to elucidate the crystalline structure of these materials. In contrast to their lower substituted homologues, n o evidence for the presence of a hexagonal columnar mesophase could be found for the investigated materials. At low temperatures, far below the melting temperature, the polysiloxane backbones are assumed to pac k in an orthorhombic lattice, with the n-alkyl side chains in a planar all-trans conformation and oriented perpendicularly to the backbone. The paraffinic n-alkyl side chains were found to crystallize in an ort horhombic lattice. The thermal behaviour of the investigated materials has been observed to show an odd-even effect. Whereas poly(di-n-hepty lsiloxane) and poly(di-n-nonylsiloxane) were found to melt in a single step, an intermediate state of order was observed for poly(di-n-octyl siloxane) and poly(di-n-decylsiloxane) upon heating from the crystalli ne to the isotropic state. For this intermediate state, a pseudohexago nal packing of the n-alkyl side chains is proposed.