Dynamic mechanical properties of extruded rods of poly(dimethylsilylene) and polysilane copolymers having methyl and ethyl substituents

Citation
A. Kaito et al., Dynamic mechanical properties of extruded rods of poly(dimethylsilylene) and polysilane copolymers having methyl and ethyl substituents, MACRO MAT E, 286(6), 2001, pp. 369-376
Citations number
19
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Organic Chemistry/Polymer Science
Journal title
MACROMOLECULAR MATERIALS AND ENGINEERING
ISSN journal
1438-7492 → ACNP
Volume
286
Issue
6
Year of publication
2001
Pages
369 - 376
Database
ISI
SICI code
1438-7492(20010629)286:6<369:DMPOER>2.0.ZU;2-C
Abstract
The oriented rods of poly(dimethylsilylene) (PDMS), poly(diethylsilylene-co -methylethylsilylene) (PMMME) and poly-(diethylsilylene-co-methylethylsilyl ene) (PEEME) were prepared by extruding the polymers through a circular tub e die in the temperature range where the hexagonal mesophase forms. In gene ral PDMS cannot be processed into materials below its decomposition tempera ture, but is was found that PDMS could be compression molded ata 250 degree sC under nitrogen atmosphere prior to the extrusion. The extruded polysilan es were characterized in detail by dynamic viscoelasticity and wide-angle X -ray diffraction in order to clarify the structure-property relationship. t he temperature dependence of wide-angle x-ray diffraction showed that the c rystalline phases of PDMS, PMMME, and PEEME were transformed into the hexag onal mesophase at elevated temperatures. The dynamic storage modulus of PDM S amounts to 7.6 GPa at room temperature and 11.2 GPa at liquid nitrogen te mperature. The dynamic storage modulus increases with extrusion ratio is we ll correlated with the change of the crystal orientation function. The dyna mic storage moduli of the extruded polysilanes were lowered with the rise i n temperature owing to the structure relaxation processes, which lie in the lower temperature range. The decrease of modulus with temperature was more marked in PEEME than in PDMS, suggesting that the molecular motion of the ethyl substituents lowered the modulus at room temperature.