ISSN:
1572-8870
Keywords:
Poly(ethyl-n-butylsilylene)
;
structure
;
thermal properties
;
flow
;
molecular weight
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Abstract Poly(ethyl-n-butylsilylene) (PEBS) was synthesized by sodium coupling of ethyl-n-butyldichorosilane and separated into fractions with differing molecular weights,M w=1.4×106 and 2.0×104. Both fractions were studied by differential scanning calorimetry and by X-ray diffraction, UV spectroscopy, polarizing optical microscopy, and capillary rheometry, all as a function of temperature. Both samples adopt a hexagonal columnar liquid crystalline structure at room temperature and below. They undergo a weak endothermic transition at −20°C and a first-order phase transition to a nematic liquid crystalline form at 90°C for the low and 170°C for the highM w fraction. Melting to an isotropic liquid takes place at 106°C for the low and 185°C for the highM w polymer. Both samples undergo two successive thermochromic transitions in the UV, one near the first-order exothermic transition and one near the −20°C transition; the reasons underlying these thermochromic transitions are discussed. Flow properties of PEBS were investigated as a function of molecular weight.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00684027
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