ISSN:
1435-1536
Keywords:
Dielectric measurements
;
label
;
polyisoprene
;
ball-like molecules
;
glass process
;
local process
;
voids
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
,
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Abstract Ball-like molecules with strong dipoles (labels) were mixed with synthetic polyisoprene (IR305) in low concentrations (〈1%) and measured dielectrically in the frequency range 10−2–107 Hz and the temperature range −70–0°C (glass relaxation region). Calorimetric measurements showed that this type of label has a plasticizing effect on the polymeric matrix. The dielectric measurements showed that these ball-like molecules relax through cooperative rotations with the polymeric segments and at the same relaxation frequency. In addition, the label molecules showed a high-frequency local relaxation process. The relaxation strength ratio of the local process (X local) to the total relaxation strength of the label was found to be dependent on the volume as well as on the shape of the label. A comparison between the relaxation behaviors of the ball-and rod-like molecules, having the same volume, showed that the length of the label is also an important parameter for the determination of the local contribution as well as of the cooperative relaxation mechanism of the label. The label relaxation process is discussed in relation to the molecular packing of the host polymer.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00653306
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