Comparison in fractal dimension between those obtained from structure factor and viscoelasticity of gel networks of 1,3:2,4-bis-O-(p-methylbenzylidene)-D-sorbitol in polystyrene melt at gel point.
We investigated time evolution of shear moduli in the physical gelation process of 1,3:2,4-bis-O-(p-methylbenzylidene)-D-sorbitol in polystyrene melt. At the gel point, storage and loss shear moduli, G' and G", were described by the power law of frequency omega, G' approximately G" approximately omegan, with the critical exponent n being nearly equal to 2/3, in agreement with the value predicted by the percolation theory. We also investigated the structure factor over two decades in length scale at gel point by using ultra-small-angle X-ray scattering, and small-angle X-ray scattering. We found the power-law behavior in low-q region, indicating that the gel network forms the self-similar structure with mass-fractal dimension. Comparison between the exponent of mass-fractal dimension from structure factor and that from viscoelasticity indicates that hydrodynamic interactions are completely screened out and the excluded volume effects are dominant in the gel. The gel strength was found to increase with the decrease in the lower limit length scale of fractality.
Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University, Nishikyo-ku, 615-8510, Japan.
Mikihito
M
Takenaka
Toshiaki
T
Kobayashi
Kenji
K
Saijo
Hirokazu
H
Tanaka
Naoki
N
Iwase
Takeji
T
Hashimoto
Masaoki
M
Takahashi
D001597:Benzylidene Compounds / Q000737:chemistry*; D004548:Elasticity; D017709:Fractals; D005782:Gels; D011137:Polystyrenes / Q000737:chemistry*; D012542:Scattering, Radiation; D013012:Sorbitol / Q000031:analogs & derivatives* / Q000737:chemistry*; D014783:Viscosity; D014965:X-Rays
D001597:Benzylidene Compounds; D005782:Gels; D011137:Polystyrenes; D013012:Sorbitol