Behavior of hyperbranched polymers in solutions |
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Authors: | A P Filippov E V Belyaeva E B Tarabukina A I Amirova |
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Affiliation: | 1.Institute of Macromolecular Compounds,Russian Academy of Sciences,St. Petersburg,Russia |
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Abstract: | Hyperbranched polycarbosilanes are investigated by the methods of molecular hydrodynamics and optics. Dependences of the hydrodynamic
and conformational properties of these polymers on their molecular mass, the length of linear chains between branching points,
and the chemical structure of end groups are analyzed. The hydrodynamic behavior of hyperbranched polycarbosilanes is explained
by the fact that the dimensions of their macromolecules are compact and their shape is close to spherical. The convolution
of chains between branching points becomes more pronounced with an increase in their length and a decrease in the molecular
mass of the polymer. When end fluorinated groups are incorporated into the hyperbranched polycarbosilane, in thermodynamically
good solvents and θ solvents, hydrodynamic characteristics change apparently owing to a change in the density of macromolecules
in solution. In a poor solvent, the compaction of fluorinated macromolecules and a reduction in their shape asymmetry are
observed. At a fixed branching degree, the hydrodynamic properties of hyperbranched polymers depend on the structural regularity
of their macromolecules: In terms of hydrodynamic properties, the hyperbranched polycarbosilane with a degree of branching
of 1 and a random distribution of branching points within the volume of a macro-molecule is appreciably different from a dendrimer
of the same chemical nature and is close to polycarbosilanes with a degree of branching of 0.5. |
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