a) b - École Polytechnique de Montréal

Shapes and sizes of polymer molecules are controlled by the nature of the covalent bonds that
bind the atoms of the molecule together. Generally, polymer molecules in a particular kind of
solution or in a melt state have a coil shape which is called a random coil. Solvent affinity also
affects the conformation of polymers associated with polymer architecture. Therefore, a random
conformation is usually found for an uncharged linear polymer chain in solution. In the case of
polyelectrolytes, charge also has a significant influence, as charged linear polyelectrolyte chains
repel each other due to coulomb repulsion, which causes the chain to adopt a more expanded
rigid-rod-like conformation. Persistence length is defined as a characterization factor for stiffness
on macromolecule chains. It is the length over which the normalized bond vectors at different
locations on the chain are correlated. It can also be described as an estimate for the typical radius
of curvature of chains.
a)
b)
c)
d)
Figure 2-35. Schematic view of the four scaling ranges in the Gaussian-persistent regime(Netz
& Andelman, 2003)
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