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EXCLUDED VOLUME



1


Excluded volume applies to the volumes of space that a growing polymer chain cannot move into because that space is already occupied by previously polymerized chain.

In the picture above, monomers are approximated by spheres with radius R. Each sphere is surrounded by a sphere of light with a radius 2R. This sphere of light represents the volume of space excluded from an approaching sphere, such that the center of the approaching sphere cannot move within this volume. When the center of an approaching sphere touches the sphere of light, the edge of the approaching sphere is touching the edge of the other sphere.
    Visually, we think of beads as spheres, but when it comes to the mathematics, each sphere may be treated as an infinitismally small point at the center of the sphere, thus mathematically the boundary is drawn to define where the center of an approaching sphere can and cannot go.




A "self avoiding random walk" takes into account excluded volume, in contrast to a random walk where the polymer can polymerize through previously polymerized polymer chain.

The radius of gyration increases when the excluded volume effect is included in a polymer model.

The IUPAC definition for excluded volume focuses on the idea that the volume occupied by one macromolecule is not available for occupation by another macromolecule.