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95
Figure 38. Polymer chain and parameters defining the radius of gyration
R
G
is then defined as:
2
2
1
1
(
)
n
i i
i
G
n
i
i
m r
R
m
=
=
=
∑
∑
If m
1
= m
2
= …..= m then:
R
G
2
=
(
m
i
r
i
2
)
i
=
1
n
∑
m
i
i
=
1
n
∑
=
m r
i
2
i
=
1
n
∑
nm
=
r
i
2
i
=
1
n
∑
n
R
G
tells us indirectly whether the polymer is very expanded or very contracted.
Compare two polymers of the same molecular weight, but with different
extensions such as in the example below: