Light scattering and small angle neutron
scattering (SANS) on polymers.
In light scattering experiments we probe in a q-range
of approximately 0.0005  q(Å-1)  0.005, whereas
with SANS we monitor structural changes on roughly
0.005  q(Å-1)  0.8. This shows that intensity light
scattering of polymer systems gives information on a
global dimension, while SANS probes the structure
on a more local scale.
Guinier approximation: (qRg  1):
I(q )  A exp(
q 2 R g2
3
)
The radius of gyration can be determined.
a
Observation of a strong upturn of the scattered
intensity at low q values suggests large association
complexes. The upturn at low q can be described by a
power law with an exponent of -4, characteristic of
Porod scattering.
At large q (qL>>1; L is a characteristic length; Rg or
the screening length  in semidilute solutions) a
power law is observed I(q)  q-df.
3
10
2
10
o
d-
slo
pe
1
=
-4
.0
-1
I(q) (cm )
10
25 C
o
35 C
o
45 C
o
55 C
Po
ro
0
10
-1
10
-2
10
EHEC/D2O
-3
10
-3
-2
6x10
10
-1
10
-1
q (Å )
b
-1
4x10