7. (a) Explain what is meant by the radius of gyration of a polymer. How is it related to the end-to-end distance for a

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7 A Explain What Is Meant By The Radius Of Gyration Of A Polymer How Is It Related To The End To End Distance For A 1 (131.4 KiB) Viewed 80 times

7. (a) Explain what is meant by the radius of gyration of a polymer. How is it related to the end-to-end distance for a single chain polymer and what is its significance? 2 When «R,<<1 the intensity, I, of neutron scattering from a polymer molecule obeys the law I = Lexp(-x2 R, 2/3) where I, is the incident intensity, z is related to the angle of scattering, and R is the radius of gyration. Two samples of amorphous polystyrene, A and B, each containing a small fraction of deuterium labelled polymer, gave the scattering data in the table below. x/nm-1 0.1 0.2 20.3 0.4 IÆ/arbitrary units 0.776 0.365 0.103 0.018 Ip/arbitrary units 0.474 0.023 1.48x10-4 Determine the radii of gyration of each of the polymers. The molecular weights (Mn) of the two samples are 100k (sample A) and 400k (sample B). Comment on the relation between the two values you obtain. R = 8.7 nm (A) and 17.4 nm (B)