SEC With an On-Line Light-Scattering Detector

Furthermore, an on-line viscosity detector can be connected in tandem to the concentration detector (and the light-scattering detector). As we will learn in Section 3.3, the solution viscosity gives an important piece of information on the state of polymer molecules in solution. 

Problem 2.33 An excluded-volume chain of N monomers of size b has a dimension of Rp = bN . Grouping monomers into one big monomef makes a chain of N/rii big monomers with excluded volume. Within each big monomer, the chain is stiU an excluded-volume chain of monomer size b. Show that this coarse-grained chain has the same dimension as that of the original chain. 

Solution 233 The size of the big monomer is bn/. Therefore, the dimension of the coarse-grained chain is brii)(N/n = bN, identical to Rp of the original chain. The choice of is arbitrary. 

Problem 2.34 Hory s method, we learned in Section 1.4 to find the dimension of the real chain, can be extended to the confined real chain. Find the relationship between the dimension of the chain along the sUt wall or the tube wall, R, and the degree of polymerization N for the confinement by (1) a sUt of width d and (2) a tube of diameter d. 

Solution 2.34 (1) The volume for a polymer chain confined to the slit is R/d. Then, the monomer density is N/ R d). The interaction term in Eq. 1.63 is now The free energy of the chain with a dimension of / n is 

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