Polymers as Chains of Beads and Springs

A more realistic representation of polymer chains is the Rouse model [59], which considers a polymer molecule to be a linear chain of N free-draining beads interconnected by springs (each of time constant Xu = il4H), and predicts Eq. (16) to apply. 

This implies that [ /] has a linear dependence on molecular weight. This is not consistent with the experimental observations [Eq. (12)]. When hydrodynamic interaction and excluded volume effects between chain segments are considered, the corresponding Zimm model [60] correctly predicts the dependence [Eq. (17)]. 

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