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050506 Quiz 6 Polymer Properties

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050506 Quiz 6 Polymer Properties

Renormalization of disordered structures has been used as a tool to describe the structural adaptation of thermally equilibrated macromolecules. For macromolecules renormalization involves the concept of a "blob". We discussed two kinds of blobs in class, the thermal blob (or thermic blob) and the concentration blob.

a) How is the thermal blob used to renormalize a polymer chain? Give the conditions (you may need a plot of Rg vs T); an equation for RF (in terms of N, b, and ); an equation for the blob size, and sketch in a plot of log I versus log q the behavior of a SAW chain, a Gaussian Chain and a chain displaying thermal blobs. Be sure to indicate intransigent parts of the curves.

b) Explain the analogy between Debye screening of static charges and screening in semi-dilute polymer solutions. What are the main differences?

c) How is the concentration blob used to renormalize a polymer chain? Give the conditions; an equation for RF; an equation for the blob size; and sketch in a plot of log I versus log q the behavior of a SAW chain, a Gaussian Chain and a chain displaying concentration blobs. Be sure to indicate intransigent parts of the curves.

d) Could blob theory be used to understand ceramic aggregate structures? Explain why or why not. Try to be as specific as you can and give an example sketch of the structure.

e) Could the persistence length be viewed as a blob? Explain your answer.

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