Summary of polymer solutions

The phase diagram of polymer solutions is shown in Fig. 5.1, assuming the usual case of5 0in Eq. (4.31) (with x — BjT i decreasing function of temperature . In the poor solvent half of the diagram (at temperatures below 6) the binodal separates the two-phase region from the two singlephase regions. 

At sufficiently high temperatures, the solvent is gbbd, with three regimes. There is a dilute good solvent regime at concentrations 

Concentrated solutions occur above the concentration (j) at which the thermal blob size and the correlation length coincide (at — 

Chains have nearly ideal statistics on all length scales in concentrated 

Semidilute and concentrated solutions are characterized by a correlation length C the scale at which a given chain starts to find out about other chains. This correlation length is 

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There are literally thousands of published 2D-NMR pulse sequences. Many of these provide slightly different ways of getting the same stmcture information. There are a few that are extremely useful and that are used quite frequently these are summarized in Table 4. A description of the spedfic pulse sequences used to collect even this limited number of experiments would require far more space than is available for this brief summary of polymer solution NMR. For details, the reader can refer to References 2, 5, and 16-18. Discussions here will be limited to a few key features necessary to learn the relative difficulty assodated with performing each experiment, and the nature of the structure information obtained from the spectmm produced by each experiment. 

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