Dilute isotropic solutions polymerization

There is no definite evidence of synthetic supramolecular polymers able to produce the extremely large DP achieved in the helical polymerization of biological systems. The polymer in Fig. 2B has been reported to display a triple helical structure in the solid state [9]. However, occurrence of large DP in isotropic solution was not reported. The H-bonded assembly involving pimelic acid and bis-2-aminopyridine has been suggested to exhibit helical structure in both sohd state and diluted solutions ([137] cf. also this volume, Chapter 4). Guidehnes for future attempts to synthesize helical supramolecular polymers stable even in... 

The overall rotational mobility of the polymer, rather than segmental motions, is primarily responsible for the motional averaging of the dipolar and chemical-shift interactions to their isotropic values. The viscosity can be decreased and the motion can be increased by making more dilute polymer solutions and by increasing the measurement temperature. In this manner, narrower lines for high-resolution speetra can be obtained for polymers in solution. Special techniques are required to obtain high-resolution spectra of polymeric solids [21,22]. 

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