NMR Relaxation, Polymer Dynamics, and Free Volume in Polyacrylate Solutions


The chain dynamics of polymer molecules in solution has been the subject of much scientific study. Polymer reorientation is important because the microscopic dynamics of polymer chains often dictates the physical properties of polymer solutions. NMR techniques can be used to probe the dynamics of polymers over many orders of magnitude in the frequency domain. In dilute solution, NMR results have provided insight into microscopic polymer dynamics. Carbon-13 and proton studies have shown that the relaxation times T//1 and T//2 are dominated by local segmental motions. These motions have been quantitatively described by invoking either jump or diffusion-like models, most of which have been reviewed by Heatley. Unfortunately, in more concentrated solutions, these models no longer fit NMR relaxation data in a physically meaningful manner. In this study the authors report **2H NMR relaxation results on solutions of polyacrylates in chloroform as a function of temperature and composition. The polyacrylates have been specifically deuterated at the backbone methine positions. Deuterium NMR is useful because the relaxation mechanism for a C-D species is well defined and simplified spectra (one resonance per spectrum) result. This is especially useful in concentrated solutions where the line widths can be very large and the overlap of resonances would normally occur in **1H or **1**3C NMR.



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