Nuclear magnetic resonance free radical polymerization

The proportion of head-to-head structures can be considerable in some cases. For example, in free-radical-polymerized poly(vinylidene fluoride), -fOH2—CF2 fi, there are about 10-12% of such links according to nuclear magnetic resonance measurements ( H and F). The proportion is as high as 6-10% in poly(vinyl fluoride). Admittedly, these physical methods... 

In the free radical polymerization proeess, conducted usually at elevated temperatures, these effects are insignificant and the reaction usually leads to the formation of atactic polymer only. However, in some cases, like, for example, in free radical polymerization of methyl methacrylate at temperature below 0°C one obtains a crystalline polymer with syndiotactic structure, as it was proven by the high resolution nuclear magnetic resonance spectroscopy. These results confirm the rule that according to which the degree of stereoregularity decreases with increasing temperature. 

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