Radical polymerization reactions Nuclear magnetic resonance

The inhibiting effect of radical acceptors, however, suggests that polymerization proceeds by a radical mechanism. The yield of polymer from such reactions depends on the tendency of the different monomers to be polymerized by ionic and radical catalysts. The reactivity ratio on grinding for styrene plus methyl methacrylate is similar to that for peroxy-initiated polymerization. Nuclear magnetic resonance data, however, show a different stereochemical configuration for the copolymers [200]. 

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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