Nuclear Magnetic Resonance Spectra of Polymethyl Methacrylate in Solution. I. An Attempt to make Stereoregularity Measurements

The NMR spectra of polymethyl methacrylates prepared with various initiators have been examined. Three resonance peaks of α-methyl protons observed with an increasing magnetic field correspond to three species of the monomer units, i. e., I-, D- and S-units respectively. The proportion of each peak area may be used to characterize the stereoregularity of the polymer chain. A ternary diagram has been proposed to represent the stereochemical configuration of the polymers. Together with the average sequence lengths of the units, the possible polymerization mechanisms are considered. Free radical polymers of methyl methacrylate seem to be describable with a single parameter which depends only on the polymerization temperature. Some polymers prepared with anionic initiators show a stereoblock character. The polymerization mechanism has also been discussed in some idealized cases.