Abstract
The precision and the accuracy in determining the tacticity of poly (methyl metacrylate) (PMMA) by NMR spectroscopy have been investigated in detail. Using a number of 60 and 100MHz spectrometers the spectra of PMMA obtained in toluene at 60°C by AIBN catalyst were measured at various r. f. field strengths in CHCl3 (or CDCl3) and in CH3NO2 (or CD3NO2) at 60 and 100°C, respectively, and the triad tacticities were determined. The tacticities of the mixtures of isotactic and syndiotactic polymers and of syndiotactic and atactic polymers were also determined and the results were compared with the tacticities calculated from those of each component polymers and the compositions of the mixtures in order to evaluate the accuracy of the measurements. From these results it was concluded that the precision and the accuracy of the measurements were within a few per cent and that even in a radical polymerization the ratio of 4IS/HH2 did not become unity under a certain condition suggesting that the stereoregulating propagation step was not strictly Bernoullian.
