Unusual influences of temperature and medium on the tacticity of radically polymerised poly(n-vinyl imidazole)

The tacticities of radical poly(N-vinyl imidazole)s prepared in several organic solvents, in water and at various values of pH and temperature have been investigated by ¹H and ¹³C-NMR. It seems most likely that high temperatures favour racemic placements over meso placements but that, at low pH, meso placements are favoured. Thus the changes in polymerisation rate with pH noted by others for this system are accompanied by changes in the stereochemistry of the resulting polymer.