Anionic synthesis of narrow molecular weight distribution water-soluble poly(N,N-dimethylacrylamide) and poly(N-acryloyl-N'-methylpiperazine)

Water-soluble poly(N,N-dimethylacrylamide) (PDMA) and poly(N-acryloyl-N'-methyl-piperazine (PAMP) were prepared in tetrahydrofuran at -78 degrees C by anionic polymerization in the presence of monofunctional initiators such as (triphenylmethyl)lithium, or -cesium or the difunctional initiators (1,1,4,4-tetraphenylbutyl)lithium, -potassium, or -cesium or cesium naphthalenide. Polymerizations initiated especially in the presence of cesium as counterion proceeded in a homogeneous manner and gave polymers having controlled molecular weights and narrow molecular weight distributions in quantitative yields. However, the polymerization results in polymers with a lower molecular weight and a broad molecular weight distribution at higher reaction temperatures. Size exclusion chromatography, H-1 NMR spectroscopy, and intrinsic viscosity measurements support the clean anionic polymerization of DMA with few side reactions at -78 degrees C. Attempted anionic polymerizations of methacrylamide monomers such as N,N-dimethylmethacrylamide and N-methacryloyl-N'-methylpiperazine are described as well. NMR spectroscopy, differential scanning calorimetry, and solubilities of the resulting polymers revealed the influence of the initiator counterions on the polymer tacticity.