Cryopolymerization of N,N-dimethylacrylamide in moderately frozen formamide

Abstract

The free-radical polymerization of N,N-dimethylacrylamide initiated by the redox pair ammonium persulfate-N,N,N′,N′-tetramethylethylenediamine in moderately frozen and liquid formamides is studied at temperatures 10–30°C below or above the temperature of crystallization (2.9°C) of the pure solvent at various monomer concentrations in the initial solution. When polymerization is conducted at temperatures below the temperature of crystallization of formamide, the frozen systems, as is evident from their phase diagrams, include the crystallized main bulk of the solvent and the noncrystallizing monomer concentrated in the unfrozen liquid microphase where the reaction occurs. It is found that, in the case of this cryopolymerization variant, the temperature dependences of the yield of the polymer and its viscosity-average molecular mass show an extremum pattern and the positions of maximum points relative to the temperature scale depend on the initial monomer concentration. It is shown that the molecular masses of cryopolymerization products are much higher and their molecular-mass distribution is wider than that of poly(N,N-dimethylacrylamide) samples synthesized through solution polymerization (above the temperature of crystallization of formamide) at the same concentration of the monomer.