Hydrophobic interactions in the radical polymerization of acrylamide derivatives

The radical polymerization of acrylamide, N-butylacrylamide (BAA) and N-octylacrylamide (OAA) in mixtures of water and tetrahydrofuran (THF) of various compositions is investigated. The rate of acrylamide polymerization sharply decreases when THF is added to a water solution of monomer. In the polymerization of BAA and OAA the strong dependence of the total rate of reaction on the composition of the mixed solvent is observed. In the case of BAA the reaction proceeds with maximal rate at a content of about 35 mol% of water in the mixed solvents. In the polymerization of OAA, the maximal reaction rate is observed at contents 10–15 mol% of water in the mixed solvents. The addition of sodium bromide is accompanied by an increase of the polymerization rate of BAA, and displacement of the maximum towards smaller contents of water. On the other hand, in the presence of urea, the polymerization proceeds with maximal velocity at higher contents of water in mixed solvents. The obtained results are explained in view of the influence of hydrophobic interactions arising in the reaction system in the presence of water.