Acrylamide-b-N-isopropylacrylamide block copolymers: Synthesis by atomic transfer radical polymerization in water and the effect of the hydrophilic-hydrophobic ratio on the solution properties

A series of block copolymers of acrylamide and N-isopropylacrylamide (NIPAM) characterized by different ratios between the length of the two blocks have been prepared through atomic transfer radical polymerization in water at room temperature. The solution properties of the block copolymers were correlated to their chemical structure. The effect of the hydrophilic/hydrophobic balance on the critical micelle concentration (CMC) was investigated. The CMC increases at higher values for the solubility parameter, thus indicating a clear relationship between these two variables. In addition, the solution rheology (in water) of the block copolymers was studied to identify the effect of the chemical structure on the thermo-responsiveness of the solutions. An increase in the length of the PNIPAM block leads to a more pronounced increase in the solution viscosity. This is discussed in the general frame of hydrophobic interactions strength. The prepared polymers are in principle suitable for applications in many fields, particularly in enhanced oil recovery. (C) 2013 Wiley Periodicals, Inc.