SMALL-ANGLE NEUTRON-SCATTERING STUDY ON POLY(N-ISOPROPYL-ACRYLAMIDE-CO-ACRYLIC ACID) COPOLYMER SOLUTIONS

The structure factor (scattered intensity), I(q), for weakly charged polymer solutions of a poly(N-isopropyl acrylamide-co-acrylic acid) copolymer (NIPA/AAc) was obtained by means of small-angle neutron scattering (SANS) as a function of temperature, where q is the magnitude of the scattering vector. It was found that I(q) was well described with a Lorentz-type scattered intensity function when the temperature was lower than the so-called THETA temperature, which is about 34.6-degrees-C. Above this temperature, I(q) started to have a peak around q = 0.02 angstrom-1, which increased with temperature. In addition, an upturn in I(q) appeared by approaching q = 0, indicating a macroscopic inhomogeneity. The structure factor was analyzed on the basis of the theory of Borue and Erukhimovich for polyelectrolytes in a poor solvent [Macromolecules, 1988, 21, 32401.