Spatial inhomogeneities of poly(N-isopropylacrylamide-co-acrylic acid)
(NIPA/AAc) gels were investigated by dynamic light scattering as a fu
nction of AAc comonomer concentration and temperature. The results sho
wed the following: (1) The ensemble average scattered intensity, [I](E
), decreased with increasing AAc comonomer concentration and increased
with temperature. (2) Dynamic fluctuations increased with temperature
and diverged at the transition temperature, T-c. (3) Above the Theta
temperature of NIPA homopolymer in an aqueous solution, the intensity-
intensity time correlation function did not fit a single-exponential f
unction, but fit a double exponential or a stretched exponential, indi
cating a heterogeneous structure, i.e., polymer-rich and polymer-poor
phases at temperatures above Theta.