  Microgel particles composed of Interpenetrated Polymer Networks (IPN) of
poly(N-isopropylacrylamide) (PNIPAM) and poly(acrylic acid) (PAAc) dispersed in
water have been investigated through dynamic light scattering. The study of the
temperature, concentration and pH dependence of the relaxation time has
highlighted the existence of a thermoreversible transition corresponding to the
swollen-shrunken volume phase transition. The presence of PAAc introduces an
additional pH-sensitivity with respect to the temperature-sensitivity due to
PNIPAM and leads to interesting differences in the transition process at acid
and neutral pH.
