Macromolecules, Vol.34, No.22, 7804-7808, 2001
Nonergodic dynamics of a novel thermally sensitive hybrid gel
As the temperature decreases, the swelling of individual thermally sensitive spherical poly(N-isopropylacrylamide) microgels in a concentrated dispersion can lead to a sol-gel transition, resulting in a hybrid bulk gel in which individual microgels were physically jam-packed into a three-dimensional network without involving electrostatic interaction, resembling the glass transition of small molecules. The dynamics of such a formed hybrid gel were studied by static and dynamic laser light scattering. Our results showed that the inhomogeneity should be characterized by the difference between the ensemble average scattering intensity and the dynamic component of the time average scattering intensity. The inhomogeneity was strongly dependent on the sol-gel transition rate and the gelling temperature. Our results have also revealed that the inhomogeneity can be completely suppressed if individual swollen microgels are closely packed together, indicating that the static nonergodic behavior originates from large voids formed during the sol-gel transition.