Nonergodic dynamics of a novel thermally sensitive hybrid gel

As the temperature decreases, the swelling of individual thermally sensitiv e spherical poly(N-isopropylacrylamide) microgels in a concentrated dispers ion can lead to a sol-gel transition, resulting in a hybrid bulk gel in whi ch 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 wer e studied by static and dynamic laser light scattering. Our results showed that the inhomogeneity should be characterized by the difference between th e ensemble average scattering intensity and the dynamic component of the ti me average scattering intensity. The inhomogeneity was strongly dependent o n the sol-gel transition rate and the gelling temperature. Our results have also revealed that the inhomogeneity can be completely suppressed if indiv idual swollen microgels are closely packed together, indicating that the st atic nonergodic behavior originates from large voids formed during the sol- gel transition.