Hydrogels filled with thermosensitive microgel particles

Poly(acrylamide) (PAAm) hydrogels are prepared in the presence of temperature sensitive poly(N-isopropylacrylamide) (PNiPAM) microgels. The microgel particles are incorporated into the macroscopic hydrogel; however, the presence of the particles leads to a slower gelation process and the gel point is shifted to longer reaction times. Elastic properties of the hydrogel become temperature sensitive indicating a partial interpenetration of the PNiPAM microgels by the PAAm network. The hydrogel formation was performed at two temperatures where the PNiPAM microgels were either strongly or weakly swollen. Subsequent temperature changes lead to a change in microgel size and thereby influence the properties of the macroscopic gel. Static light scattering revealed enhanced long range heterogeneities that are temperature dependent in contrast to pure PAAm gels.