Synthesis of graphene oxide doped poly(2-acrylamido-2-methyl propane sulfonic acid) [GO@p(AMPS)] composite hydrogel with pseudo-plastic thixotropic behavior

The aim of the present study was to investigate rheology and rheological models to elucidate the structural characteristics of graphene oxide doped poly(2-acryloamido-2-methyl propyl sulfonic acid) [GO@p(AMPS)] composite hydrogel. The graphene oxide (GO) was synthesized via modified Hammers method and characterized by X-ray diffraction. This GO-hydrogels were synthesized in GO dispersed medium by adding AMPS as a monomer via free radical addition polymerization. The material was characterized by SEM, FT-IR spectroscopy and Rheometry. The flow curve and flow sweep study of the GO@p(AMPS) hydrogel indicates that the material has pseudo-plastic thixotropic behavior. The finding from the study of storage (G′) and loss (G″) moduli shows that the GO@p(AMPS) behave elastically, semisolid and pseudo-plastic in their nature. The yield stress data indicate that the materials need an external force (activation energy) to break the internal network of the gel. Creep-recovery tests were applied which show that the gels have the ability to recover the network after removal of the external stress. The flow characteristics of the gel were studied by various rheological models, the data were best fitted in the Bingham modified model. Further the damping factor (tan δ) is near to 0.3, which shows the improvement of the damping of the materials due to the interlocking and penetration of GO particles within the gel. Thus, the rheological analysis show that these materials can be applied for complex cosmetics, controlled drug loading and release due to the presence of GO as a drugs binding effector in GO@p(AMPS) composites.