Colloidal microgels: synthesis, characterisation and applications

Four sets of NIPAM and non-NIPAM based colloidal microgels have been synthesized by a surfactant-free emulsion polymerisation (SFEP) technique, which are: (i) poly (NIPAM) based homo-polymer, (ii) poly (NIPAM) based co-polymer, (iii) hydrophobically modified homo-polymer and (iv) hydrophobically modified co-polymer microgels. Poly (NIPAM) based homo-polymer microgels have been studied with respect to their heteroaggregation/heteroflocculation behaviour with oppositely charged polystyrene latex (PS) particles. It has been shown that the particle size, concentration and temperature play an important role in the ionic interaction between oppositely charged microgel and PS latex particles. Some particulate dispersions have shown temperature-dependent reversible flocculation behaviour, which could be applicable in the water industry for the removal of colloidal impurity from water. A strong irreversible aggregation was also observed for some microgel-latex mixtures, which may find useful application in the field of crude oil recovery. Hydrophobically modified homo-polymer and co-polymer microgels have been prepared from a range of novel monomers. The monomers have been chosen with varying hydrophobic chain length in order to manipulate the swelling properties of the resultant particles in different solvents. The dispersibility behaviour of the novel and NIPAM-based microgels has also been studied in different solvents to find their utility in removing water from oil. Colloidal microgel particles have shown successful application in reducing the water content of biodiesel to an acceptable level. Karl Fischer titration results have shown that water level in biodiesel can be reduced below 500 ppm from 1800 ppm by using microgel as water absorbent. According to the EN14214 specification by European Committee 500 ppm is the maximum water level allowed in biodiesel to be useful in combustion engine