Poly(N-Isopropylacrylamide) Microgel Synthesised by Emulsion Polymerization

Smart polymers have been one of the most popularly studied materials owing to their capability to alter physio-chemical behaviour upon exposure to specific external stimuli. The biocompatible thermally responsive poly (N-isopropylacrylamide), PNIPAm shows reversible transition between hydrophilic-hydrophobic characteristics at the vicinity of human physiological temperature has great potential to propel the development of smart tissue engineering scaffold and drug delivery. However, the limited availability and its high cost have dampened the extent of research on this polymer. To address these challenges, the current work demonstrates an economical lab-scale polymerization of crosslinked PNIPAm and the optimised parameters to produce mono-dispersed polymer hydrogel particles were investigated. Characterisation of the synthesized PNIPAm polymer revealed particle size polydispersity index of 0.215, indicative of distribution within the mono-dispersed range, with average hydrodynamic diameter of 346.3 nm. Zeta-potential of the synthesized PNIPAm was found to be -20.6 mV, suggesting an incipient instability in terms of colloidal coagulation. Viscosity of the synthesized PNIPAm (4 wt% concentration in methanol) was 28.6 cP. Thermal gravimetric analysis (TGA) indicated the thermal degradation of main chain PNIPAm fell in the range of 340 to 480°C.