Morphological study of graft copolymers of maize starch with Acrylamide and Methacrylamide

The graft copolymers of granular maize starch with two vinyl monomers namely- acrylamide and methacrylamide were synthesized using ceric ammonium nitrate. Gravimetric estimation was used to calculate percent grafting. While acid hydrolysis and infra-red spectroscopy was used to confirm the grafting. Scanning Electron Microscopy (SEM) is the right technique to study the surface morphology of starch spherulites as their size ranges between 3 and 100 µm. The study of SEM photographs of pure granular maize starch granules and starch-graft-acrylamide and starch-graft-methacrylamide was carried out at different magnification. It was observed that surface morphology of starch changes on grafting with these monomers and is easily distinguishable from that of pure starch. In case of starch-graft-acrylamide, although the granules remained almost separate from each other, their shape changed from spherical to polyhedric. The SEM photographs of starch-graft-methacrylamide, revealed that the grafted polymer formed a thin layer on the surface of starch granules and most of the granules were joined through the surface layer of grafted polymer. SEM studies can thus be used not only to confirm grafting onto starch spherulites but if method is properly standardized can be used to characterize the graft polymer.