Synthesis, Characterization and Water Swelling Properties of Borassus Aethiopum Starch-G Polyacrylamide Hydrogels

Abstract

Starch was extracted from Borassus aethiopum tuber using blending, filtration 
decantation methods. The starch-g-polyacrylamide was prepared by graft 
copolymerization between the Borassus aethiopum starch and acrylamide via 
solution polymerization using potassium per sulphate (KPS), as initiator and N1, N1
Methylenebisacrylamide (crosslinker) respectively. The maximum water swelling 
percentage of the starch-g-polyacrylamide obtained at 0.2 g of initiator content was 
found to be 470 % with starch to the monomer ratio of 1:1. The functional group of 
the Borassus aethiopum starch, and the synthesized hydrogel were characterized 
by fourier transform infrared (FTIR) spectroscopy (model Cary 630 MY13270004 
G8043-64002). The IR spectra of Borassus aethiopum starch obtained depict the 
presence of O-H stretching absorption band in the region of 3286 cm-1 (broad).  The 
C-H bond stretching at 2933 cm-1 (medium) and absorption bands of 1153, 1082 
and 996 cm-1 (s) for the C-O-C bond stretching. While spectra of starch-g
polyacrylamide display N–H stretching in the region 3500-3200 cm-1, 1655, and 
1607 cm-1 indicated the presece of C=O stretching and N–H bending of the amide 
bands, respectively. This revealed the presence of -CONH2 functional group of the 
acrylamide before and after purification which shows all the absorption peaks of 
Borassus aethiopum starch. The raw starch and synthesized hydrogels were 
characterized using SEM and DSC. The SEM micrograph of the starch sample 
showed irregular shapes and varied particle sizes with white smooth surfaces. The 
SEM micrograph of the starch-g-polyacrylamide shows a very smooth surface with 
three dimensional networks on the SEM micrograph. The thermal stability of the 
Borassus aethiopum starch and starch-g-polyacrylamide hydrogels was also 
determined and found to be 68 oC and 75 oC respectively. This shows improvement 
of the thermal stability of the synthesized hydrogel. Therefore, purified Borassus 
aethiopum starch could be used in the synthesis of hydrogel