Graft copolymerization of polyDADMAC to cassava starch: Evaluation of process variables via central composite design

Grafting of polydiallyldimethylammonium chloride (polyDADMAC) to cassava starch was prepared using potassium persulfate (KPS) as a free radical initiator. Response surface methodology (RSM) comprising a three-level and four-variable central composite designs were implemented for variable evaluation and optimization. These variables include the mole ratio of diallyldimethylammonium chloride (DADMAC) to starch (anhydroglucose unit (AGU)), reaction temperature (°C), initiator concentration (mol/L), and reaction time (t). Grafting percentage was considered as a response from the variable interaction. The optimum condition derived were 1.96 [mole ratio of DADMAC to starch (AGU)], 40 °C (reaction temperature) 0.09 mol/L (initiator concentration) and 4.99 h (reaction time). The actual experimental yield was 21.98% at optimum conditions, which is close to the maximum predicted value of 22.80%.