Polymer-polymer miscibility in PEO/cationic starch and PEO/hydrophobic starch blends

The main purposes were evaluating the influence of different starches on the miscibility with Poly(ethylene oxide) (PEO) and their effects on the spherulite growth rate. Polymer-polymer miscibility in PEO/cationic starch and PEO/hydrophobic starch blends consisting of different w/w ratios (100/0, 95/05, 90/10, 80/20, 70/30, 65/35 and 60/40) was investigated. This analysis was based on the depression in the equilibrium melting temperature (T-m(0)). By treating the data of thermal analysis (Differential Scanning Calorimetry - DSC) with Nishi-Wang equation, a positive value (0.68) was found for the interaction parameter of PEO/cationic starch. For PEO/hydrophobic starch blends, a negative value (-0.63) was obtained for the interaction parameter. The results suggested that PEO/cationic starch system should be immiscible. However, the system PEO/hydrophobic starch was considered to be miscible in the whole range of studied compositions. Through optical microscopy analysis, it was concluded that the spherulite growth rate is significantly affected by changing the amount and the type of starch as well.