Thermoplastic starch plasticized by an ionic liquid

Thermoplastic starch (TPS) plasticized by 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) was obtained by melt processing. The resulting electrically conductive TPS samples were less hygroscopic than glycerol plasticized TPS samples. Despite this lower water uptake, [BMIM]Cl seems to be intrinsically a more efficient plasticizer of starch. [BMIM]Cl plasticized TPS samples show a much higher elongation at break in the rubbery state than the glycerol plasticized TPS samples. Their unusually low rubbery Young's modulus for thermoplastic starch (0.5 MPa) suggests a strong reduction of hydrogen bonds between the starch chains due to the presence of the ionic liquid. A detailed IR spectroscopy analysis supports this interpretation.