Synergistic plasticization effect of hyperbranched poly(1,4‐butanediol citrate)/glycerol on corn starch

Thermoplastic starch plasticized with glycerol is very sensitive to humidity and aging. In this study, hyperbranched poly(1,4‐butanediol citrate) is prepared via a one‐step method and mixed with glycerol as a co‐plasticizer of starch to prepare thermoplastic starch films. The structure of hyperbranched poly(1,4‐butanediol citrate) is studied by performing Fourier transform infrared spectroscopy and 1 H nuclear magnetic resonance analyses. The interaction between starch and co‐plasticizer, and crystallinity, mechanical properties, anti‐aging properties, thermal stability, transmittance and moisture absorption of the thermoplastic starch films are studied. The results illustrate that poly(1,4‐butanediol citrate)/glycerol has a synergistic effect on the toughness, anti‐aging properties, transmittance and moisture adsorption properties of the thermoplastic starch films. The thermoplastic starch film with a poly(1,4‐butanediol citrate)/glycerol weight ratio of 2:28 has the maximum elongation at break, the highest transmittance, the optimal ability to inhibit long‐term retrogradation of starch and the lowest moisture content at a relative humidity of 68%. Elongation at break of thermoplastic starch film with poly(1,4‐butanediol citrate)/glycerol at 2:28 and stored for 3 and 30 days is (101.1 ± 14.0)% and (91.7 ± 2.7)%, respectively, which are 1.8 and 4.4 times that of the thermoplastic starch film with only glycerol, respectively. These phenomena not only depend on the interaction between starch and co‐plasticizer, but also may be related to the compatibility between starch and co‐plasticizer. Thus, the poly(1,4‐butanediol citrate)/glycerol combination has potential applications in the preparation of thermoplastic starch.