Dissipative particle dynamics (DPD) simulation method and experimental study were used to study the formation of starch microspheres (SM). Cyclohexane was selected as oil phase, amylose as aqueous phase, meanwhile Span60 and Tween60 as emulsifiers, respectively. It is shown from DPD simulations that the forming process of SM is consisted of four steps: (1) irregular dispersion of amylose and emulsifiers, (2) the formation of small aggregates, (3) the formation of microspheres aggregates, (4) stabilization of microspheres. The simulation results represent that the oil-aqueous volume ratio is the key influencing factor to the formation of microspheres aggregates. When the oil-aqueous volume ratio is smaller than 7, aggregate morphologies of the aqueous phase as lamellar, columnar, crisscross and ellipsoidal structures are observed. Microspheres are formed only when oil-aqueous volume ratio is 8, and the particle sizes are decreased with the increase of oil-aqueous volume ratio. And the experiments show that the microspheres can not get good sphericity when oil-aqueous volume ratio is 8, and the particle sizes are decreased with the increase of oil-aqueous volume ratio when the ratio is 10 to 20. The experimental results could be interpreted with the simulation results. DPD simulation provides an insight into the microstructure of SM and help to analyze the experimental results, which is helpful in synthesis of SM.

Key words: starch microspheres, mesoscale simulation, dissipative particle dynamics (DPD)