Nanoparticle Formation by Amphiphilic Block Copolymer Directed Assembly: A Model Study Using Molecular/brownian Dynamics Simulations
Chungyin Cheng, Chemical and Biological Engineering, Iowa State University, Ames, IA 50011, Monica H. Lamm, Department of Chemical and Biological Engineering, Iowa State University/DOE Ames Laboratory, A510 Zaffarano Hall, Ames, IA 50011, R. O. Fox, Department of Chemical & Biological Engineering, Iowa State University, 2114 Sweeney Hall, Ames, IA 50011-2230, and R. Dennis Vigil, Iowa State University, 2114 Sweeney Hall, Ames, IA 50011.
Nanoprecipitation  is a process to produce functional nanoparticles protected by amphiphilic copolymer directed assembly. In this process, organic drug and copolymers are dissolved in solvent and rapidly mixed with nonsolvent in a customized micro-device to create high supersaturation. The growth of nanoparticles is kinetically arrested by block copolymer assembly on the surface of the organic drug, and therefore a tunable and narrow particle size distribution is achievable. The Nanoprecipitation process has been studied in several aspects: CFD simulations were performed to investigate the turbulent flow and mixing evaluation of the micro-reactor, microPIV experiments were conducted to furthermore validate the models, and a population balance model has been developed to account for the particulate flow system. To have a more fundamental understanding of the process, a computational simulation of this system is performed using Brownian dynamics (BD), as well as molecular dynamics (MD), and compared with detailed mechanistic model for micellization kinetics. Each organic particle is represented by a coarse-grained (CG) bead, and the diblock copolymer chain is constructed from a series of CG beads, each of which represents a polymer unit with bead-spring potential. The simulation results are analyzed to obtain information about characteristic precipitation time, aggregation numbers and particle sizes. These data are compared with the experimental data and used to validate a population balance model.
 B. K. Johnson and R. K. Prud'homme. Flash nanoprecipitation of organic actives and block copolymers using a confined impinging jets mixer. Australian Journal Of Chemistry, 56(10):1021–1024, 2003.