(728h) Multiscale Modelling of Macromolecule Self-Assembly in Solution: The Case of Poly-ε-Caprolactone in Acetone-Water Mixtures

Authors: 
Marchisio, D., Politecnico di Torino
Carbone, P., The University of Manchester
This work focuses on macromolecule (poly-ε-caprolactone, PCL) self-assembly in acetone-water mixtures. By mixing an acetone (“good” solvent) solution containing PCL molecules with water (“bad” solvent, or anti-solvent) their self-assembly in molecular clusters (or nanoparticles) is induced. The aim of this work is to simulate this process by using a diffusion-limited aggregation (DLA) model, that assumes that PCL molecules self-assemble together through an irreversible process, by means of the Smoluchowski population balance model (PBM), solved in turn with the quadrature method of moments (QMOM) inside a computational fluid dynamics (CFD) code. It is assumed that molecule and cluster aggregation is caused by Brownian motions and turbulent fluctuations. The aggregation process is described in terms of the cluster mass distribution (CMD) that quantifies the number of macromolecules in each molecular cluster. The relationship between the number of macromolecules per cluster and their radius of gyration is formulated in terms of the Flory law, whose coefficient and exponent are calculated from molecular dynamics (MD) simulations performed in a previous work. Model predictions are validated against experiments performed in a confined impinging jets mixer (CIJM) by varying the operating conditions, namely the initial PCL concentration, PCL molecular weight and mixing rate of the acetone and water solutions, resulting in very goos agreement.