Nanoparticle Ordering in Semicrystalline Polymers

One way to engineer the macroscopic properties of a crystalline polymer matrix is to place nanoparticles into them, but in an organized manner. We have recently found that NP organization can be controlled by varying the crystal growth rate. We develop a coarse-grained model to study this situation – in particular, we focus on the out-of-equilibrium dynamics of nanoparticles being pushed/engulfed by a solidification front depending on crystallization velocity $v_{s}$. Particle engulfment occurs when $v_{s}$ is higher than a critical velocity $v_{c}$. When $v_{s}$ is smaller than $v_{c}$, particles are pushed by the crystallization front and organize in a 2-D plane. Even though most models for particle engulfment consider dynamic force equilibrium at $v_{c}$, we show the system is not in equilibrium in this regime. Thus, we consider conditions for engulfment based on particle velocity with respect to crystal growth rate. Our results agree with experimental observations on anisotropic organization of nanoparticles in semicrystalline polymers driven by crystallization speed.