Non-Equilibrium Pattern Formation in the Crystallization of Polymer Blend Films
V Ferreiro, Jack F. Douglas, James A. Warren, Alamgir Karim
The crystallization of polymeric and metallic materials normally occurs under conditions far from equilibrium. The morphologies formed reflect a competition between order associated with the symmetries of the equilibrium crystal geometry and disorder associated with diffusive, convective and elastic deformation processes necessary for the large-scale growth of the non-equilibrium crystallization patterns. This competition between orderly and disorderly growth also occurs in a wide range of other pattern formation processes [growth of cell colonies, electrochemical deposition, flame fronts, fluid flow in inhomogeneous media, fracture of inhomogeneous materials, etc.]. To better understand non-equilibrium pattern formation, polymer and metal crystallization in particular, it is important to have experimental and computational model systems that can be tuned through the recognized class of pattern type and to determine the properties (interaction parameters) and processes that govern the morphology diagrams of both the measurements and simulations. We show that the crystallization of polyethylene oxide (PEO) in a thin film (L = 2000 ) geometry can be tuned to obtain spherulitic, seaweed, regular dendritic and fractal aggregation forms through the addition of clay particles and the amorphous polymer, polymethyl methacrylate (PMMA). The clay particles act as nucleating centers and as a source of disorder in the crystallization process. The nearly two-dimensional polymer crystallization patterns (seaweed and regular dendrites) closely resemble phase-field simulations of non-equilibrium crystallization in a model two-dimensional liquid mixture having a variable surface tension anisotropy, e. We suggest that a competition between phase separation and crystallization in the blend films is responsible for a variable e and the observed variability of the crystallization morphology with polymer composition.
Physical Review E (Statistical, Nonlinear, and Soft Matter Physics)
, Douglas, J.
, Warren, J.
and Karim, A.
Non-Equilibrium Pattern Formation in the Crystallization of Polymer Blend Films, Physical Review E (Statistical, Nonlinear, and Soft Matter Physics), [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=851746
(Accessed November 28, 2023)