A Computational Study of the Polymerization‐Induced Phase Separation Phenomenon in Polymer Solutions under a Temperature Gradient

Abstract

This paper studied the polymerization‐induced phase separation phenomenon (spinodal decomposition) in a model binary polymer solution under a linear spatial temperature gradient for the purpose of fabricating anisotropic polymeric materials by using mathematical modeling and computer simulation. Reaction kinetics were incorporated with the non‐linear Cahn‐Hilliard theory and the Flory‐Huggins free energy expression in the model. Moreover, the slow mode theory and Rouse law were used to account for polymer diffusion. It was found that an anisotropic morphology was obtained when a temperature gradient was imposed along the polymer solution sample. The direction of the structural anisotropy, however, depended significantly on the overall phase separation time. The presence of a temperature gradient along the polymer solution sample generated a spatial variation in polymerization rate, which resulted in a spatial variation of quench depth. Consequently, at a given instant, the phase separation at different locations of the polymer solution was at different stages of spinodal decomposition. The droplet size formed along the polymer solution was therefore dependent on the polymerization rate, the quench depth and the stage of spinodal decomposition. Furthermore, the spatial temperature gradient produced a spatial variation in the process induction time, which contains the polymerization induction time and phase separation induction time. It was also found that the polymerization induction time played a significant role on the spatial variation in the overall process induction time.image

Thermal Patterning of a Critical Polymer Blend

“…2(a 0 ), 2(b 0 ), and 2(c 0 ) ] with otherwise identical parameters by setting D T 0 in Eq. (7). All other parameters of the model were kept constant and the same initial conditions were used [ Fig.…”

“…Yamamura et al [4] observed the formation of stripe patterns in demixing fluids caused by thermocapillary flow and Okinaka et al [5] describe directional phase separation of a polymer blend driven by a temperature gradient. Lee et al [6,7] performed a computational study on the spinodal decomposition process within a temperature gradient. Spatially periodic patterns formed after driving a binary polymer mixture periodically above and below the instability [8].…”

Effect of Concentration Gradient on the Morphology Development in Polymer Solutions Undergoing Thermally Induced Phase Separation

“…For instance, the permeability, throughput, and cleanability improve significantly for a polymer membrane with anisotropic pore size 7–10. Structural morphology can be influenced by imposing an external fluctuation, such as an electric field,11, 12 concentration gradient,13, 14 shear flow,15 or temperature gradient 16–18. For instance, Lee et al16–18 simulated a phase separation phenomenon via spinodal decomposition under a spatial temperature gradient (off‐critical quench) for both thermal‐induced and polymerization‐induced phase separation processes.…”

The Ludwig‐Soret Effect on the Thermally Induced Phase Separation Process in Polymer Solutions: A Computational Study

“…Isothermal static and dynamical properties of polymer blends or solutions have been all well established; [27,28] however, there have been few experimental [29][30][31][32] or numerical studies [21,22] reported in the literature on the phase-separating polymer solutions and/or polymer blends under the influence of an externally applied…”