On “Pinning” Domain Growth in Two-Phase Polymer Liquids

Abstract

What has been reported as "pinning" or severely reduced growth rates of phase-separated domains in off-critical polymer blends is shown to be the normal effect of crossover between two kinetic regimes associated with morphology of the liquid-liquid system. The bicontinuous liquid microstructure formed by spinodal decomposition grows rapidly by hydrodynamic coarsening where size ξ h ∼ Lt until the percolated system dissociates into droplets. The droplets then grow by classical coarsening with radius increasing as r j 3 ∼ Kt, where K may be calculated for Ostwald ripening and/or coalescence with no impediments to mobility at any size scale. Apparent pinning persists for the induction period ∆t ≈ r j 3 /K required for the slower particle growth to be observed, and the characteristic r j ∝ t 1/3 behavior is not recovered for approximately 10∆t. Numerical simulations of spinodal decomposition in polymer blends, which to date omit hydrodynamics, are unable to capture the change in growth mechanism and rate on switching from percolated to droplet morphology.

Factors affecting size and swelling of poly(ethylene glycol) microspheres formed in aqueous sodium sulfate solutions without surfactants

“…4B). A linear relationship was found between the mean diameter of the phase-separated domains and time, which is expected in the early stages of phase separation [23]. A plateau in coarsening was reached 3–5 minutes after phase separation that may correspond to a percolation-to-cluster transition [23].…”

Synthesis and characterization of nanoporous polycaprolactone membranes via thermally- and nonsolvent-induced phase separations for biomedical device application

“…Moreover, the nucleation growth rate at the late stage of spinodal decomposition [41] and other models, such as droplet coalescence and Ostwald ripening, can be expressed as:…”

Kinetics of thermally induced phase separation in ternary polymer solutions. II. Comparison of theory and experiment

“…(4) for our system. Recent studies 17,18 also point out that the use of eq. 4 to analyze coarsening data is more accurate than analyses based on the more traditional power-law fits (q m ϳ t Ϫ␣ ) to data plotted on a log-log scale.…”