String Formation in Sheared Polymer Blends: Coalescence, Breakup and Finite Size Effects
Kalman D. Migler
We have discovered a droplet-string transition in concentrated polymer blends which occurs when the size of a dispersed droplet becomes comparable to the gap width between the shearing disks. The transition occurs over a shear rate interval of ~2% and proceeds via the coalescence of O(10E4) droplets in a four stage kinetic process. Once formed, the strings are stable and exhibit pronounced hysteresis. The droplet-string transition is a manifestation of the weakening of the Rayleigh-Tomatika instability due to finite size effects. Possible applications of this new morphology and processing strategy include ultra-thin materials of high one-dimensional strength, polymer blend wires, and novel polymeric scaffolds.