STRUCTURAL COARSENING OF DEMIXED POLYMER-SOLUTIONS

The structural coarsening of demixed polystyrene/cyclohexane solutions was studied by using a quick freeze/freeze-dry technique on solutions allowed to coarsen for various lengths of time. Quenches of near-critical solutions were bicontinuous; however, the coarsening law was found to be consistent with a diffusive coarsening mechanism rather than the expected hydrodynamic flow mechanism. The structural size was found to grow with time with an exponent in the range 0.18-0.32. A quantitative model of the diffusive coarsening process was developed specifically for demixed polymer solutions, and predicted the structural sizes within a factor of 5 of the measured values. The model also predicted a very strong concentration dependence of coarsening, which was experimentally verified. An explanation as to why diffusive coarsening rather than coarsening by hydrodynamic flow occurs is offered. © 1990, American Chemical Society. All rights reserved.