Early Stages of Nucleation and Growth in a Polymer Blend

The early stages of nucleation and growth in a mixture of high polymers were studied by time-resolved neutron scattering. During the first 160 min, a slow clustering was evident, indicating a buildup of concentration fluctuations. The clusters formed at the end of this stage had the characteristics of “critical nuclei,” because phase separation proceeded rapidly after their formation. At this stage, the scattering profiles showed a peak at finite wave vectors $\left(q_{\max }\right)$. The scaling exponents for the time dependence of the peak intensity and $q_{\max }$ are inconsistent with current theories.