factors during spinodal decomposition: the maximum of the structure factors
increases with time but the peak location does not change at the early stage,
implying that C2 solution performs phase separation prior to crystal nucleation.
In contrast, Fig.11.5bshows the typical evolution of structure factors during the
nucleation and growth: the maximum of structure factors is relatively small, and the
peak location shifts to smaller wave vectors with increase of time, implying that C3
solution performs a conventional crystal nucleation and growth. The spinodal
decomposition of C2 solution generates a bi-continuous morphology structure at
the early stage. Accordingly, the concentrated domains are much smaller and more
uniform in sizes, and meanwhile more spatially homogeneous for the formation of a
thermoreversible gel (see Fig.11.6a), in comparison to the nucleation-dominated
C3 solution (see Fig.11.6b). Such a structure can be frozen by the subsequent fast
crystallization. The micro-pore structures fabricated via two-step separate phase
transitions have been widely applied in the production of separation membranes
and foam materials of semi-crystalline polymers.
11.4 Accelerated Crystal Nucleation at Liquid Interfaces
Liquid interfaces are prevailing within the immiscible polymer blends and solutions.
The effect of interfaces to polymer crystallization cannot be overlooked, not only
because the practical system accumulates impurities at interfaces for heterogeneous
crystal nucleation, but also because the thermodynamic conditions for crystal nucle-
ation at interfaces are different from that in the bulk phase. The latter effect can be
revealed by the theoretical phase diagrams for immiscible polymer blends, as
Fig. 11.6 Snapshots of crystalline morphologies obtained from the simulations of isothermal
crystallization in homogeneous C2 (a) and C3 (b) solutions with the concentration 0.125 at the
temperature 1.5Ec/k. The cubic lattice space is 64^3 , and each polymer chain contains
128 monomers (Zha and Hu 2007 ) (Reprinted with permission)
230 11 Interplay Between Phase Separation and Polymer Crystallization