Structure Formation during Induction Period before Crystal Nucleation

It was considered in polymer crystallization process that no structure formation occurred during induction period before crystal nucleation. However we found that spinodal decomposition type phase separation occurs before crystal nucleation due to orientation fluctuations of stiff segments. Er presented the following scenario for the structure formation and confirmed experimentally.

1) Change of chain conformation, confirmed by IR measurements. Ex, PE: gauche to trans

2) Increase in length of stiff segments, confirmed by SANS with d-labeling

3) Increase in excluded volume of stiff segments
Excluded volume： b=d (diameter of stiff segment）
Increase in free energy (system becomes unstable)

Polymer, 33, 4451 (1992)

Polymer, 33, 4457 (1992)

Phys. Rev. Lett., 71, 25, 4163-4165 (1993)

Phys. Rev., B52, 12696-12704 (1995)
Macromolecules, 32, 8932-8937 (1999)

Phys. Rev., E65, 0618011-0618017 (2002)

Adv. Polym. Sci., 191, 187 (2005)

4) Parallel orientation of stiff segments, confirmed by depolarized light scattering.

Decrease in free energy (system is stabilized)

Critical concentration:

5) Microscopic phase separation due to orientation fluctuations (Doi’s theory)
Spinodal decomposition type phase separation