Induction period of crystallization

But there are two important unresolved questions regarding the mechanism of crystallization the first question is are the primary nuclei actually formed from the earliest stage ( induction period ) of crystallization and the second is what is the role of the topological nature of polymers in the polymer crystallization mechanism ... 

Below, Doi s theory is first elucidated in some detail, and then our experimental results will be shown to support the partial extension of polymer chains during the induction period of crystallization which triggers the parallel orientation of the stiff segments. 

Fig. 13 Schematic diagram showing the change of chain conformation, i.e., coil to helix, during the induction period of crystallization for sPS and iPS...

Fig. 15 1224 cm-1 band assigned to the crystalline chain packing of the a-crystal phase of sPS as a function of annealing time at 120 °C, which appears only after the induction period of crystallization 30 min [12]... 

Fig. 21 Annealing time dependence of the integrated DPLS intensity for iPS in the induction period of crystallization at 135 °C [15]...

The Mechanism of Structure Formation During the Induction Period of Crystallization from the Unstable State... 

Fig. 24 Schematic diagram of a model for the structure formation mechanism in the induction period of crystallization from the unstable state...

Imai, M., Kaji, K. and Kanaya, T., Structural formation of polyethylene terephthalate) during the induction period of crystallization. 3. Evolution of density fluctuations to lamellar crystal, Macromolecules, 27, 7103-7108 (1994). 

Yoshihashi Y, lijima H, Yonemochi E, Terada K (2006) Estimation of physical stability of amorphous solid dispersion using differential scamiing calorimetry. J Therm Anal Caloiim 85 689-692 Yoshihashi Y, Yonemochi E, Maeda Y, Terada K (2010) Prediction of the induction period of crystallization of naproxen in solid dispersion using differential scanning calorimetry. J Therm Anal Calorim 99 15-19... 

Crystallization is faster than phase dissolution, and crystals pin the phase-separated structure so that phase dissolution cannot Phase dissolution is competing with crystallization Extremely long induction period of crystallization Before crystallization starts, phase dissolution finishes... 

Tashiro, K., Yoshioka, A. Molecular mechanism of solvent-induced crystallization of syndiotactic polystyrene glass. 2. Detection of enhanced motion of the amorphous chains in the induction period of crystallization. Macromolecules, 35(2), 410-414 (2002). 

We observe nano-nucleation directly by adding nucleating agent (NA) to a sample by which the SAXS intensity Ix(q, t) from the nano-nuclei increases as much as lO" times, where q is the scattering vector [18,19]. At the same time, we determine the correct y(A/, r) and the 2D shape of the nano-nucleus. In addition, obtaining the AT dependence of f N, t) directly by SAXS shows that nucleation controls the induction period of crystallization, while spinodal decomposition does not [20]. 

We describe the direct observation of the degree of supercooling (AT) dependence of f(N, t) by means of SAXS. f(N, t) increases rapidly with the increase of t at large AT, while f(N, t) increases more slowly at small AT. We obtain AT dependence of the onset time r(A7 defined as the extrapolated time of the linearly increasing f(N, t) with t. We describe the empirical formula by ir AT) oc exp[-yAT], where 7 is a constant that is, nucleation becomes impossible when AT approaches 0. We conclude that nucleation controls the induction period of crystallization, rather than the spinodal decomposition process. 

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