Crystallization from SAXS

In conclusion of the melting behavior of PTeOX, the endothamic profiles of PTeOX prepared below 90 °C is different from that prepared above 90 °C. From the results of the X-ray diffraction, mentioned in Section 2, can be seen that the polymerization of T OX in the solid state produces the main and sub-crystals below 90 °C, while the main crystal and a aystal corresponding to 100 A scattering in SAXS are formed above 90 °C. Chatani et al. used PT OX prepared at 62 C to show main and sub-crystals from WAXS study, and Amano et al. used PTeOX prepared at 100 °C to w only lamellar type crystals from SAXS and EM studies. Both results seem to be somewhat similar, but we can not compare their data since the characteristics of PTeOX prepared at different temperatures are different. PTeOX prepared at 100 °C contains the main crystals beside lamellar type crystals as mentioned later. 

Direct evidence of nucleation during the induction period will also solve a recent argument within the field of polymer science as to whether the mechanism of the induction of polymers is related to the nucleation process or to the phase separation process (including spinodal decomposition). The latter was proposed by Imai et al. based on SAXS observation of so-called cold crystallization from the quenched glass (amorphous state) of polyethylene terephthalate) (PET) [19]. They supposed that the latter mechanism could be expanded to the usual melt crystallization, but there is no experimental support for the supposition. Our results will confirm that the nucleation mechanism is correct, in the case of melt crystallization. 

Fig. 4 SAXS curves of PET crystallized from the glassy state at 80 °C as a function of annealing time [7]...

Fig. 25 Annealing time evolution of the difference SAXS intensity in the induction period (a) and the crystallization period (b) for the melt crystallization of PET at 244 °C [18]. This system corresponds to crystallization from the metastable state where a nucle-ation and growth type of primary phase separation first occurs followed by the spinodal decomposition type secondary phase separation...

Fig. 5.19 Domain spacing (top line) obtained from SAXS for copolymer PEO75PBO54 as a function of time during the melting and crystallization programme indicated by the lower line (Mai el al. 1997). The melt has a gyroid structure.

Fig. 5.38 Normalized intensities obtained from SAXS data for the isothermal crystallization of a PCL-PB diblock (Mw = 12.5 kg mol 45% PCL) following a quench from the homogeneous melt to 26.5 °C (Tom is close to Tm for this polymer) (Nojima et al. 1992a) ( ) melt peak (o) crystal peak. The peak position was found not to change on crystallization.

Fig. 35 Crystallization of non-spherical particles homogeneously coated with DNA. (a, b) Schematic of a hexagonal close-packed 2D layer in assemblies of gold nanorods and corresponding structure factor S(q) obtained from SAXS measurements (blue line) and simulations (red line), (c, d) Schematic of ID columnar assembly of gold triangular nanoprisms and corresponding SAXS patterns, (e, f) Schematic of the 3D fee assembly of gold rhombic dodecahedra (the lines indicate the fee unit cell) and corresponding SAXS patterns. Adapted with permission from [152]...

Figure 9 SAXS intensity profile for the series of samples solution-crystallized from 0.05 to 0.5 wt % tetralin solution. The background was subtracted from original data plots.

The structure of PE-PEE,PE-PEP andPE-PVCH diblocks upon crystallization from the ordered melt has been elucidated using simultaneous SAXS, WAXS and DSC [9,11]. Here, PEE and PEP are rubbery components, whereas PVCH=po-ly(vinycyclohexane) is glassy below a glass transition temperature Tg 140 °C. It was observed that the melt morphologies were destroyed due to PE chain folding... 

The orientation of crystalline stems with respect to the interface of the microstructure in block copolymers depends on both morphology and the speed of chain diffusion, which is controlled by block copolymer molecular weight and the crystallization protocol (i.e. cooling rate). In contrast to homopolymers, where folding of chains occurs such that stems are always perpendicular to the lamellar interface, a parallel orientation was observed for block copolymers crystallized from a lamellar melt phase perpendicular folding was observed in a cylindrical microstructure. Both orientations are shown in Fig. 8. Chain orientation can be probed via combined SAXS and WAXS on specimens oriented by shear or compression. In PE, for example, the orientation of (110) and (200) WAXS reflections with respect to Bragg peaks from the microstructure in the SAXS pattern enables the unit cell orientation to be deduced. Since PE stems are known to be oriented along the c axis, the chain orientation with respect to the microstructure can be determined. 

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