論文内容の要旨
Fuminori Arai （新井史紀）

The crystallization behavior and higher-order structure formation in multicomponent polymer systems
containing crystalline components are governed by the following contributing factors: the dilution effect on
the crystallization by the amorphous component, the competition between the crystallization and moleculardiffusion, and the interplay between the crystallization and liquid-liquid phase separation (LLPS).

In thisstudy, based on these factors, the crystallization kinetics and the lamellar structure formation in crystalline
polymer blends were revealed, using small-angle X-ray scattering (SAXS) and wide-angle X-ray
diffraction (WAXD) techniques, differential scanning calorimetry (DSC) and polarized and phase-contrast
optical microscopies.
In Chapter 1, the crystallization behavior and the higher-order structure formation in the miscible
crystalline/amorphous blend composed of poly(vinylidene fluoride) (PVDF) and isotactic-poly(methylmethacrylate) (i-PMMA) were investigated, where i-PMMA, which is crystallizable, was in an amorphousstate during the crystallization of PVDF because of its extremely slower crystallization.

As is expected

for a typical miscible crystalline/amorphous blend, PVDF exhibited depressions of both the overall
crystallization rate and the melting temperature depending on the blend composition.

In the formation of

the crystalline lamella, the amorphous i-PMMA component was included between the PVDF crystalline
lamellae and increased the spacing in the PVDF-rich blends.

However, the inclusion of i-PMMA into theinterlamellar region was limited in the PVDF-poor blends, i.e., a part of i-PMMA was excluded from theregion.

These results were attributed to the competition between the crystallization of PVDF and themolecular diffusion of i-PMMA; the crystallization rate of PVDF becomes lowered relative to the diffusion
rate of i-PMMA, as the content of PVDF decreases.
In Chapter 2, the subsequent crystallization of i-PMMA after completion of the crystallization of PVDF
was investigated, that is the crystallization under the pre-formed higher-order structure of PVDF.

Theoverall crystallization rate of the subsequent crystallization of i-PMMA was enhanced, in which theinduction period for the nucleation of i-PMMA in the blends was remarkably shortened compared to that inthe neat i-PMMA. It was concluded that this shortened induction period arose from the role of thepre-existing PVDF crystals as a nucleating agent.

The morphological parameters such as the long period,crystalline lamellar thickness and interlamellar spacing estimated from the SAXS experiments indicatedthat i-PMMA was crystallized between the PVDF crystalline lamellae and further expanded that spacing.
In the blend that contains relatively less i-PMMA content, a confined crystallization of i-PMMA wassuggested by the depression of the Avrami index, the lower crystallinity of i-PMMA and the limited spaceof the crystallizable region (interlamellar region of the pre-formed PVDF crystal).
In Chapter 3, the crystallization occurring simultaneously with LLPS was presented, using apartly-miscible crystalline/amorphous blend system composed of poly(ethylene glycol) and i-PMMA,
which has an upper critical solution temperature (UCST)-type LLPS phase diagram.
i-PMMA was again dealt with as an amorphous component.

In this system,

When the crystallization of PEG occurs

simultaneously with the spinodal decomposition, the overall crystallization rate was more enhanced athigher crystallization temperatures Tc.

This unique behavior is different from the result deduced from theusual crystallization mechanism that the crystallization is slower at higher Tc.

Therefore, it was concluded

that this enhancement could be explained by the fluctuation-assisted secondary nucleation based on theMitra-Muthukumar theory that the smaller quench depth from the spinodal temperature contributes to fasternucleation.

In the crystalline lamellar formation, it was indicated that i-PMMA component was excluded

from the interlamellar region during the crystallization of PEG.
In Chapter 4, the spherulite growth of poly(ɛ-caprolactone) (PCL) in blends with styrene-oligomer (SO)was evaluated mainly using the time-resolved phase-contrast and polarized microscopies.

As someresearchers reported, the PCL spherulite growth accompanied by the exclusion of SO component from thespherulite was observed, in which the droplet-like SO domains were observed at the spherulite growth front
in the blend composition of LLPS.

The SO droplets interfere with the spherulite growth for a while, andthen these were disappeared in the matrix at the late stage of crystallization.

With the disappearance of

the SO droplets, the spherulite growth was recovered.
In Chapter 5, finally, the crystallization behavior and higher-order structure of a polymer with a specificmolecular shape, the star-like polymer and its blends with the linear polymer, were investigated using
well-characterized poly(tetrahydrofuran) (PTHF).

In the crystallization of the neat star PTHF, higher

nucleation density and lower spherulite growth were observed by comparing to those in the linear PTHF.
These results were attributed to the higher chain density and lower molecular mobility of the star PTHF,respectively. In the blends of the linear and star PTHFs, generating nuclei in the star-rich blends was as
many as in the neat star PTHF.
blend composition.

On the other hand, the spherulite growth rate varied linearly with theFrom these results, it was concluded that the nucleation is governed by a major

component polymer in the blends, whereas the spherulite growth progresses cooperatively without
distinction between the linear and star polymers.