Synchrotron Small-Angle X-Ray Scattering Studies on Phase Transitions in Block Copolymers and Crystalline Polymers under High Pressure
Grant-in-Aid for Scientific Research (B)
|Allocation Type||Single-year Grants|
|Research Institution||Kyoto Institute of Technology|
SAKURAI Shinichi Kyoto Institute of Technology, Department of Polymer Science & Engineering, 繊維学部, 助教授 (90215682)
|Project Period (FY)
2003 – 2004
Completed(Fiscal Year 2004)
|Budget Amount *help
¥5,700,000 (Direct Cost : ¥5,700,000)
Fiscal Year 2004 : ¥600,000 (Direct Cost : ¥600,000)
Fiscal Year 2003 : ¥5,100,000 (Direct Cost : ¥5,100,000)
|Keywords||High Pressure / Block Copolymer / Crystalline Polymer / Phase Transition / Synchrotron / Small-Angle X-Ray Scattering / Nanostructure / ANBC-22 / 圧力依存性 / ミクロ相分離構造 / 小角X線散乱 / シンクロトロン / 配向制御 / シリンダー構造 / 自発的配向 / 秩序-無秩序転移 / 球構造 / 規則性|
In this study, we have focused on the following three topics :
(1)Effects of High Pressure on Phase Transition Temperatures in Block Copolymers
(2)Effects of High Pressure on Spontaneous Orientation of Microdomains in Block Copolymers
(3)High Pressure Phase Transitions in Origomeric Block Copolymers (Low-Molecular Weight Liquid Crystalline Compound ANBC-22)
For this purpose, high-brilliance X-rays from synchrotron radiation source at SPring-8 (Hyogo, Japan) were used and time-resolved two-dimensional small-angle X-ray scattering (2d-SAXS) measurements were conducted upon pressure jump. The results obtained are briefly summarized.
(1)The order-disorder transition temperature (T^<ODT>) of sphere-forming block copolymers was determined by SAXS as a function of pressure. T^<ODT> was found to increase with an increase of pressure. According to the Clapeyron-Clausius equation, it can be concluded that the ODT is an endothermic transition, although DSC can hardly detect the endotherm upon the ODT.
Therefore, we can show significance of studies of high pressure.
(2)Effects of high pressure on the spontaneous ordering of cylindrical microdomains were investigated. It has been discovered in our previous study that slightly shear-oriented cylinders can spontaneously improve their orientation when the sample is further annealed even in the absence of shear flow. The degree of orientation exhibited an interesting behavior when the sample was subjected to continuous heating, such that the degree of orientation started to increase above a certain temperature T_L until temperature reached T_H, above which it turned to decrease rapidly down to zero (no appreciable orientation). As the pressure was increased, T_L decreased whereas T_H increased. Thus, T_L is found to have no relevance to the glass transition temperature. At a first glance, T_H can be taken as the T^<ODT> because not only orientation of cylinders but also cylinders themselves disappear above T^<ODT>. However, it has been found that T_H is lower than T^<ODT>, namely cylinder orientation spoiled without dissolution of cylinders. This is an interesting result which deserves a future problem.
High pressure phase transitions and phase behaviors for low-molecular weight liquid crystalline compound ANBC-22 (4'-22-docosyloxy-3'-nitrobiphenyl-4-carboxylic acids) were studied. The reason of this study is to examine phase transition phenomena in this curious material which has an aspect of origomeric block copolymers. As a matter of fact, the ANBC-22 exhibits cubic (bicontinuous) phases with Ia3d and Im3m symmetries. Under the ambient pressure, the phase behavior is such that smectic C (SmC) to Im3m to Ia3d with increasing temperature. Note here that the block copolymer double gyroid structure also has the Ia3d cubic symmetry. Among interesting results by SAXS, the study of structural transformation from SmC to Im3m under 35 MPa in the range of 130〜175℃ is mentioned here. Upon the transformation, immatured Im3m appeared and this was co-existent with SmC for ca. 7℃ and gradually turned into a firm Im3m structure. It is interesting to point out here that the co-existing SmC phase displayed discontinuous change in peak position during the structural transformation (SmC to Im3m), indicating the spacing of the layered structure discontinuously changed. Less
Research Products (14results)