The Studies of Self-assembling Behavior of Block Copolymers

• Main Authors: Sen-Chi Hung, 洪伸錡
• Other Authors: Chung-Yuan Nou
• Format: Others
• Language: zh-TW
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/02983738229988647692

博士 === 國立臺灣大學 === 化學研究所 === 93 === Abstract Hexagonal ordered mesoporous silica materials SBA-15 were synthesized using triblock copolymers and tetraethoxysilane by Zhao et al, but the high cost of silicon alkoxides was undesired features of preparative chemistry. Sodium silicate is a good candidate to replace the silicon alkoxides as the silica source. Mesoporous silica materials with tunable microporosity were synthesized starting from sodium silicate solutions and a triblock copolymer surfactant Pluronic 123 (EO20PO70EO20, Mav = 5800). The ratio of microporous volume (Vmp) of porous volume (VP) in SBA-15 can be tailored by the choice of stirring temperature and the H+/Si molar ratio (PSR) controlled the pH of reaction system. SBA-15 materials with different PSR were synthesized at stirring temperatures between 30 and 50 ℃. At 30 ℃, materials synthesized with a PSR of 1.03 proved to have a bigger pore size than materials synthesized with higher PSR resulting in SBA-15 with a larger micropore volume. The PSR and the stirring temperatures proved to play an important role in the material formed. This study focuses on a thourough investigation of PSR and the stirring temperature on the material characteristics using powder X-ray diffraction (XRD), nitrogen adsorption-desorption isotherm, thermogravimetric analysis (TGA), 29Si solid-state NMR, 129Xe NMR, and TEM. Our laboratory developed ternary surfactants systems (CTAB-SDS-P123) to construct SBA-15 silica platelets with perpendicular-nanochannels. Ionic surfactants, CTAB and SDS, would alternately array to form bilayer structure then create a lamellar confined space. Nonionic surfactant, P123, would be inserted into the lamellar confined space and formed hexagonal ordered array. In this report, we transferred the ternary surfactants systems onto the wafer surface via modification of positive charge. SBA-15 silica thin films with perpendicular-nanochannels were formed as the addition of sodium silicate solution with the pH value adjusted to between 5 and 6. The physical properties of these materials were characterized using powder X-ray diffraction (XRD) and SEM. Atom transfer radical polymerization (ATRP) of the alkyne-functional monomer 4-(trimethylsilylethynyl)styrene allowed to preparation of block copolymers with narrow molecular weight distributions (1.28). After removing TMS, the ethyne-functional copolymer could be coupled with aryl iodide. Nitroxide-mediated radical polymerization (NMRP) of the alkyne-functional monomer 4-((4-methoxyphenyl)ethynyl)styrene allowed the preparation of block copolymers with narrow molecular weight distributions (1.15). At higher conversions, side reactions, including addition of mediating nitroxides to alkyne groups, led to broader molecular weight distributions. While poly((4-(4-methoxyphenyl)ethynyl)styrene) blocks of moderate molecular weight had a fair degree of miscibility with polystyrene, the pendant alkyne groups of these copolymers led to microphase-segregated materials.