Preparation and Characterization of Poly (2-Dimethylaminoethyl Methacrylate) Brush on the Silicon Surface for pH Responsive Property with Au Nanoparticle

• Main Authors: Ping-chun Pai, 白炳峻
• Other Authors: Jem-kun Chen
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/11447665171935398339

碩士 === 國立臺灣科技大學 === 高分子系 === 98 === Poly (2-Dimethylaminoethyl Methacrylate) (PDMAEMA) polymer brushes were grafted on the silicon surface by using atom transfer radical polymerization (ATRP). The silicon surface was treated by oxygen plasma, causing the sueface to become chemically modified (hydroxyl groups). 3-aminopropyltriethoxy silane (APTES) was used to react with the hydroxyl group on the surface, α-Bromoisobutyl bromide reacted with NH2 group of APTES to form halogen groups on chain ends to be the initiator of atom transfer radical reaction. Sequentially, PDMAEMA brushes were grafted on the silicon surface. Electron Spectroscopy for X-ray photoelectron spectroscopy (XPS) was utilized to verity the surface element of initiator and PDMAEMA polymer brushes for each stage. We observed coil-like structure with 10nm, 13nm, 19nm and 25nm of diameters for PDMAEMA brushes after grafting for 2, 4, 6 and 8 h by atomic force microscopy (AFM) and high-resolution thermal field emission scanning electron microscopy (HRFE-SEM). Approximately linear increase in thickness of the grafted PDMAEMA layer from 90.6 to 329.3 nm was observed on the surface upon increasing the polymerization time to 8 h. Furthermore, the patterned PDMAEMA brushes with width of 400 nm were fabricated by using lithography on the silicon wafer. The patterns of PDMAEMA brushes matched perfectly with the patterns from lithography, indicating that the patterned PDMAEMA could be fabricated by using a very-large-scale integration (VLSI) system to approach commercial application. Contact angles on the PDMAEMA layer increased to 61.5°at PH=1, but decreased to 72.5°at PH=11, indicating a PH responsive property on the surface. At a PH of 1, the tethered PDMAEMA stretched its polymer chains to increase the hydrogen bonding between water and polymer to create a hydrophilic surface. Upon increasing PH to 11, the tethered PDMAEMA collapsed due to disappearance of positive charges, increasing hydrogen bonding among polymer to create a hydrophobic surface. The PH responsive behavior of PDMAEMA polymer brushes repeated three cycles to verity the property. Moreover, PDMAEMA layer was used to be a extractor on the surface through the PH responsive property. The positive charge on the PDMAEMA attracted a herring sperm DNA with 10μg/μl at PH = 7, a DNA capture process. Upon increasing PH to 3, the positive charge groups disappeared, causing the release of the DNA. The results suggests that The results suggest that tethered PDMAEMA brushes could be a extractor to miniaturize cartridges of sample preparation for rapid disease diagnosis through fluid device to approach the lab-on-a-chip (LOC). The positive charge (R4N+) groups on the side chain of PDMAEMA brush were used to synthesize gold nanoparticles on the surface in water and toluene. The sizes of Au particles, synthesized in water and toluene, were 8 and 25nm, respectively. The Au particles on the PDMAEMA side chains reduced surface zeta potential from -10.36 to -16.98 mV, indicateing the Au particles carried negative charges which is induced by R4N+ groups.