| Summary: | 碩士 === 國立中興大學 === 化學工程學系所 === 101 === The main purpose of this study is to fabricate acrylate/clay nanocomposites by UV polymerization. In the beginning, we modified two kinds clay (MMT and Laponite) by ad-micellar polymerization to prepare modified clay. Second, we used the modified clay to stabilize the interface of HDDA monomer and water to form W/O Pickering emulsion. Finally, W/O Pickering emulsion was photopolymerized by UV light to get acrylate/clay nanocomposites. The emulsion diameter, morphology were investigated with different the oil/water weight ratios and polymers grafted on clay (MMT and Laponite) surface.
Modified clay was prepared by adding 0.5 CEC (cationic exchange capacity) VBDDAC (vinylbenzyl dodecyl dimethyl ammoniumchloride ) and 1.5 CEC CTAB (cetyltrimethyl ammonium bromide) to form bilayer micelles on clay’s surface via cation exchange, and then we added acrylate monomer such like BA (butyl acrylate), MMA (methyl methacrylate) and ST (styrene), and polymerized on clay surface by ad-micellar polymerization. We also used THF solvent to remove un-grafted polymer on clay surface. Two kinds of polymers were synthesized. Polymer I (BA/MMA copolymer) with different weight ratios on MMT and Laponite surface are called M5V15C-p-fBnM (f/n = 4/0, 2/2, 0/4) and L5V15C-p-jBkM (j/k= 2/0, 1/1, 0/2). Polymer II (BA/ST copolymer) with different weight ratios grafted on Laponite surface are called L5V15C-p-jBkS (j/k= 2/0, 1/1, 0/2). After FTIR analysis, we found the modified clay with grafted copolymers showed the signal of transmittance of carbonyl group (1730 cm-1) and revealed copolymers grafted successfully onto the surface of clay. According to the static water contact angle measurement, before extraction by THF, the contact angle of M5V15C-p-fBnM increases with increasing BA fraction and is between 73°~ 86°. After extraction by THF, the contact angle of M5V15C-p-fBnM is between 66°~ 74° after removing un-grafted polymer on MMT surface. Contact angles of L5V15C-p-jBkM and L5V15C-p-jBkS get the same trend with modified MMT. We also found that the contact angle of L5V15C-p-jBkM is larger than L5V15C-p-jBkS because of copolymers with longer side chains.
Pickering emulsions were prepared in HDDA and water, and the size distribution of emulsion stabilized by M5V15C-p-4B was larger than that of stabilized by M5V15C-p-4M. This is because the solubility parameter of PMMA (δ=19.0 J1/2/cm3/2) is closer to HDDA (δ=19.2 J1/2/cm3/2) than PBA(δ=18.3 J1/2/cm3/2). Furthermore, the size distribution of Pickering emulsion stabilized by extracted modified-clay was smaller than that of un-extracted one, because the un-grafted polymer chains on clay would produce the steric effect when clay ranked in the oil/water interface.
Two copolymers as emulsifiers were used for preparing the Pickering emulsions containing acrylate and water. Using L5V15C-p
-jBkM as the emulsifier will obtain the smaller emulsion particles than using L5V15C-p-jBkS. This can be explained by more carbonyl groups in BA/MMA copolymer than that of BA/ST copolymer. Laponite modified by MA/MMA copolymer is more compatible with HDDA than with BA/ST copolymer. Furthermore, the emulsion stabilized by extracted L5V15C-p-jBkM and L5V15C-p-jBkS will obtain larger emulsion size than that of un-extrcated. From results of TGA analysis, extracted Laponite had lower polymer content than that of un-extracted one, so the compatibility between the extracted Laponite and HDDA is inferior to that of un-extracted Laponite and HDDA.
Finally, we used the UV light to polymerize W/O Pickering emulsion using M5V15C-p-fBnM, L5V15C-p-jBkM and L5V15C-p
-jBkS as emulsifier to get the solid film. From SEM analysis, we confirm the modified clay exists at the interface between water and HDDA.
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