| Summary: | 碩士 === 國立中興大學 === 化學工程學系所 === 102 === The purpose of this research is to modify the graphene oxide (GO) by grafting poly(methyl methacrylate) (PMMA) functionalized on graphene oxide surface (PGO) and by reducing modified graphene oxide (PGO-r) in order to remove oxidized functional groups. Afterward, PGO and PGO-r
were adopted as Pickering emulsion agents for emulsifying the oil phase,1,6-Heaxanediol diacrylate (HDDA) in water. Therefore, the study of emulsion diameter and morphology was investigated. Finally, solid porous Pickering films were produced by UV-polymerization, then further reduced. Afterward, compare the conductivity was measured before and after solid porous film reduced.
In this thesis, we assume that the cation exchange capacity(CEC) of graphene oxide is the same with montmorillonite. PGO was prepared initially to form bilayer micelles on graphene oxide surface using vinylbenzyl dimethyl dodecyl ammonium chloride (VBDDAC) and cetyltrimethyl ammonium bromide (CTAB). Then, we added the
vinyl-containing monomers such as methyl methacrylate (MMA) and polymerized on the graphene oxide surface by admicellar polymerization.
Two systems were classified. System (I) is GO adsorbing VBDDAC at 0.5times CEC (PGO-5V), and system (Ⅱ) is GO adsorbing VBDDAC at 0.75times CEC (PGO-7.5V). Before polymerization, GO is prepared with grind or non-grind, then forms PGO-5V. Further reduction of PGO-5V and PGO-7.5V were done by using hydrazine.
Through the analysis of PGO and PGO-r by FTIR, the C-Hstretching vibration can occur at 2952 cm-1. 1731 cm-1 for C=O stretching vibration, 1452 cm-1 for CH3 stretching vibration, and 1149 cm-1 for O-CH3 stretching vibration. These stretching vibration spectra indicate PMMA had successfully polymerized on the surface of graphene oxide.
The diffraction peak of PGO-5V is at 2θ equals 8 o, which corresponds to a d-spacing of 1.1 nm. The diffraction peak does not emerge PGO-5V(g) and PGO-7.5V between 2θ= 1.5 o~10 o , and the d-spacing is larger than 5.88 nm which indicates the delamination of GO. The sample of PGO-5V-r
does not have the diffraction peaks because the stacking order was random,and exhibit an amorphous diffraction shoulder around 20 o. Similar to PGO-5V, the diffraction peak was not found for PGO-5V(g)-r and PGO-7.5V-r between 2θ = 1.5 o ~10 o. There are two possibilities that make this scenario happen. First, the exfoliation still exists after reduced reaction. Second, the stacking order was random. Through static water contact angle measurements, the contact angles for GO, PGO-5V,PGO-5V(g), and PGO-7.5V were determined as 40.3 o, 59.9 o, 69.5 o, and 82.3o. The contact angle increases as the grafting of PMMA increases. After reduction, the contact angles for GO-r, PGO-5V-r, and PGO-5V-r resulted as 65.5 o、 65. 7 o and 89.6o. The reason for these changes in contact angles was due to removal of oxygen functional groups hydrazine.
Pickering emulsions were prepared by system (Ⅰ) and system (Ⅱ) modified graphene oxides, which were used as an emulsifier for HDDA and water. The emulsion type of PGO-5V, PGO-5V(g) and PGO-7.5V are all W/O. The samples of PGO-5V for the volume ratio for water to HDDA 0.25, 0.5, and 1, emulsion average particle size is 137 μm, 258 μm and
399 μm respectively. The samples of PGO-5V(g)with the volume ratio for water to HDDA 0.25, 0.5, and 1, emulsion average particle sizes are 76 μm, 145 μm and 351 μm. The samples of PGO-7.5Vwith the volume ratio for water to HDDA 0.25, 0.5, and 1, emulsion average particle size is 47 μm,
52 μm and 87 μm respectively. The emulsion type of PGO-5V-r and PGO-7.5V-r are all W/O. The samples of PGO-5V-r with the volume ratio for water to HDDA 0.25, 0.5, and 1, emulsion average emulsion particle size is 635 μm,1055 μm and 1790 μm respectively. Samples of PGO-7.5V-r with the volume ratio for water to HDDA 0.25, 0.5, and 1, emulsion average emulsion particle size is 132 μm,141 μm and 164 μm
respectively. In observation of these samples, the particle sizes were larger for samples after reduction reactions. The reason is due to the aggregation on graphene oxide during the reduction procedure due to the poor
dispersion of graphene oxide in the continuous phase. PGO-5V had a greater emulsion size than PGO-7.5V because there are less grafted PMMA which cause the surface less hydrophobic.
Finally, solid Pickering films were produced by UV-polymerization of HDDA phase in W/O emulsions using PGO-5V at a volume ratio 0.25. This sample was further reduced by hydrazine. By analyzing the SEM, many 50 to 60 nm sphere particles inside the bubble can be observed in the film. The formation of these particles is due to HDDA being slightly dissolved in the water. After the UV-polymerization, the HDDA segments start to forms micelles to proceed the polymerization. The process is also
similar to emulsifier-free polymerization. By analyzing the conductivity with the modified graphene oxide weight ratio of 1 wt %、2 wt %、3 wt %, it was found that the conductivity was 1.86×10-16 , 2.84×10-16 , and 3.40×10-16 S/cm, respectively. After reducing PGO, the conductivity was improved to 5.78×10-16, 8.62×10-16 , and 1.18×10-15 S/cm respectively.
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