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somebody post dis
“i’v already SPOKEN our LOVE is BROKEN i don’t want to do this any LONGER…“
Y do we need to broke the LOVE? god help us…
My life is brilliant.
My love is pure.
I saw an angel.
Of that I’m sure….
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sejak balik phuket ari2, banyak lak tawaran yg dtg kat aku, doc aku minta aku isi job application kat website UKM untuk jawatan Research Officer (RO). wow! dat my dreaming job ever. doc suh aku isi n antar salinan kat Prof. uhuhuu.. terharu la ng doc coz sudi rekemen aku tuk job tu. and ari2 gak aku taw akak se-Lab dapat National Fellowship (NSF), alhamdullilah. setelah 2x g intervw akhirnya dapat gak biasiswa tu, igt xdpt dah ari2. tawakal jer la..
Then the next day, ari selasa lak Doc carik lagi, dis time doc suh jumpa Assoc. Prof program Kimia. my godness, dis time doc nominate aku tuk g germany. tuk menghadiri 59th Meeting of Nobel laureates in chemistry. nomination jerla, then intervw jap ng assoc. prof. n aku diberi borang nomination untuk di isi. huhuu… bayak lak bende kena isi huhuu… plus nak kena wat “Letter of Interest n Letter of Support lak” leceh2, but nak xnak aku kena la mengarang gak, tgh wat la ni
Hari rabu lak terus ade intervw tuk jawatan RO huhuu.. everything goin smoothly but time last skali diorg bukak skrol tgk nama ” MOHD FAIZ JALAJALHU SARJANA MUDA SENIBINA” yallah aku silap bawk skrol huhuuu…aku g bwk skrol housemate aku lak celakakak tul huhuu….
nak wat cmne dah, pasrah jerla tawakal jerla
ni lak list yang sepatutnya g interview but juz 5org jer yg hadir, kak wahida, anuar, azmi, fairuz and me. harap2 adala peluang
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welll…dis is wat actually happen during, afta n be4 da conference,
penat gak r, coz sblumni baru jer balik dari penang n dpt la rest kejap sehari 2. then continue wif this conference lak. actually hari ahad 30NOV tu kami dah ke TIara Beach untuk registration tapi disebabkan kelupaan tahap dewa aku tak bawa dokumen yang diperlukan untuk registration. so kak aminah jerla yang dpt register n membawa pulang beg labtop pemberian seketriat RCSSST2008 manakala shwu peng ng aku hanyalah menjadi peneman sahajo hahaa.. buang masa dan tenaga sahaja. yang bagusnya kami dpt la booking hotel kat Eagle Ranch Resort dulu.
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This paper was presented at 24th REGIONAL CONFERENCE ON SOLID STATE SCIENCE AND TECHNOLOGY 2008 (RCSSST 2008) at Tiara Beach Resort, Port Dickson, Negeri Sembilan, Malaysia.
49% Poly(Methyl Methacrylate)-Grafted Natural Rubber Based Solid Polymer Electrolytes.
1M.S. Su’ait, 1*A. Ahmad, 1H. Hamzah and 2M.Y.A. Rahman
1 School of Chemical Sciences and Food Technology, Faculty of Sciences and Technology, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor, Malaysia.
2 College of Engineering, Universiti Tenaga Nasional, 43009 Kajang, Selangor, Malaysia.
*Corresponding Author : (azizan@ukm.my)
Abstract: The potential of 49% poly(methyl methacrylate)–grafted natural rubber (MG49) as a solid polymer electrolyte (SPE) film in rechargeable batteries system has been investigated. The flat, thin and flexible films were prepared by solution casting technique. The ionic conductivity was investigated by alternating current impedance spectroscopy (AC EIS). The highest conductivity was given by 20 wt. % of LiBF4 salt loading with 2.26×10-7 S.cm-1 whereas 4.00×10-8 S.cm-1 by 15 wt. % LiClO4 salt loading. The observation on structural studies done by X-ray diffraction (XRD) showed the amorphous phase to be appearing at the highest conductivity.
Keywords: Ionic conductivity, 49% poly(methyl methacrylate)–grafted natural rubber, Solid polymer electrolyte
1. Introduction
Research on polymer electrolyte was first conducted by Fenton et al. (1973). They found that the non conducting polymer, polyethylene oxide (PEO) became conducting when lithium salt was added into the polymer matrix. The finding of ionic conductivity in these polymer material complexes with salt has led to the development of electrochemical devices such as rechargeable batteries, electrocromic windows and sensing device for chemicals/gases usage [1].
Recently, modified natural rubber (NR) based SPE had grab draw the attention for many researchers. This is due to its attractive attributes such as low glass transition temperature (Tg), soft elastomer characterization at room temperature, and good elasticity. Suitable elasticity can result in flat, thin, and flexible film. Furthermore, modified NR gives excellent contact between an electrolytic layer and an electrode in battery system. It could also act as a polymeric solvent and the ionic conductivity is higher compared to glassy or crystalline state of polymer [2]. On the other hand, certain of modified NR such as epoxidized natural rubber (ENR) and poly(methyl methacrylate)–grafted natural rubber (MG) both possess oxygen atoms, which can act as electron donor atoms in the structure of the polymer host. The oxygen atoms with lone pair of electron formed a coordinate bond with Li+. Fig. 1 shows the structure of MG monomer. ion from perchlorate salt, producing a polymer-complex [8]. However, ENR based SPE shows a drawback to its mechanical properties such as slightly sticky and difficult to peel off from substrate [4,5] as compared to MG film which is more free standing, elastic and flexible. Previous studies on various MG were conducted elsewhere [2,3,6-9]
Fig. 1. Structure of MG monomer
In this work, MG49 is doped with lithium salts such as LiClO4 and LiBF4 to prepare SPE by solution casting technique [2,3,6,8,9]. All samples were characterized by using AC impedence spectroscopy (EIS) and X-ray diffraction (XRD). It is expected that LiClO4 and LiBF4 salt to acquire different optimum ionic conductivity due to the differences in the anion size and lattice energy of appropriate salt.
2.Experimental and characterization
2.1 Materials.
MG49 was commercially obtained. Lithium perchlorate (LiClO4) salt was supplied by Fluka, while lithium tetrafluoroborate (LiBF4) salt by Aldrich. All the materials were used without further purification.
2.2 Sample preparation.
All the polymer electrolyte samples were prepared by solution casting technique. MG49 rubber was sliced into a grain size. The quantity of MG49 was dissolved in stopped flasks containing toluene. After 24 hours, the solution is stirred with efficient magnetic stirring for the next 24 hours until complete dissolution of MG49 into clear viscous solution. LiClO4 salt solution was prepared separately in THF solution and stirred for 12 hours. These two solutions were then mixed together for 24 hours to obtain a homogenous solution. The electrolyte solutions were then casted onto a glass Petri dish and the solvent were allowed to slowly evaporate in a fume hood at room temperature. A free standing film was obtained when the solvent completely evaporated. Residual solvents were then removed in vacuum oven for 48 hours at 50C. The samples were then stored in a desiccator until further use. The same experimental procedure is repeated for LiBF4 salt.
2.3 Characterization.
The ionic conductivity measurements were carried out by AC impedance spectroscopy using high frequency resonance analyzer (HFRA) model 1255 with applied frequency from 6500 Hz to 0.1 Hz at perturbation voltage of 2500 mV. The disc shaped sample of 16 mm in diameter was sandwiched between two stainless steel block electrodes. The measurements were conducted at room temperature.The ionic conductivity (σ) was calculated from the bulk resistance (Rb) obtained from the intercept on real impedance axis, the film thickness (l), and the product of effective contact area (A) according to the equationσ= [ l/(A Rb) ]. X-ray diffraction model D5000 Siemens is used to observe on the appearance and disappearance of crystalline or amorphous phase as a function of salts content. The data were collected from the range of diffraction angle 2θ from 20° to 80° at rate 0.05° s-1.The analysis was conducted at room temperature.
3. Results and Discussion
3.1. Ionic conductivity
Typical impedance plots are shown in Fig. 2. Ionic conductivity and O/Li ratio of solid polymer electrolyte MG49-LiClO4 and MG49-LiBF4 are shown in Table 1 and had been expressed into a graph in Fig. 3. The graph shows the ionic conductivity increases with the increasing of salt loading up until the optimum level in polymer host due to the increasing of the number of conducting species in the electrolyte. Ionic conductivity without salt content (0 wt. % salt) is 1.03×10-12 S.cm-1. The highest conductivity, given by 20 wt. % of LiBF4 salt loading in MG49 is 2.26×10-7 S.cm-1 while 15 wt. % LiClO4 salt loading is 4.00×10-8 S.cm-1. This optimum value shows the maximum and an effective interaction between oxygen atoms and lithium ion in the electrolyte. However, our finding of LiClO4 salt is slightly lower than the finding by Alias et al. [6]. In contrast, our finding of LiBF4 salt is slightly higher. They founded that the ionic conductivity of MG49 with 30 wt. % of LiCF3SO3 is 1.76 x 10-7 S.cm-1.
(a)
(b)
Fig. 2 Typical impedance plot for (a) MG49-LiClO4 and (b) MG49- LiBF4
|
wt. % salt loading |
Conductivity, σ (S.cm⁻¹) |
O/Li Ratio |
||
|
MG49 + LiClO₄ |
MG49 + LiBF4 |
MG49 + LiClO₄ |
MG49 + LiBF4 |
|
|
0 |
1.03E-12 |
1.03E-12 |
- |
- |
|
5 |
4.42E-10 |
3.35E-12 |
51/1 |
45/1 |
|
10 |
2.72E-09 |
7.77E-12 |
26/1 |
23/1 |
|
15 |
4.00E-08 |
3.01E-11 |
17/1 |
15/1 |
|
20 |
1.25E-09 |
2.26E-07 |
13/1 |
11/1 |
|
25 |
4.23E-10 |
9.63E-10 |
9/1 |
8/1 |
Table 1 The ionic conductivity and O/Li ratio of SPE MG49-LiClO4 and MG49-LiBF4
Fig. 3 The ionic conductivity of SPE MG49-LiClO4 and MG49-LiBF4
The interaction was explained by FTIR investigated by Kamuta et al. [12] shows that a coordinate bond was formed in the complexes between lithium ion and oxygen atoms. The O/Li ratio for the optimum LiBF4 salt loading is 11 of oxygen atoms to 1 lithium ion or simply wrote 11/1 compared to the optimum LiClO4 salt loading which is 17/1. The different value in O/Li is due to the differences in the molar mass and weight percent of the lithium salt. The main reason LiBF4 salt has a higher ionic conductivity as compared to LiClO4 salt due to the differences in anion size and lattice energy of appropriate salt. LiBF4 salt has low lattice energy due to the delocalization of large anion’s charge as compared to LiClO4 salt [1]. Nevertheless, the ionic conductivity decrease rapidly after the optimum salt loading because of the ion association or ion aggregation [9]. However these findings are slightly lower than the finding by Idris et al. [2] and Ali et al. [9]. This is because in this research, there is no plasticizer such as polypropylene carbonate (PC) and ethylene carbonate (EC) added into the SPE. The presence of PC and EC in polymer electrolyte can easily corrode the lithium metal electrode in electrochemical cell [5].
3.2. Structural studies
The XRD analysis is used to determine the structure and crystallization of polymer host by observing the appearance and disappearance of crystalline or amorphous region. Fig. 4 (a) and (b) shows the XRD diffractograms for SPE MG49-LiClO4 and LiClO4 salt. While, Fig. 5 (a) and (b) shows the XRD diffractograms for SPE MG49-LiBF4 and LiBF4 salt respectively. The intense peak shows the crystalline region occurs in the polymer host. The amorphous region occurs when the intensity of the peak became broader [10]. Fig. 4 (b) illustrated that the intense peak of LiClO4 showed at 21.1°, 23.3°, 31.7°, 33.1°, 35.7°, 39.5° and 47.3°. Moreover, Fig. 5 (b) shows an intense peak of LiBF4 at 21.4°, 23.6°, 26.8°, 28.2°, 32.0°, 32.8°, 39.9°, 44.6° and 54.9°. Pure MG49 in Fig. 4 (b) and 5 (b) showed a single peak at 26.6° that belongs to MMA monomer in rubber chain. With addition of salt content from 5 wt. % to 25 wt. %, the MMA single peak at 26.6° disappear and it only appears after the addition of 25 wt. % of LiClO4 salt.
As mentioned earlier, the highest ionic conductivity doped with 15 wt. % of LiClO4 salt and 20 wt. % of LiBF4salt loading respectively. From the XRD patterns in Fig. 4 (a) and 5 (a), the highest ionic conductivity are located at 15 wt. % of LiClO4 salt and 20 wt. % of LiBF4salt loading which have a broadening intensity. In other word, amorphous region appears in polymer host. This finding approved the suggestion from elsewhere [1,2,4,6,9-11] that amorphous region provides high ionic conductivity compared to the crystalline or semi-crystalline region. The different of the crystallization in both salts can also be observed via the intense peak. The presence of LiClO4 peaks at angle around 23°, 35° and 47° in Fig. 4 (a) and LiBF4 peaks at angle 28° in Fig. 5 (a) showed that the crystalline phase occurred after the maximum conductivity in SPE MG49 doped with lithium salts due to the ion association between cation and anion, respectively in the electrolyte at the high salt concentration. The salt affects the overall conductivity through crystalline complexes formation, intramolecular crosslinking of the polymer chains and the degree of salt dissociation-number of charge carriers [1].
(a)
(b)
Fig. 4. XRD diffractograms for (a) MG49-LiClO4 and (b) LiClO4 salt
(a)
(b)
Fig. 5. XRD diffractograms for (a) MG49-LiBF4 and (b) LiBF4 salt
4. Conclusion
The film of SPE MG49 doped with lithium salts (LiClO4 and LiBF4) have been successfully prepared by solution casting technique.The highest conductivity for LiBF4 salt was 20 wt. %, and for LiClO4 salt was 15 wt. %. The ionic conductivities obtained are within the range of ~10-8-10-7 S.cm-1 at room temperature. The observation on structural studies done by X-ray diffraction (XRD) showed the amorphous phase to be appearing at the highest conductivity.
5. Acknowledgements:
The authors would like to extend their gratitude towards Polymer Research Center (PORCE), Universiti Kebangsaan Malaysia for allowing this research to be carried out. This work is supported by the MOSTI grant 03-01-02-SF0423.
6. References
[1]F.M. Gary (1997). Polymer electrolytes, London: RCS Monographs, The Royal Society of Chemistry.
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[3]K. Kamuta and Y. Alias (2006). FTIR spectra of plasticized grafted natural rubber-LiCF3SO3 electrolytes. Journal of Spectrochimica Acta Part A 64, 442-447.
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[5]G. Lu, Z-F. Li, S-D. Li and J. Xie (2001). Blends of natural rubber latex and methyl methacrylate-grafted rubber latex. J. Applied Polymer Sciences 85, 1736–1741.
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[8]K. Kamuta, Y. Alias and R. Said (2005).FTIR and thermal studies of modified natural rubber based solid polymer electrolytes. Journal of Ionics 11: 472-476.
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