Lai Har Sim

ATR-FTIR studies on ion interaction of lithium perchlorate in polyacrylate/poly(ethylene oxide) blends

The interaction behaviours between components of polyacrylate (PAc)/poly(ethylene oxide) (PEO) and lithium perchlorate (LiClO(4)) were investigated in detail by Attenuated Total Reflectance (ATR)-Fourier Transformed Infrared (FTIR) spectroscopy. Solution cast films of the PAc/PEO and PAc/PEO/LiClO(4) were examined. No obvious shifting of the characteristic ether and ester group stretching modes of PEO and PAc was observed, indicating incompatibility of the binary PAc/PEO blend. The spectroscopic studies on the PAc/PEO/LiClO(4) blends reveal that Li(+) ions coordinate individually to the polymer components at the ether oxygen of PEO and the C-O of the ester group of PAc. Frequency changes observed on the nu(C-O-C) and omega(CH(2)) of PEO confirm the coordination between PEO and Li(+) ions resulting in crystallinity suppression of PEO. The absence of experimental evidence on the formation of PEO-Li(+)-PAc complexes suggests that LiClO(4) does not enhance the compatibility of PAc/PEO blend.

Conductivity and dielectric relaxation of Li salt in poly(ethylene oxide) and epoxidized natural rubber polymer electrolytes

Two types of polymer electrolytes were studied: poly(ethylene oxide) (PEO) and epoxidized natural rubber (ENR) both filled with lithium perchlorate. Universal dielectric behavior and impedance relaxation were investigated at room temperature over a wide range of salt concentration. Complex impedance plots exhibit one semicircle in some cases (PEO polymer electrolytes) with an extended spike at low frequencies. This implies a double layer capacity strongly influences conductivity at low frequencies. In the ENR–salt system, semicircles can be obtained only at very high concentrations. This points towards stable resistor dominated networks only develop at very high salt concentrations for this system. Centers of the semicircles lie below real axis indicating non-Debye dielectric relaxation. The relaxation peak broadens and shifts to higher frequencies with increasing salt content. It indicates that the relaxation time of polarization relaxations decreases with ascending salt content. Relaxations occur at extremely low salt concentrations in PEO and only at very high salt concentrations in ENR. Hence, conductivity of ENR–salt is one to two orders of magnitude lower as for PEO–salt.

Compatibility and conductivity of LiClO4 free and doped polyacrylate – poly(ethylene oxide) blends

Abstract Thermal behaviour of polyacrylate (PAc)/poly(ethylene oxide) (PEO) and PAc/PEO doped with LiClO4 were investigated by differential scanning calorimetry. The constituents, PAc and PEO, show immiscibility after glass transition temperature T g analysis. The addition of LiClO4 increases the T gs of neat PAc, PEO and their blends. The conductivities at 30°C of PAc, PAc/PEO 40 : 60 doped with 15 wt-% LiClO4 and PEO are 8·3 × 10–10, 1·2 × 10–6 and 7·9 × 10–6 S cm–1 respectively. Reasonably high conductivity of the PAc/PEO/LiClO4 blends makes it a potential polymer electrolyte.

Ionic transport and glass transition temperature of polyether–salt complexes: dependence on molecular mass of polymer

Abstract Poly(ethylene oxide) (PEO) of different molecular masses (Mη = 6×105, 1×106 and 4×106 g mol−1) and lithium perchlorate complexes were prepared by solution casting method. The salt concentrations of the samples were varied between 2 and 23 wt-%. Room temperature (30°C) conductivity, glass transition temperature and Fourier transform infrared spectroscopy (FTIR) for the samples are reported. The conductivities acquired at 13 wt-% salt concentration for PEO with Mη = 6×105, 1×106 and 4×106 g mol−1 are 9×10−6, 1×10−4 and 7×10−4 S cm−1 respectively. This indicates that higher molecular mass PEO samples exhibit higher conductivity. An interesting trend is found for variation in glass transition temperature Tg with variation in concentration of complexing salt. It shows a linear variation until ∼13 wt-% and then slowly levels off. The slope of the linear region is found to be dependent on the polymer molecular masses. The rise in Tg for each salt concentration increases linearly with ascending molecular mass of PEO. This suggests that PEO with higher molecular mass exhibits greater extent of complexation with LiClO4 as supported by FTIR studies.

Melting behaviour, morphology and conductivity of solid solutions of PEO/PAc blends and LiClO4

Abstract The melting behaviours of poly(ethylene oxide)/polyacrylate (PEO/PAc) and PEO/PAc doped with LiClO4 were investigated by differential scanning calorimetry. The equilibrium melting temperature and the crystallinity of PEO show no significant variation with the addition of PAc but are suppressed by the incorporation of LiClO4. The deformed structure of PEO spherulite resulting from disrupted crystallisation is observed in salt doped PEO and its blends. Conductivity as a function of salt concentration is studied using the power law. Lower ion mobility and correlation of ions for PAc corroborate with its lower conductivity as compared to PEO. Despite a reasonable amount of LiClO4 being solvated by PAc, the conductivity of the solid solutions of PEO/PAc blends is primarily governed by PEO.

Selective localization of lithium perchlorate in immiscible blends of poly(ethylene oxide) and epoxidized natural rubber

Immiscible blends of poly(ethylene oxide) (PEO) and epoxidized natural rubber (ENR) comprising of lithium perchlorate (LiClO4) were prepared by solution casting method. Blends of PEO and ENR are found to be thermodynamically immiscible via thermal analysis and the result has been reported previously. It is also noted in the previous study that LiClO4 dissolves preferentially in PEO than in ENR. Fourier-transform infrared (FTIR) spectroscopic studies on the blends of PEO/ENR and PEO/ENR/LiClO4 at all compositions in this work aim at investigating the ion-dipole interactions between the Li+ ions and the polymer components of the PEO/ENR/LiClO4 blends from a different approach so as to verify the selective localization of the salt in the different phases of the blends. FTIR results show that Li+ ions coordinate individually to the neat polymers of the PEO/ENR/LiClO4 blends at the ether oxygen of PEO and the oxirane group of ENR. Spectroscopic studies reveal again the preferential solubility of the salt in PEO.

Miscibility and Conductivities of PEO/PMMA-LiClO4 Solid Polymer Electrolyte

Thin films of poly (ethylene oxide) (PEO), poly (methyl methacrylate) (PMMA) and selected blends of PEO/PMMA with and without the addition of LiClO4 were prepared using solution casting technique. The presence of a single Tg which corresponds closely to that of the Gordon Taylor equation confirms the miscibility of both the salt-free and salt-doped blends. The Tgs and the ion conductivity (σ) at room temperature of PEO, PMMA and the PEO/PMMA blends generally increase with ascending salt concentration (Y). Variations in the σ value as a function of Y for all the three systems correlate closely with their respective Tg results. PMMA-salt complex records the lowest σ value at all salt concentrations. PEO/PMMA/LiClO4 blend with 75 wt% PEO exhibits the highest σ value of 5 x 10-7 S cm-1 at Y = 0.10. The σ value of the blend-salt system is observed to be slightly lower than that of the PEO-salt system. This is due to reduced segmental motion cause by increased Tg of the blend and a decrease in free ions in the amorphous phase of PEO as a small amount of the salt is solvated by PMMA in the blend. Therefore, the percolation path lies in the amorphous PEO rich phase of the blend.

The influence of the amorphous polymer on conductivity, morphologies and thermal properties of polyether-based blends with addition of inorganic salt

Thermodynamic control of the dispersion of lithium (Li) salt in different phases of semicrystalline/amorphous polymer blends is elucidated in this study. Solid polymer electrolytes of poly(ethylene oxide) (PEO), epoxidized natural rubber (ENR), random copolymer of poly(acrylate) (PAc) and as well as polymer blends of PEO with ENR and PAc doped with various concentrations of Li salt were studied. The salt concentrations (CLi) of solid polymer electrolytes vary between CLi = 0.02 and 0.15. The influence of the ENR or PAc on the properties of PEO after addition of Li salt is discussed. Blends of PEO/ENR and PEO/PAc are immiscible by elucidation of the glass transition temperature (Tg) as well as the morphological analyses. PEO, ENR and PAc possess oxygen in their respective chemical structures, which may be able to coordinate with the Li salt added. Non uniformity of Li salt concentration in different phases of the blends is highlighted for both systems. The conductivity of PEO/ENR and PEO/PAc blends doped w...

Phase behaviour and morphology of composite comprising of poly(ethylene oxide), polyacrylate and lithium perchlorate

Thin films of poly(ethylene oxide) (PEO) and polyacrylate (PAc) blend and the composite PEO/PAc/lithium perchlorate (LiClO4) are prepared via solution casting method. Thermal analysis using differential scanning calorimetry depicts that both the PEO/PAc blend and the PEO/PAc/LiClO4 composite form single phase systems, as evident from the presence of single composition-dependant glass transition temperature (Tg). Polarized optical microscopy (POM) was applied to study the spherulite growth rate and morphology of PEO in both the PEO/PAc blend and PEO/PAc/LiClO4 composite. Homogeneity in the phase behaviour of the PEO/PAc blend and the PEO/PAc/LiClO4 composite is reaffirmed by the continuous suppression of the growth rate and the severe deformation and coarseness of the PEO spherulite with ascending PAc content in the blend and increasing LiClO4 concentration in the composite. Additionally, the amount of salt that causes macro-phase separation in the neat polymers and the PEO/PAc blends is governed by the coordination ability of the polymer, especially PEO, to the Li+ ion. Results from both thermal analysis and POM reflect the higher preference of LiClO4 for PEO than PAc. Therefore, PEO/PAc 85/15 blend is observed to exhibit the highest capability to interact with the Li+ ion.

Effect of epoxidation level on thermal properties and ionic conductivity of epoxidized natural rubber solid polymer nanocomposite electrolytes

Effect of epoxide content on the thermal and conductivity properties of epoxidized natural rubber (ENR) solid polymer nanocomposite electrolytes was investigated. Commercial available epoxidized natural rubber having 25 (ENR25) and 50 mole% (ENR50) epoxide, respectively were incorporated with lithium perchlorate (LiClO4) salt and titanium dioxide (TiO2) nanofiller via solution casting method. The solid polymer nanocomposite electrolytes were characterized by differential scanning calorimetry (DSC) and impedance spectroscopy (IS) for their thermal properties and conductivity, respectively. It was evident that introduction of LiClO4 causes a greater increase in glass transition temperature (Tg) and ionic conductivity of ENR50 as compared to ENR25. Upon addition of TiO2 in ENR/LiClO4 system, a remarkable Tg elevation was observed for both ENRs where ENR50 reveals a more pronounced changes. It is interesting to note that they exhibit different phenomenon in ionic conductivity with TiO2 loading where ENR25 sho...