SiC>2 as silica gel, fused silica, or quartzite will react readily in ethylene glycol (EG) with 1 equiv of alkali (M) hydroxide (except Na) to produce, in essentially quantitative yield, monomeric pentacoordinate glycolato silicates [M(0CH2CH20)2Si0CH2CH20H] containing two bidentate glycol ligands and one monodentate ligand. On heating, one EG is lost per two monomer units forming dimeric species, [M2Si2(0CH2CH20)s], or polymers, C^OksL-The Na derivative precipitates out of solution as the dimer. In experiments run with fused silica, the dissolution process exhibits a first-order dependence on base concentration and silica surface area. The Ea for silica dissolution is 14 ± 2 kcal/mol with AH* % 11 kcal/mol and AS* % -44 cal/mol K. In the absence of base, the silica surface reacts with EG to form an alkoxy-modified surface as determined by diffuse reflectance FTIR spectroscopy (DRIFTS). In the presence of base, only hydroxyl groups are seen on the silica surface. A mechanism for dissolution is proposed based on these observations. The dissolution process appears to be relevant to the nonaqueous synthesis of zeolites, especially silica-sodalite (ZSM-5), which are prepared under very similar conditions. The monomeric, anionic glycolato silicates exhibit trigonal-bipyramidal geometry, with no apparent contact interactions between the anionic framework and the alkali metal counterions. The monomers, dimers and polymers are characterized by chemical analysis, X-ray powder diffractometry, FTIR, solution and solid-state MAS 29Si NMR, and thermal gravimetric analysis. The monomers dissolve readily in methanol but appear to do so via a ligandexchange process wherein some of the glycolato ligands are displaced by methoxy ligands. On heating, the dimers/polymers decompose to phase-pure alkali silicates.

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In the present work, five systems of samples have been prepared by the solution casting technique. These are the plasticized poly(methyl methacrylate) (PMMA-EC) system, the LiCF 3 SO 3 salted-poly(methyl methacrylate) (PMMA-LiCF 3 SO 3 ) system, the LiBF 4 salted-poly(methyl methacrylate) (PMMA-LiBF 4 ) system, the LiCF 3 SO 3 salted-poly(methyl methacrylate) containing a fixed amount of plasticizer ([PMMA-EC]-LiCF 3 SO 3 ) system, and the LiBF 4 salted-poly(methyl methacrylate) containing a fixed amount of plasticizer ([PMMA-EC]-LiBF 4 ) system. The conductivities of the films from each system are characterized by impedance spectroscopy. The room temperature conductivity in the pure PMMA sample and (PMMA-EC) system is 8.57×10 −13 and 2.71×10 −11 S cm −1 , respectively. The room conductivity for the highest conducting sample in the (PMMA-LiCF 3 SO 3 ), (PMMALiBF 4 ), ([PMMA-EC]-LiCF 3 SO 3 ), and ([PMMA-EC]-LiBF 4 ) systems is 3.97×10 −6 , 3.66×10 −7 , 3.40×10 −5 , and 4.07×10 −7 S cm −1 , respectively. The increase in conductivity is due to the increase in number of mobile ions, and decrease in conductivity is attributed to ion association. The increase and decrease in the number of ions can be implied from the dielectric constant, ɛ r -frequency plots. The conductivity-temperature studies are carried out in the temperature range between 303 and 373 K. The results show that the conductivity is increased when the temperature is increased and obeys Arrhenius rule. The plots of loss tangent against temperature at a fixed frequency have showed a peak at 333 K for the ([PMMA-EC]-LiBF 4 ) system and a peak at 363 K for the ([PMM-EC]-LiCF 3 SO 3 ) system. This peak could be attributed to β-relaxation, as the measurements were not carried out up to glass transition temperature, T g . It may be inferred that the plasticizer EC has dissociated more LiCF 3 SO 3 than LiBF 4 and shifted the loss tangent peak to a higher temperature.

The effects of ceramics fillers on the polymethylmethacrylate (PMMA)-based solid polymer electrolytes have been studied using ac impedance spectroscopy and infrared spectroscopy. The polymer film samples were prepared using solution cast technique, tetrahydrofuran (THF) used as a solvent, and ethylene carbonate (EC) has been used as plasticizer. Lithium triflate salt (LiCF 3 SO 3 ) has been incorporated into the polymer electrolyte systems. Two types of ceramic fillers, i.e., SiO 2 and Al 2 O 3 , were then implemented into the polymer electrolyte systems. The solutions were stirred for several hours before it is poured into petri dishes for drying under ambient air. After the film has formed, it was transferred into desiccator for further drying before the test. From the observation done by impedance spectroscopy, the room temperature conductivity for the highest conducting film from the (PMMA-ECLiCF 3 SO 3 ) system is 1.36×10 −5 S cm −1 . On addition of the SiO 2 filler and Al 2 O 3 filler, the conductivity are expected to increase in the order of ∼10 −4 S cm −1 . Infrared spectroscopy indicates complexation between the polymer and the plasticizer, the polymer and the salts, the plasticizer and the salts, and the polymer and the fillers. The interactions have been observed in the C=O band, C-O-C band, and the O-CH 3 band.

Abstract. Poly(methylmetacrylate)/poly(ethylene oxide) (PMMA/PEO) based polymer electrolytes were synthesized using the solution cast technique. Four systems of PMMA/PEO blends based polymer electrolytes films were investigated:PMMA/PEO + ethylene carbonate (EC) system, (3) PMMA/PEO + lithium hexafluorophosphate (LiPF6) system and (4) PMMA/PEO + EC + LiPF6 system. The polymer electrolytes films were characterized by Impedance Spectroscopy and Fourier Transform Infrared Spectroscopy (FTIR). The FTIR spectra show the complexation occurrring between the polymers, plasticizer and lithium salt. The FTIR results give further insight in the conductivity enhancement of PMMA/PEO blends based polymer electrolytes.