Synthesis, characterization and electrochemical properties of poly(methyl methacrylate)-grafted-poly(vinylidene fluoride-hexafluoropropylene) gel electrolytes

A new comb-like copolymer, poly(vinylidene fluoride-co-hexafluoropropylene)-g-poly(methyl methacrylate), or [P(VDF-HFP)-g-PMMA], was successfully synthesized through grafting in situ formed PMMA to the P(VDF-HFP) backbone. The composition of the P(VDF-HFP)-g-PMMA copolymer was characterized by Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA) and elemental analysis. X-Ray diffractometry (XRD) and differential scanning calorimetry (DSC) were used to examine the reduction in crystallinity of P(VDF-HFP) due to the anchoring of PMMA segments on it. Gel electrolyte membranes based on the resulting copolymer were prepared by the Bellcore process. The ionic conductivity of Li⁺ across the membranes and the related transference number were measured. A study of the interfacial stability between Li electrode and the P(VDF-HFP)-g-PMMA gel electrolyte was also conducted to evaluate the suitability of the P(VDF-HFP)-g-PMMA copolymer in rechargeable lithium and lithium-ion battery applications.     

Dielectric properties and fluctuating relaxation processes of poly(methyl methacrylate) based polymeric nanocomposite electrolytes

Solid polymer nanocomposite electrolytes (SPNEs) consisted of poly(methyl methacrylate) (PMMA) and lithium perchlorate (LiClO₄) of molar ratio C=O:Li⁺=4:1 with varying concentration of montmorillonite (MMT) clay as nanofiller have been prepared by classical solution casting and high intensity ultrasonic assisted solution casting methods. The dielectric/electrical dispersion behaviour of these electrolytes was studied by dielectric relaxation spectroscopy at ambient temperature. The dielectric loss tangent and electric modulus spectra have been analyzed for relaxation processes corresponding to the side groups rotation and the segmental motion of PMMA chain, which confirm their fluctuating behaviour with the sample preparation methods and also with change of MMT concentration. The feasibility of these relaxation fluctuations has been explained using a transient complex structural model based on Lewis acid–base interactions. The low permittivity and moderate dc ionic conductivity at ambient temperature suggest the suitability of these electrolytes in fabrication of ion conducting electrochromic devices and lithium ion batteries. The amorphous behaviour and the exfoliated/intercalated MMT structures of these nanocomposite electrolytes were confirmed by X-ray diffraction measurements.     

Electrical properties of multi-walled carbon nanotube/poly(methyl methacrylate) nanocomposite

Multi-walled carbon nanotube (MWNT) nanocomposites with poly(methyl methacrylate) were prepared via both an in situ bulk polymerization and a suspension polymerization using a radical initiator of 2,2-azobisisobutyronitrile (AIBN). Prior to the synthesis, the MWNT was purified in an acidic solution to remove impurities such as metallic catalysts and amorphous carbons. The AIBN induced PMMA was grafted on the MWNT, which was confirmed by a Fourier transform infrared spectrometer (FT-IR). The composite morphology of the MWNT was observed by scanning electron microscopy (SEM). Electrical characteristics were further examined via both a four-probe method and a rotational rheometer equipped with a high voltage generator.     

Preparation and properties of transparent poly(methyl methacrylate) nanocomposite films

PMMA nanocomposites based on the synthetic smectite were prepared and characterized. The synthetic smectites, STN and SPN, were effectively hybridized in the PMMA matrix, as confirmed by X-ray diffraction patterns and by transmission electron microscopy, and optical and thermal properties were measured. The morphologies of PMMA nanocomposite films, containing 1–9 wt% with respect to synthetic smectite, were defined as exfoliated-immiscible and exfoliated-intercalated nanocompostites for CHT and CHP series, respectively. The optical properties, such as haze and UV transmittance, were maintained for organoclay loading of 9 wt% for CHP series. Thermal stability evaluated by TGA showed a small increase in the maximum decomposition temperature (T _d); however, the coefficient of thermal expansion (CTE) dramatically decreased with the amount of organoclay content. The storage modulus and loss modulus increased with the weight fraction of organoclay.     

Preparation of superhydrophobic poly(methyl methacrylate)-silicon dioxide nanocomposite films

Superhydrophobic poly(methyl methacrylate)-SiO₂ (coded as PMMA-SiO₂) nanocomposite films with micro-nanohierarchical structure were prepared via a simple approach in the absence of low surface-energy compounds. By spin-coating the suspension of hydrophobic silica (SiO₂) nanoparticles dispersed in PMMA solution, target nanocomposite films were obtained on glass slides. The wetting behavior of PMMA-SiO₂ nanocomposite films was investigated in relation to the dosage of SiO₂ nanoparticles dispersed in PMMA solution. It was found that hydrophilic PMMA film was transferred to superhydrophobic PMMA-SiO₂ nanocomposite films when hydrophobic SiO₂ nanoparticles were introduced into the PMMA solution at a high enough dosage (0.2 g and above). Resultant PMMA-SiO₂ nanocomposite films had a static water contact angle of above 162°, showing promising applications in selfcleaning and waterproof for outer wall of building, outer covering for automobile, sanitary wares, and so forth.     

Raman spectroscopy of conducting poly (methyl methacrylate)/polyaniline dodecylbenzenesulfonate blends

Polyaniline soluble in organic solvents was prepared using dodecylbenzenesulphonic acid (DBSA) as functional dopant. The solubility parameter was calculated and the most suitable solvent chloroform was checked for the solubility and the most compatible polymer PMMA was selected for blending. Miscibility was maximized with 1% by weight of hydroquinone. Blending of doped polyaniline with dodecylbenzenesulphonic acid (PAni.DBSA) in poly (methyl methacrylate) (PMMA) was explained by a change in the conformation of the polymeric chains leading to an increase in the conductivity. The electrical conductivity increased as the weight percent of PAni.DBSA increased, showing a percolation threshold as low as 3.0% by weight and the highest conductivity was achieved at 20% by wt of PAni.DBSA. Scanning electron micrographs showed lowest level of phase separation. Raman spectroscopy is used to characterize the blending process of two polymers aiming to understand the transformations in different types of charged segments. Raman results give complementary data about the blending process showing that together with the structural change of the polymeric chains, there is also a chemical transformation of these polymers. Analysis of Raman spectra was done investigating the relative intensities of the bands at 574 cm⁻¹ and 607 cm⁻¹. A relationship between conductivity and Raman was also proposed. Copyright © 2009 John Wiley & Sons, Ltd.     

Conductivity, dielectric behaviour and thermal stability studies of lithium ion dissociation in poly(methyl methacrylate)-based gel polymer electrolytes

Thin films of poly(methyl methacrylate) (PMMA) with lithium triflate (LiCF₃SO₃) were prepared by using the solution-casting method with PMMA as the host polymer. Ionic conductivity and dielectric measurements were carried out on these films. The highest conductivity for polymer electrolyte with a ratio of 65:35 was found to be 9.88 × 10⁻⁵ S cm⁻¹, which is suitable for the production of mobile phone battery. Thermal gravimetric analysis was carried out to evaluate the thermal stability of the polymer electrolyte. The addition of salts will increase thermal stability of the polymer electrolyte.     

Enhancement of photochemical response in bulk poly(methyl methacrylate) photopolymer dispersed organometallic compound

The enhancement of photochemical response is investigated in Zinc methylacrylate organometallic compound and phenathrenequinone doped poly(methyl methacrylate) photopolymer experimentally and theoretically. In experiments, the improvement in photosensitivity due to ZnMA compound is presented quantitatively. The dynamics parameters, quantum yield and initiation rate of PQ molecules, are determined by nonlinear fitting the experimental curves. The theoretical model with nonlocal effect is proposed to explain the contribution of actual chemical process to the enhancement of photochemical response. The comparison of theoretical and experimental results is finally described. Two significant roles of ZnMA compound, as a catalyst to accelerate the photochemical reaction and as a reactant to participate in the photoattachment with PQ molecules, are demonstrated quantitatively. The time constant of grating formation 20.9 s and the photosensitivity 2.3×10⁻⁵ cm²/J are experimentally obtained in an optimized 0.1 wt% ZnMA doped PQ-PMMA sample. This study contributes the physical mechanism for improvement of photosensitivity and provides significant theoretical foundation for advance the properties of materials in holographic memory.     

Electrochemical studies on polymer electrolytes based on poly(methyl methacrylate)-grafted natural rubber for lithium polymer battery

MG30 is natural rubber grafted with 30% poly(methyl methacrylate). Gel polymer electrolytes containing MG30–LiCF₃SO₃–X (X = propylene carbonate, ethylene carbonate) are prepared by solution casting technique. The polymer–salt complexes were investigated using Fourier-transformed infrared. The ionic conductivity of the electrolytes are determined by the ac impedance studies over the temperature range of 303–383 K and is observed to obey the Vogel–Tamman–Fulcher (VTF) rule. The Li⁺ transference number obtained using the Bruce and Vincent method is <0.3. The Li/Li⁺ interface stability is established and the electrolytes were found to be able to withstand a voltage of more than 4.2 V.     

Spectroscopic properties of polycarbonate and poly(methyl methacrylate) blends doped with europium (III) acetylacetonate

Spectroscopic properties of blends formed by bisphenol-A polycarbonate (PC) and poly(methyl methacrylate) (PMMA) doped with Europium (III) acetylacetonate [Eu(acac)₃], have been studied by photoacoustic spectroscopy (PAS) and photoluminescent (PL) spectroscopy. Emission and excitation spectra, excited state decay times, and quantum efficiency have been evaluated as well. PAS studies evidenced chemical interactions between the Europium complex and the PC/PMMA blend, which presented typical percolation threshold behavior regarding the Eu³⁺ content. PL spectra evidenced the photoluminescence of the Eu³⁺ incorporated into the blend. Photoluminescence property enhancement was observed for the composite in comparison with the precursor compound. Optimized emission quantum efficiency was observed for the 60/40 blend doped with 2% and 4% Europium (III) acetylacetonate.     

Luminescent properties of Tb~(3+)-doped poly(methyl methacrylate) fiber

Lanthanide-doped polymers are very attractive, since they can be used for luminescent optical fiber fabrications.This Letter presents the terbium-ions-doped poly(methyl methacrylate) fiber fabrication and spectroscopic characterization. The measured excited state(5D4) lifetime of 0.741 ms confirms that a used organometallic can be used to obtain an intense luminescence in a polymeric fiber. The luminescence spectrum shape modification versus the fiber length is also investigated.     

Waveguides and quasi-waveguides based on pyrromethene 597-doped poly(methyl methacrylate)

The characteristics of amplified spontaneous emission (ASE) from asymmetric planar waveguides and quasi-waveguides consisting of thin films of poly(methyl methacrylate) incorporating lasing dye pyrromethene 597 deposited onto quartz and glass substrates, respectively, are investigated. The variable stripe length and moving constant stripe methods, together with appropriate theoretical expressions which take into account gain saturation and a simple model based on a four-level laser, allow for obtaining the net gain coefficients as a function of pump intensity, losses, pump thresholds for the onset of ASE, effective stimulated emission cross sections, pump saturation intensities, and saturation lengths. Net gain coefficients of up to 84±3 cm⁻¹ at a pump intensity of 404 kW/cm² (28 μJ/pulse) for quasi-waveguides and up to 59±6 cm⁻¹ at a pump intensity of 360 kW/cm² (25 μJ/pulse) for waveguides were obtained, with pump thresholds of 15.7 kW/cm² (1.1 μJ/pulse) and 6.3 kW/cm² (0.43 μJ/pulse), respectively. When waveguides 8 μm thick were irradiated with pulses of 200 kW/cm² at 10 Hz repetition rate, the ASE remained at 79% of its initial value after 1000 pump pulses in the same position of the sample. In quasi-waveguides 10 μm thick, the emission remained at 82% of the initial value under the same conditions.     

Ionic conductivity studies of 49% poly(methyl methacrylate)-grafted natural rubber-based solid polymer electrolytes

The potential of 49% poly(methyl methacrylate)-grafted natural rubber (MG49) as a solid polymer electrolyte film in rechargeable batteries system were explored. The flat, thin, and flexible films were prepared by solution casting technique. The ionic conductivity was investigated by alternating current impedance spectroscopy. The highest conductivity of 2.3 × 10⁻⁷ Scm⁻¹ was obtained at 20wt.% of LiBF₄ salts content, while 4.0 × 10⁻⁸ Scm⁻¹ was obtained at 15wt.% LiClO₄ salts loading. The observation on structure performed by X-ray diffraction shows the highest conductivity appears at amorphous phase.     

The physical and electrochemical properties of poly(vinylidene chloride-co-acrylonitrile)-based polymer electrolytes prepared with different plasticizers

Lithium ion-conducting membranes with poly(ethylene oxide) (PEO)/poly(vinylidene chloride-co-acrylonitrile) (PVdC-co-AN)/lithium perchlorate (LiClO₄) were prepared by solution casting method. Different plasticizers ethylene carbonate (EC), propylene carbonate (PC), gamma butyrolactone (gBL), diethyl carbonate (DEC), dimethyl carbonate (DMC), and dibutyl phthalate (DBP) were complexed with the fixed ratio of PEO/PVdC-co-AN/LiClO₄. The preparation and physical and electrochemical properties of the gel polymer electrolytes have been briefly elucidated in this paper. The maximum ionic conductivity value computed from the ac impedance spectroscopy is found to be 3?×?10^?4 S cm^?1 for the EC-based system. From DBP-based system down to EC-based system, a decrease of crystallinity and an increase of amorphousity are depicted by X-ray diffraction technique, the decrease of band gap energy is picturized through UV–visible analysis, the decrease of glass transition temperature is perceived from differential scanning calorimetry plots, and the reduction of photoluminescence intensity is described through photoluminescence spectroscopy study at an excitation wavelength of 280 nm. Atomic force microscopic images of EC-based polymer electrolyte film show the escalation of micropores. Fourier transform infrared spectroscopy study supports the complex formation and the interaction between the polymers, salt, and plasticizer. The maximum thermal stability is obtained from thermogravimetry/differential thermal analysis, which is found to be 222 °C for the sample complexed with EC. The cyclic voltagram of the sample having a maximum ionic conductivity shows a small redox current at the anode, and cathode and the chemical stability is confirmed by linear sweep voltammetry.     

Ionic conductivity and interfacial resistance of electrospun poly(acrylonitrile)/poly(methyl methacrylate) fibrous membrane-based polymer electrolytes for lithium ion batteries

Electrospun poly(acrylonitrile) fibrous membrane (PAN-EFM) is prepared and enhanced by adding poly(methyl methacrylate)(PMMA) and subsequently minimizing the average diameter of the PAN/PMMA blend fibers. Electrospinning of the 50/50 wt% PAN/PMMA solution is carried out with the aim of the simultaneous presence of both polymers on the fiber surface. Their presence in exterior surface is confirmed using the Fourier transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR) technique next to the leaching of PMMA with acetone. The process parameters are optimized in four stable modes with the average diameter decreasing from 445 to 150 nm. Mechanical strength of the membrane is measured and reported. Comparing the sample electrochemical properties of the EFMs reveals that the addition of PMMA increases ionic conductivity from 1.02 to 3.31 mS cm^?1 and reduces interfacial resistance from ~1000 to ~400?Ω. It is also demonstrated that the ~300-nm reduction in average diameter of the blend fibers increases ionic conductivity from 3.31 to 5.81 mS cm^?1 and reduces interfacial resistance from ~400 to ~200?Ω.     

Laser processing of poly(methyl methacrylate) Lambertian diffusers

Matrix-assisted pulsed laser deposition was used to deposit poly(methyl methacrylate) on silicon wafers and sodium silicate glass slides for the purpose of making optical diffusers. After deposition, the reflectance of the coated substrates was measured as a function of scattering angle. We found that the angular dependence of the reflectance could be described as the sum of two functions. First, a Gaussian describes the specular reflection of the underlying substrate that has been broadened by passage through the film. Second, a cosine function describes the reflectance contribution from the film itself. We found that by increasing the thickness of the deposited film that we could eliminate the specular reflection to obtain Lambertian diffusers. Since we can control the surface roughness by adjusting the ratio of the two matrices in laser processing, this deposition technique offers the possibility of producing a wide range of diffusers of different types.     

IR laser ablation of doped poly(methyl methacrylate)

We investigate the TEA CO₂ laser ablation of films of poly(methyl methacrylate), PMMA, with average M_W 2.5, 120 and 996 kDa doped with photosensitive compounds iodo-naphthalene (NapI) and iodo-phenanthrene (PhenI) by examining the induced morphological and physicochemical modifications. The films casted on CaF₂ substrates were irradiated with a pulsed CO₂ laser (10P(20) line at 10.59 μm) in resonance with vibrational modes of PMMA and of the dopants at fluences up to 6 J/cm². Laser induced fluorescence probing of photoproducts in a pump and probe configuration is carried out at 266 nm. Formation of naphthalene (NapH) and phenanthrene (PhenH) is observed in NapI and PhenI doped PMMA, respectively, with relatively higher yields in high M_W polymer, in similarity with results obtained previously upon irradiation in the UV at 248 nm. Above threshold, formation of photoproducts is nearly complete after 200 ms. As established via optical microscopy, bubbles are formed in the irradiated areas with sizes that depend on polymer M_W and filaments are observed to be ejected out of the irradiated volume in the samples made with high M_W polymer. The implications of these results for the mechanisms of polymer IR laser ablation are discussed and compared with UV range studies.     

High-repetition-rate femtosecond laser micromachining of poly(methyl methacrylate)

Investigations are performed to explore high-repetition-rate femtosecond laser ablation effects on the physical and chemical properties of poly(methyl methacrylate)(PMMA). A scanning electron microscopy(SEM) is used to characterize the morphology change in the laser-ablated regions. The infrared and Raman spectroscopy reveals that the fundamental structure of the PMMA is altered after laser ablation. We demonstrate the cumulative heating is much greater during high-repetition-rate femtosecond laser ablation, supporting a photothermal depolymerization mechanism during the ablation process.     

Configurational-conformational statistics of stereoirregular poly(methyl methacrylate)s

The mean-square radius of gyration of poly(methyl methacrylate) (PMMA) with Bemoullian statistics was theoretically investigated utilizing the method of periodic condition. The dependent curve of the characteristic ratio of mean-square end-to-end distance on periodic microstructure length increases monotonously with the length and goes gradually to its asymptotic value for atactic PMMA chains (P _m = 0.5). Conformational energies E _α ～1.3 kcal mol^?1 and E _β ～-0.6 kcal mol^?1 of the two-state scheme are acceptable, from which the derived meansquare end-to-end distance and mean-square radius of gyration conform to the experimental data. The ratio ?S²?/χ of atactic PMMA (P _m = 0.2) as a function of the degree of polymerization χ first increases with increasing chain length, then passes through a maximum at χ = 30, and finally decreases to its asymptotic value, which is in reasonable agreement with the experimental measurements reported elsewhere. The ratio ?S²?/χ as a function of stereochemical composition indicates that theoretical and experimental data are in accord for isotactic and atactic PMMA, but small-angle neutron scattering (SANS) measurements are higher than the calculated values for syndiotactic PMMA.     

Effects of UV-irradiation on the thermo-mechanical properties of optical grade poly(methyl methacrylate)

We studied the evolution of the thermo-mechanical properties of poly(methyl methacrylate) (PMMA) materials exposed to ultra-violet (UV) light. To do so we measured important mechanical parameters including the fracture strength, the stress-strain relation, and Young's modulus as a function of the UV-irradiation dose. We concluded that the mechanical properties of PMMA are affected by UV light. The ductility disappears and the strength and strain at rupture strongly decrease (over 30%). The evolution of the Young's modulus is discussed as a function of the cross-linking degree of the materials. Moreover we observed the occurrence of surface damage, which in its turn enhances the degradation of these mechanical parameters.