A. Lepit

Effects of lithium salt on chitosan-g-PMMA based polymer electrolytes

Abstract A grafted copolymer [chitosan-g-poly(methyl methacrylate) (PMMA)] was prepared via gamma irradiation induced graft polymerisation technique. The degree of grafting (DG) increased with increasing absorption dose. The change of structure in the chitosan backbone upon methyl methacrylate grafting was monitored by Fourier transform infrared spectroscopic analysis. Differential scanning calorimetry was carried out to examine the reduction in crystallinity of chitosan due to the branching effects of PMMA segments on chitosan. Differential scanning calorimetry trace of chitosan-g-PMMA has a glass transition temperature Tg at 110°C. Thermal gravimetric analysis was used to evaluate the thermal stability. Polymer electrolytes based on chitosan-g-PMMA were then prepared by doping lithium triflate into the grafted solution. These grafted polymers containing different amounts of salts were investigated as possible ionic conducting polymers. The ionic conductivity of the electrolytes was determined at various DGs. The conductivity of the electrolytes was found to increase with the increase in DG. The highest ionic conductivity of chitosan-g-PMMA–LiTf was 4·05×10−5 S cm−1 for the film containing 60·0 wt-% LiTf.

Seeded Porous Silicon Preparation as a Substrate in the Growth of ZnO Nanostructures

In this work, seeded porous silicon (PSi) was used as a substrate in the growth of ZnO nanostructures. PSi was prepared by electrochemical etching method. ZnO thin films as seeded were deposited via sol-gel spin coating method. ZnO nanostructures were grown on seeded PSi using hydrothermal immersion method. In order to study the effect of post-heat treatment on the substrate, post annealing temperature were varied in the range of 300 to 700 °C. The FESEM results shows ZnO thin film composed of nanoparticles were distributed over the PSi surface. Based on AFM characterization, the smoothest surface was produced at post annealing temperature of 500 °C. There are two different peaks appeared in PL characterization. The peak in near-UV range is belonging to ZnO thin films while a broad peak in visible range can be attributed to ZnO defects and PSi surface. In addition, FESEM, XRD and PL were used to characterize the ZnO nanostructures. The FESEM results revealed ZnO nano-flower were successfully grown on seeded PSi. Hexagonal wurtzite of ZnO with dominated by the plane (100), (002), and (101) was found by XRD characterization. Two different peaks in UV range and visible range can be attributed to ZnO nano-flower and various defects of ZnO, respectively.

Preparation and characterization of polymer blend based on sulfonated poly (ether ether ketone) and polyetherimide (SPEEK/PEI) as proton exchange membranes for fuel cells

Blends of sulfonated poly (ether ether ketone) (SPEEK) and polyetherimide (PEI) were prepared in five different weight ratios using N-methyl-2-pyrrolidone (NMP) as solvent by the solution cast technique. The degree of sulfonation (DS) of the sulfonated PEEK was determined from deuterated dimethyl sulfoxide (DMSO-d6) solution of the purified polymer using 1H NMR method. The properties studied in the present investigation includes conductivity, water uptake, thermal stability and structure analysis of pure SPEEK as well as SPEEK-PEI polymer blend membranes. The experimental results show that the conductivity of the membranes increased with increase in temperature from 30 to 80°C, except for that of pure SPEEK membrane which increased with temperature from 30 to 60°C while its conductivity decreased with increasing temperature from 60 to 80°C. The conductivity of 70wt.%SPEEK-30wt.%PEI blend membrane at 80% relative humidity (RH) is found to be 1.361 × 10−3 Scm−1 at 30°C and 3.383 × 10−3 Scm−1 at 80°C respect...

Graft Copolymerazation of 1-Vinylimidazole onto Poly(vinylidene Flouride) by Radiation-Induced Grafting for Fuel Cells Membrane

γγψγRadiation-Induced grafting of high energy γ-rays onto proton conducting polymer electrolyte membranes (PEMs)-based poly(vinylidene flouride) (PVDF) immersed in 1-Vinylimidazole (VIm) solution have been studied. The different concentrations of VIm from 0.5 to 3.0 M in 1,4-dioxane were prepared. The samples were then exposed to γ-rays from 20 to 100 kGy. The properties of the membranes were characterized based on degree of grafting, spectroscopic study, surface morphology, and X-ray diffraction (XRD) measurement. The degree of grafting (DoG) increased in the PVDF membrane associated with absorbed dose. The results showed that the surface morphology of the membrane observed homogenous when grafting with VIm the after irradiation that compliment with XRD study.

Effects of UV irradiation time on electrical, physical and thermal properties of SPEEK–CS composite membranes

Abstract A series of cross-linked composite sulphonated poly(ether ether ketone) (SPEEK) proton exchange membranes were prepared. A mixture of SPEEK–chitosan (SPEEK–CS) membrane was prepared by dissolving SPEEK in dimethyl sulphoxide and CS in acetic acid. The homogen formed was later irradiated with an ultraviolet (UV) source to induce cross-linking. The time of UV irradiation has been found to influence the performance of the membrane’s conducting properties. The composite membranes are prepared through the general formula of SPEEKxCS(1−x), where x = 0·3. The cross-linked membrane with an irradiation time of 120 min of 300 W UV is found to achieve the highest proton conductivity values. In addition, the water uptake behaviour is also found to be proportional to its proton conductivity. All the membranes lost an average of 10 mass-% at the temperature of ∼240°C.