الفهرس 
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Abstract
The development of cheap and efficient proton conducting polymers has attracted the attention of scientists, leading to their importance in applications of direct methanol fuel cells. Modifying cellulose acetate with graft copolymerization improves its properties, allowing it to be used in fuel cell applications.This thesis is divided into four major chapters:Chapter one: Introduction, which focuses on providing a quick overview of the fuel cellsChapter two: Discusses the history and varieties of fuel cells, the operation of direct methanol fuel cells (DMFCs), and the polymer electrolyte membranes used in DMFCs.Chapter three: Describes materials, experimental procedures and techniques used in the processes of preparation, characterisation, and evaluation.Chapter four: Result and discussion, presenting the obtained results as followPart 1: Preparation and characterization of cellulose acetate (CA), poly(sodium 4-styrenesulfonate) (PNaSSA) and cellulose acetate -g-poly(sodium 4-styrenesulfonate) (CA-g-P(NaSSAPart 2: Investigating the variables that influence the grafting proces Part 3: Evaluation of grafted membranes for DMFC applications.This study aimed to develop novel cellulose acetate-based acetate based thin-film membranes using free radical polymerization as a method to protonate and modify CA for use as PEM1. Grafted membranes (CA-g-P(NaSSA)) were prepared and characterized using various techniques, including FT-IR spectroscopy, TGA/DSC, H-NMR, XRD, SEM, and EDX to provide evidence for the occurrence of grafting polymerization2. The effect of grafting conditions such as CA, initiator, monomer concentration, reaction time, and temperature on grafting parameters such as grafting efficiency (GE%), grafting yield (GY%), and add-on (%) was investigated.3. Finally, the effect of grafting processes on fuel cell properties including; water and methanol uptake, dimension stability, wettability, ion exchange capacity (IEC), thermal oxidation stability, methanol permeability, optical properties, and finally membrane efficiency were also exploredThe study discovered the following results The maximum grafting parameters i.e., grafting efficiency (95%), grafting yield (81%) and add-on (45%) were obtained with a reaction time of 3 hours, a reaction temperature of 60 °C, CA concentration of 10%, 0.277 mM KPS, and 1.5 g/L NaSSA monomer When the add-on (%) is increased from 8.0 to 45 %, the water uptake values increased from 17.73 to 31.45%. As a result, the IEC reach its maximum value of 2.79 (meq/g) at an add-on percentage of 45%. All grafted membranes exhibit excellent thermal oxidative stability at elevated temperatures (up to 80 °C) and thermal stability as determined by TGA results The grafted membrane has a methanol permeability of 5.514 10-7 cm2/S, compared to 85.9 10-7 and 24.9 10-7 in the case of CA and Nafion® 212 membranes, respectivelyThe developed membrane’s proton conductivity was found to be superior to that of the pristine CA membrane and increased with increasing graft PNaSSA add-on (%) up to 45% to reach maximum value (4.77×10-3 S.cm-1) at the ambient temperature compared with the pristine CA membrane (0.035×10-3 S.cm-1).These previous results indicate that the CA-g-PNaSSA membrane exhibited superior characteristics, making it a great alternative for the high-cost commercial Nafion® 212 membrane in DMFC applications.