Synthesis of amphiphilic graft copolymer via click chemistry

The proton exchange membrane fuel cell (PEMFC) that is also known as polymer electrolyte membrane fuel cell uses a acidic and water-base polymer membrane as electrolyte with Pt electrodes. Operating temperatures of PEMFCs are below 100 oC and it can be adapted electrical output with dynamic power demands. These cells must be worked with pure hydrogen since it needs relatively low temperatures and costly metal based electrodes. Nowadays, PEMFCs are used in industry in widening scale, but mostly used in light duty vehicles, material handling vehicles, etc. The issues like chemical degradation at elevated temperatures, poor ionic conductivities at low water content and high cost, restrict the commercial proton exchange membranes. Therefore, alternative membrane researches for fuel cells maintain timeliness. During the last decades, chemical resistance, weathering elements and oxidants, low surface energy properties and hydrophobic properties make the fluoropolymers interesting for fuel cell membranes. Especially amphiphilic fluorinated graft copolymers have a great importance for PEMFC applications. P(VDF-co-CTFE) is one of the fluoropolymer that can be used in this applications due to its excellent properties such as chemical resistance and conductivity. As a result of this, a lot of reasearch have been reported to obtain alternative fuel cell membranes. Atom transfer radical polymerization (ATRP) is a controlled free radical polymerization technique. Well-defined amphiphilic graft copolymers with controlled molecular weight, well-dispersed macromolecules, terminal functionalities and chain architectures can be achieved in a polymer via this method. Also, ATRP permits to synthesize advanceed fluorinated polymers. Click chemistry is one of the methods to unite molecules quickly. High yielded, stereospecific, modular products can be obtained easily with this method. Recently, there are several progress have been identified such as copper(I)-catalyzed azide alkyne reaction and this technique have huge concern for polymer chemist. In this study, P(VDF-co-CTFE) was selected for the main chain and tried to synthesize a suitable molecule for PEMFC. Firstly, some ionic molecules are tried such as 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS), 2-acrylamido-2-methyl-1-propanesulfonic acid triethylamine salt (AMPS-TEA) and 3-sulfopropyl methacrylate potassium salt (SPMAK) to obtain grafted fluorinated copolymers, but covalent bonding did not observed. So, methyl methacrylate (MMA) and tert-butyl acrylate (tBA) are used to understand the reactivity of P(VDF-co-CTFE) on hand. As a result of these studies, PtBA was selected as pendant group. Then the PtBA was grafted from azidated P(VDF-co-CTFE) with click chemistry method. The resulted polymers were characterized with FT-IR, 1H-NMR, DSC and GPC instruments. Also, electrochemical impedance measurements and contact angle analysis were investigated.