Synthesis Of PVDF-g-PSSA Proton Exchange Membrane By Atom Transfer Radical Polymeriaztion

PEMFC is a new type of generator, which promising power generation with high efficiency and low environmental impact, so a lot of reseachers focus on this project. Ion exchange membrane, as the most important part of a PEMFC, plays a key role of proton conduction. Its performance will affect the overrall property of PEMFC direcly. Nafion membrane is a perflourinated ionomeric membrane, with its high proton conductivity and stability, shares a great part of membrane market presently, but the complex preparation technology and low methanol permeability inhibit its development. In this paper, in order to obtain Ion exchange membrane, we take PVDF as a basic body, graft sulfonic acid groups on it by using ATRP technique. And their characteristics have been tested by FI-IR, TGA and so on.At this experiment, the membranes are prepared by two different methods. The first one, styrene monomers graft onto PVDF main chain at first, then sulfonate them later on. The second one, sulfonic acid groups have been grafted onto PVDF directly.By the first method, we discussed grafting conditions. The results showed that the grafting degree of styrene raised with the increase of the amount of catalyst, but too much catalyst brings a problem of purification, which can cause a large lost of our product. When the catalyst dosage is0.1g, the grafting ratio is26%. Grafting degree increased by taking longer reaction time, but after12h, it changed little. Grafting degree also increased by rising reaction temperature. We used two methods to sulfonate of PVDF-g-PS, film sulfonation and solution sulfonation. The results showed that film sulfonation is better than solution sulfonation. The mechanical strength of grafted membrane is lower than that of pure PVDF membrane, and also downward of thermal stability.On the basis of successfully grafting styrene onto PVDF by ATRP, we use a second kind of monomer to obtain ion exchange membrane. Since this type of monomer has been sulfonated already, we can skip the sulfonation step, and tests show a better result than the previous one, which proton conductivity reached4.91×10-4S/cm, nearly one order of magnitude higher. Because the molecular chain structure is almost the same with the previous, so the mechanical properties and thermal stability of this membrane are nearly the same with the previous one.Cause its out first attempt to obtain proton exchange membrane by ATRP, and in PVDF, C-F bond is very low active, so grafting degree is not high. So that the performance of the film is not good enough, which needs more further study.