Moreover, it is interesting to note that the S-PVdF exhibits 33% of DS upon sulfonation for the Kainic acid of 2 h, whereas the DS value is reported to be 32% for S-PVdF-co-HFP at 7 h of period of sulfonation. From the above analysis, one can judge that the rate of sulfonation of PVdF is higher than that for PVdF-co-HFP at the same temperature. Nevertheless, amongst the sulfonated samples, the maximum DS is exhibited by the sample SP-2, which is expected be for more suitable as a PEM in DMFC. Therefore SP-2 is utilized for further studies in this article.
3.2. Analysis of XRD
Fig. 5. XRD patterns of pure and sulfonated PVdF.Figure optionsDownload full-size imageDownload as PowerPoint slide
The calculated value of crystallinity for different samples is plotted as a bar diagram in Fig. 4. From the figure, intracellular route is observed that the crystallinity (%) of the PEM decreases with an increase in the duration of sulfonation. This is expected as increasing sulphonation disrupts regular structure and thereby diminish the crystalline regions .