NMR is suitable for examining the molecular structure and interactions in your hydrogel film, while XPS provides valuable surface-level chemical bonding information. XRD may yield only a broad halo pattern due to the hydrogel's amorphous nature, so consider additional techniques like FTIR and SEM for a comprehensive analysis.

Thank you for your valuable insights. I have a couple of follow-up questions. Since the hydrogel contains plant extract, would the XRD results be more meaningful, considering that the chemical properties of the hydrogel may change? Additionally, the gel is not fully soluble in water, chloroform or DMSO, would it still be possible to conduct NMR? If so, would it be more appropriate to perform 13C-NMR or 1H-NMR? I also plan to carry out FTIR, SEM, TGA, and DSC analyses.

Thank you again for your help!

Just a remark, except for XRD and IR none of these methods is "in situ", i.e. you always require such a lot of sample preparation (dissolution plus maybe separation; or high vacuum; or sectioning/cutting) that I would doubt that the results are relevant to characterize an "operational" hydrogel. Btw, in XRD you expect more or less no signal (amorphous), and IR will give you an incredibly dense forest of bands, overlapped by huge water absorption.

I would first read reviews, maybe there are some that are specialized in hydrogel analysis, before applying expensive and time-consuming methods (XPS!).