I have attached an epoxy with a nanofiller material in presence of a solvent and have microencapsulated it. The shell material is Urea-Formaldehyde.Now I am facing difficulty to prove that the core materials have actually been encapsulated successfully. I have studied SEM,TEM, optical microscopy but nothing seems to confirm the core materials convincingly.
You can resolve your microcapsule in the primary solvent and after they're completely degraded, elute the solution in HPLC (High Performance Liquid Chromatography) column and set it at the desired wave length. Then look for the absorbance peak at the encapsulant MW in the resulted spectrum. This is the most reliable and widely used technique.
You can use confocal microscopy for this. We used it in our study, you can check the images: https://www.researchgate.net/publication/252324937_Robust_molecular_micro-capsules_for_encapsulating_and_releasing_hydrophilic_contents
Article Robust molecular micro-capsules for encapsulating and releas...
Dear all;
I think ellipsometry and XRD may be very useful in this situation. Regards
you can prove by tagging the starting materials with FITC molecules followed by taking confocal microscopy images.
How big are the capsules? What is in the core? I don't think SEM and optical will help. For TEM you will need good contrast between the core and the shell. So if you have metallic particles, TEM will work. If you have polymeric particles encapsulated, it won't.
If the degradation temperature of the core and the shell are vastly different, you can use TGA, but that won't prove core-shell structure, just that you have two components.
It depends on what exactly is your nanofiller. If it is or part of it's UV/VIS active, you can subject the capsules to be broken mechanically and get the UV/VIS spectrum to see the active ingredient. Or the FTIR technique to identify the specific peaks of the filler if you can get capsules in mg levels.
I think that you can use infrared spectroscopy and DSC analysis. The profile of the particles encapsulated is different of the urea or formaldehyde.
If you have a different contrast beetween core and shell you can make Small Angle X-Ray scattering, and notice the difference before and after the encapsulation.
You can cut the microcapsules and observe the cross-section morphology using SEM. Another method is using the FTIR through breaking the capsules.
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