I have synthesized PEG coated nanoparticles for which I need to calculate the grafting density of the polymer. I have learned that majority of publications calculate it by using TGA. Can you tell me how grafting density is calculated from the TGA plot? It will be great if you can suggest any other method to calculate the grafting density. Can FTIR be used for calculating grafting density? If yes, how?
to calculate the grafting density of the polymer depends on the percentage used for the grafted material to the polymer and the conditions of the experiment, the material loaded if they contain an effective group can be calculated by spectral or analytical methods
I would suggest to use TGA under O2 atmosphere. The difference in the mass loss between the bare nanoparticle and the modified nanoparticles will give the grafted polymer amount.
Besides, elemental analysis (CHNSO) could be used as well.
TGA and CHNSO analyses can be used when the core nanoparticle is an inorganic material or incombustible!
FYI, FTIR is commonly used for qualitative analysis of a sample, even though it can be calibrated for quantitative analysis as well.
@ Kashmiri Deka, the unit is mg.
You should have the initial amount of the sample submitted to TGA!
As there could be weight loss for the bare inorganic nanoparticle, calculated the weight loss as following:
mb,0= Initial mass of bare nanoparticle
mb,1= Final mass of bare nanoparticle at high temperature in TGA
weight loss of bare nanoparticle:
Mb= mb,0 - mb,1
mb,1 = (final weight loss%)*(mb,0)
Then:
mm,0= Initial mass of modified nanoparticle
mm,1= Final mass of bare nanoparticle at high temperature in TGA
weight loss of modified nanoparticle:
Mm=mm,0 - mm,1
mm,1 = (final weight loss%)*(mm,0)
mass of the graft:
Mg=Mm - Mb
Ali Nematollahzadeh Thank you so much! Can you mention a publication where they have shown the grafting amount only in gram instead of presenting in terms of grafting density in chains/nm2?
The simplest way is using TGA. It will work if the heat stability of the nanoparticles is much better than that of the grafted polymer. The common unit is mg.
@ Kashmiri Deka , having the mass of the graft in hand, you can use the molecular weight of PEG, Avogadro's number, and surface area of the nanoparticles to convert the mass into chains/nm2
For more information please see the following paper:
Article Measuring the Grafting Density of Nanoparticles in Solution ...
Article Molecularly imprinted polydopamine nano-layer on the pore su...
In addition to the really useful TGA, sometimes it is possible to thoroughly collect after the treatment all the coated nanoparticles and to compare their weight with the bare ones loaded in the reaction mixture before the coating (in your case PEO).
Ali Nematollahzadeh I have two more questions..... Do I have to take equal amounts of modified and bare nanoparticles for TGA experiment? Secondly, should the final value of mass of grafted polymer (Mg) be divided by initial amount of grafted sample taken for TGA and thus express the amount of graft per unit mass (g or mg) of the sample?
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