you might calculate the wight of the deposited polymer from the polymerization charge using Faraday law
Wight (gm) = [polymerization charge (C) x moleclare wight of monomer]/[no. of electrons transfer X 96500]
It is actually not quite that simple because the polymer is deposited in a slightly over oxidized form. And the degree of over oxidation / doping will be dependent on the exact way you make the deposition.
One way to approach this problem is to do your polymerization and count the charge used (Q.p). Then reduce the polymer to its neutral form and count the charge used for that (Q.r). The difference, Q.p - Q.r is the charge you should use in Gabers formula above. If you can argue that you deposited polymer has a long chain length, the number of electrons used per monomer will be 2 for most conducting polymers.
In reality the method above only works if you do not oxidize electrolyte components during deposition, and more critical: you do not reduce dissolved oxygen during determination of Q.r. It requires very careful experimental design to ensure that these conditions are met.
you can calculate the wight of the deposited polymer from voltammogram peak current or from Electrochemical Quartz Crystal Microbalance experiments.
This question has not an absolutely correct answer, or at least a simple one, as Keld stated.
The main problem is that the charge passed during electro-polymerisation includes a fraction for oxidation of the deposited polymer. Keld's suggestion to fully reduce the polymer to obtain the charge used for oxidation of the polymer is logical, but it is practically not always reliable. This is because the potential for electro-polymerisation is usually significantly higher than that for oxidation of the deposited polymer. Consequently, over-oxidation of some of the deposited polymer is inevitable, and this part of charge is not recoverable.
Shen-Ming's suggestion of using EQCM is helpful, but the measured mass would have always involved doping ions (sometime in pairs) and solvent molecules. Also, because the deposited polymer is not strictly rigid, it casts some uncertainty on the EQCM measured mass.
The experimentally reliable, but theoretically not fully accountable method is to deposit the polymer on a thin platinum wire (
use EQCM
other methods may result in erroneous values as conducting polymer will storgae charges
Dear Profs. Thank you for all your valuable answers/ sugesstions....but still I confused that ,
1.How I can measure the charge from CV. Whether I use only the redox peaks ? Because for PANI a nemurous redox peaks were appeard depending on the potential window. Herewith I attached a CV of PANI deposited on GC. Can any one help to findout the polymer loading.
Integration of the current between two potentials which should be as wide as the whole potential range for recording the CV. However, this CV shown here is the CV of the deposited polymer, not that for polymerisation. To obtain the charge of polymerisation, you need record the CVs for that. However, it is more convenient to carry out polymerisation under potentiostatic or galvanostatic control which will make it easier to obtain the polymerisation charge.
If I were you... I simply weight the electrode before and after deposition.
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