Dear Cihan Baydaroglu, titration may be done by chemical and spectroscopic procedures. There are many operating factors that influence the ionization kinetics, especially in the case of weak acids, such as MW, tacticity, and concentration. Please have a look at the following documents. My Regards

Thank you for the detailed answer.

I've a further question:

How can I calculate the molar mass from the equivalence point.

I found an equation N2V2 = n1V1.

You can not, may be this is possible only if the COOH are end groups, which is not the case for PAA.

Ok, but I found a paper in which the molar mass was calculated by titration data I assume by using the volume at the equivalence point. They didn't mention how. I uploaded the Supporting Information for you.

Would you please send the DOI of your base reference. I couldn't get the right place where chemical titration of PAA is used to obtain MW.

I believe you can detect carboxyl groups by producing a thin film and running FTIR, carboxyl groups have a typical absorbance

Sorry for the late answer. Here is the DOI 10.1016/j.polymer.2017.09.005

The author also calculated the effective molecular weight per charged unit of his hydrophobically modified polymer under the assumption of full deprotonation of his polymer. For this purpose he deprotonated PAA with an execess of 15mol% NaOH. A modification of PAA with 10% Dodecylamin was performed. The authors' calculated value is 98.7 g/ mol. How did the author calculate it?

Due to amination at the carbonyl group of Acrylic Acid OH- is removed so that I substracted it in my calculation.

My first guess was:

M(Acrylic Acid) + 10% x M(Dodecylamin) - 10% M(Oxygen) -10% x M(Hydrogen)

72.06 g/mol + 10% x 185.35 g/mol - 10% x 16 - 10% x 1 =88.895 g/mol

What did I forget in my calculation - maybe the counter ion, because we have the deprotonated form of PAA.

When I add the molar mass of Na+ - 22.9897 u - the value gets higher.

My second guess was:

M(Acrylic Acid) + M(Natrium) + 10% x M(Dodecylamin) - M(Oxygen) = 96.58 g/mol.

This last value is also wrong but closer to the expected value (98.7)

Thanks in advance!

Without looking to the paper, what it may be done is simply to add the mass of the number of substituants per chain macromolecule to the MW PAA (virgin), which is already known. Titration determines the number of lost acid groups after substitution, i.e., COOH concerts to COOR. This is how the new MW is determined. Once I check the paper, may be I will add further information.

NB. Are you sure that the amine reacted with the carbonyl group?

Yes, this is the main reaction of this synthesis. Yeah this is also my assumption and how I tried to calculate it.

I think the substitution reaction with the amine took place at the hydrogen (proton) of COOH and not on the carbonyl CO group. Please take a look at the following paper.

https://doi.org/10.1002/pola.21042