Dear Nizar

In my opinion, the best way to determine the molecular weight of a polymer is GPC (gel permeation chromatography). In most cases, you use polystyrene standards to do a calibration curve (elution time vs. molecular weight (or, more precisely, "molecular size"). For that reason, you won´t have a real value of molecular weight but with respect to polystyrene. Some GPCs now, apart from the refractive index detector, have other detectors (light scattering, viscosimeter, etc.). In these cases, you can elucidate the real molecular weight of your polymer.

I hope it helps,

Aitor 

Light scattering would be another technique

Take a look at the textbook by Hiemenz: Principles of Colloid and Surface Chemistry

This is a very interesting question

بامكاني ان استخدم من الافضل لحساب الوزن الجزيئي للبوليمرGPC 

I think that is GPC / SEC is the  best method because it is the only technique that measures Mn, Mw, Mz and Mz+1 at the same time by

measuring the entire distribution of the polymer. SEC also allows another average

molecular weight to be calculated, the peak molecular weight Mp, defined as:

Mp = molecular weight of the highest peak

Therefore, Mp is the mode of the molecular weight distribution. Mp is quoted for very

narrowly distributed polymers, such as polymer standards used in calibrations.

you can by use (gel permeation chromatograpy)

  in addition to the expense of viscosity to calculat Molecular weight can be calculated by measuring the scattering of light  and Another technique is through osmotic pressure  accounted

Dr,

You can measure the molecular weight of polymer by using Gpc,scattering of light ,scattering of light .....

There are different methods used for measuring MW are:

End group analysis

Membrane osmometry

Viscometry

Light scattering

 although you can see

http://www.azom.com/article.aspx?ArticleID=12255

in addition to the expense of viscosity to calculat Molecular weight can be calculated by measuring the scattering of light and Another technique is through osmotic pressure accounted