Hi Yusof

A polymer’s molecular weight is related to that of the monomer, and the number of monomers present in the polymer molecule. The molecular weight of styrene is 104 Da. Hence, the molecular weight of polystyrene is 104n, where “n” is the styrene molecule number in the polymer chain. Both the distribution shape and the average MW influence the properties of a polymer. Therefore, measuring MW requires measuring the MW of individual chains and the number of chains of any specific weight.

The different methods used for measuring MW are:

End group analysis

Membrane osmometry

Viscometry

Light scattering

Molecular size, similarly to MW, is a defining property of most polymers. A polymer molecule’s size in solution directly impacts its rheological behavior, which is linked directly to formulation performance.

MW and molecular size relationship is not constant, and different polymers show different molecular densities in solution.

Most polymer molecules are below 100 nm, and hence, the requirement for size information calls for techniques that have the ability to measure nanoparticles. Three different techniques are applied: dynamic light scattering (DLS); MALS; and SLS in combination with intrinsic viscosity (IV) measurement.

Molecular wt of a formulated nanoparticle will not be changed !

You maybe asking about the wt of the individual nanoparticle ? If it is true ?

You can mesure it using TEM

try to read the following article it will help you a lot

http://pubs.acs.org/doi/abs/10.1021/ac049307x?journalCode=ancham

Muhammad and Ahmad, thank you for answering;

The article you suggested in your link, studied molecule weight not the weight average molecular weight.

Kinetically speaking as the polymerization reaction occurred, the weight average molecular weight will change through crosslinking/grafting and chain scissoning/degradation.

I hope to get more views from more scientists.