Dynamic light scattering is also acceptable, either alone or coupled with chromatography (GPC or SEC) or Field Flow Fractionation.

Membrane osmometry and viscosimetry may be the answer, we've tried both quite satisfactorily with several allowances in different systems. Though these approaches are based on total colligative properties of solution and will give one efficient value of MW not allowing to distinguish between components in a mixture of polymers, if you have one. SEC (or GPC) looks preferable due to its ability to achieve real (or apparent) MW distribution.

Thank you for the guidance Dr. Cote and Dr. Igor. Does these technique will have any impact on the quality of paper published. Like say If I quote the MW by these technique and by GPC, editor will prefer which one or both will get equal weightage.

If I were reviewing the paper, I would prefer the more complete information given by light scattering.

If this were a matter of polymer identification via MW, all these methods are about equal. By publication number rheology and light scattering of polymers do prevail over osmometry, so it wold be easier to find references. Though for me personally this fact would only make osmometric measurements the more interesting. Have a nice try.

Thank you Dr Cote and Dr. Igor, for your replies, and I try to follow your suggestions.

Sedimentation equilibrium in the analytical ultracentrifuge is probably the gold standard for measuring molecular weights.  Be careful osmometry measures number average molecular weight and viscometry measures viscosity average molecular weight and I think to get molecular weight from DLS there is an assumption on the shape of the polymer. Field Flow Fraction is also an excellent method when coupled to MALS detection. 

The question of which method to use depends on the sample (homopolymer, copolymer, polyelectrolyte etc) and the expected molar mass .

LS of copolymers is quite compliceted if heterogeneous polymers (copolymers, blends) are involed. In addition LS is more suited for higher molar masses.

NMR (end Group Determination) is suited if you have well defined end groups and the olar mass is not too high.

Collgative properties (osmomety, mebrane or vapor pressure) is also suited at medium or lower molar masses, respectively.

Viscosity molar mass can be derived if MH patamters are available from literature.

Finally it remains the question whether a true molar mass is required or a relative molar mass is sufficient.

Thus the question has to be stated mote precise.

Thank you Dr. Morris and Dr. Radke. Sir I have synthesized Block copolymers via ATRP and in most of the literature GPC and SEC has been performed but currently I do not have access to that. It was the main reason for asking this question, would I be able to publish a good publication with the mol wt data from other techniques instead of GPC or SEC.