Having NMR you can calculate number average molecular weight.

Maybe try some MS techniques (MALDI or ESI if molecular weight isn't big)?

There is also viscosimetric method based on viscosity of the polymer solution.

Static light scattering method could also help.

Having NMR you can calculate number average molecular weight.

Maybe try some MS techniques (MALDI or ESI if molecular weight isn't big)?

There is also viscosimetric method based on viscosity of the polymer solution.

Static light scattering method could also help.

Do you have Rheology? if yes, you can do the frequency sweep measurement on the Parallel Plate Rheometer where you will get the viscoelastic response of your polymer melt thereby zero shear viscosity, crossover modulus and Polydispersity index. The zero shear viscosity is directly proportional to the molecular weight of the polymer. From the value of zero shear viscosity, using  the appropriate model, you can be able to determine the molecular weight  of the polymer. I hope this helps!!

I would also suggest viscometry in solution if you know the solvent for your polymer.

The following reference describes not only GPC but also viscometry in solution:

https://www.researchgate.net/file.PostFileLoader.html?id=57651ff4615e27d2fd15a5b4&assetKey=AS%3A374273265946625%401466245108249.

NMR based on end-group estimation is not very precise and works for low molecular weight only.

You may consider also osmometryhttp://willson.cm.utexas.edu/Teaching/Chem367L392N/Files/Membrane%20Osmometry.pdf

http://www.dtic.mil/dtic/tr/fulltext/u2/487755.pdf

Although it requires a test equipment.

The following file compares various methods:

http://yjsb.ciac.jl.cn/uploadfile/20100420065821860.doc.

the following paper details the use of NMR to analyse MWt.

What type of polymer do you want the MW of?

If the sample is oligomeric, it  is possible to separate the sample iusing hplc and then calculate the distribution moments using traditional math.

If you have no equipment, relative viscosity determination via careful experimentation can be the most generally informative. 

if you have one of the Zetasizer nano series instrument, then you can measure the molecular weight of your polymer easily by dispersing them in some solution. This instrument uses the principle of static light scattering.

Thanks

Dynamic light scattering provides only a valuse based on the Z average translational diffusion coefficient. The results can be quite misinforming in all but the simplest cases.

I would also suggest a measuring of viscosity in suitable solvent ( if you know the solvent for your polymer). And I can help you in that.