Dear Leila Sohrabi-Kashani, the simplest way to know MW is to ask the supplier. If you want to find it by yourself, viscometry is the technique customerly used, but since you mentioned it is electrospinnable, then MALDI-TOF may be also used. There are various other techniques, it depends on their availability at your place of work. My Regards

Abdelkader BOUAZIZ thanks for your kind reply. unfortunately, I don't have any information about the supplier. could you please send the links to the related references?

You can find references by simple search. These are examples:

http://dx.doi.org/10.13005/msri/070214

https://doi.org/10.1163/156856106778456636

May be you can access the following presentation:

https://www.slideshare.net/PRAVINSINGARE/determination-of-the-molecular-weight-of-high-polyvinyl-alcohol-pva-by-viscosity-method

Molecular weight of Polyvinyl alcohal= 1,15000

Leila Sohrabi-Kashani normally molecular weight is written on the company bottles if not you can also find MSDS file on internet.

For PVA electrospinning following video may be helpful:

https://www.youtube.com/watch?v=3TmuMAkOaDs