you can use ionic interchange resin or dialysis 

Dear Tb Bo,

You can try dissolving your polymer in water at appropriate concentration and put it inside a membrane dialysis bags (membrane cut off (pore size) to be used will depends on the Mw of your polymer). if your polymer is high Mw you can use 10-30-50 kDa COff membranes and for low Mw polymer you can use 1000-3000 Da Coff membranes. Then put the membrane bag containing your dissolved mixture in a recipe with distilled water and stir the water for speed the osmosis process. Change the water several times in the day and 2-3 days will be enough for having your polymer free of NaOH. You can also use dialysis devices commercially available.

Another approach is to prepare a concentrate polymer solution (3-5% w/v), adjusting pH to 7 with HCl (at slightly lower concentration than NaOH used in your synthesis)  and then precipitate it with a non solvent solution (e.g. acetone), Typically adding 5 volume of non solvents per 1 volume of solution.  Then centrifuged the solid and  washed with ethanol mixtures (70, 80, 90 % v/v) . The number of washes will depends on the amount of Chloride ions that will remains after  each washing  step and that can be monitoring adding a drop of AgNO3 to the solution . Finally , absolute ethanol is added to the solid washed and then dried at room temperature. 

The third option is to use a cationic exchange resin and put it in contact with a polymer solution because you want to remove the Na+ ion mainly.

Hope it could help you,

Best regards,

Gustavo

Dear Tb Bo,

I agree with the answer that suggested by Dr. Edwin A. Murillo

Good luck

Dear Gustavo Cabrera

if i have a cross-linked polymer, can i remove salt by using dialysis bags?