Folks, I am looking for low MW (<20 kD) sodium polystyrene sulfonate (PSS) for coating nanoparticles. The widely availble molecular weight is 70 kD, but with this molecular weight, dialysis cannot be used for purification. The ideal MW should be less than 20 kD. I know about the suppliers of GPC standards, but these standerds are too expensive ($300 per gram), besides, we do not need highly monodisperse polymer. Ideally, we would like to simply buy it and not synthesize it as we do not have characterization capabilites. I will appreciate any suggestions. Thanks.