. . . "PPO), vinyl polymers, such as polyvinyl alcohol (PVA), polyethylene sulphonic acid (PESA), polyvinylamine (PVAm), polyvinyl-pyrrolidone (PVP), poly-4-vinyl pyridine (P4VP), cellulose derivatives, such as methyl cellulose (MC), ethyl-cellulose (EC), hydroxyethyl cellulose (HEC), carboxymethyl cellulose (CMC), polysaccharides, such as acacia, agar and agarose, heparin, guar gum, xanthan gum, and pro" .