Preparation of Amphoteric PVA Hydrogel

First by mixing poly(vinyl alcohol) PVA (Kuraray 117H Mw 74800 saponification 99.6%), poly(acrylic acid) PAA (SP2 Mw 170000), and poly(allylamine) hydrochloride PAlAm.HCl (Nittobo Mw 60000) a homogeneous aqueous solution of PVA PAA PAlAm was obtained at concentrations of 

To examine the effect of the freezing rate on the internal structure and the mechanical properties of hydrogels we made three types of gel film A, B and C by changing the freezing rate from 3.78, 0.0766 to 0.0329 Ks1, respectively, at the freezing point. 

---