Experiment 4 . Polyvinyl alcohol (12 g.) was slurried with 88 ml. 

 of cold water, then heated with stirring to effect solution. Additional 

 water was added to lower the viscosity. Oxalic acid (3 g.) and glycerol 

 (10 g.) were added, stirring was continued, the temperature of the solu- 

 tion was raised to 95 , and heating was continued for one hour. Then 

 the solution was set aside to cool. A sample was transferred to a Petri 

 dish and heated to 100 under an infrared lamp to drive off water; then 

 it was heated at 135 for three hours and cooled to room temperature. 

 A sample of the tough film which had formed lost its strength in boiling 

 water and in cold water. 



Experiment 5 . In a 500 ml. round-bottomed flask were placed 4,4' 

 sulfonyldiphenol (dihydroxydiphenylsulfone) (25 g.), formalin (36 g., 

 36.6%), sodium hydroxide (8 g.) , and water (72 g.). A solution formed 

 and was refluxed for 6% hours and allowed to cool to room temperature. 

 Sodium bisulfite (5 g.) was added and dissolved. The solution was poured 

 into a 1000 ml. beaker, ice was added, and the solution was acidified 

 with 20% sulfuric acid. A white precipitate formed and was collected 

 on a Buechner filter, was washed with water, and was sucked as dry as 

 possible. The damp solid was transferred to an evaporating dish, cut 

 into small pieces, and set aside to dry. When dry it was powdered. 

 Then 0.05 g. was added to a methanol-water solution of polyvinyl alcohol 

 (0.45 g.) and dissolved, A portion of the solution was poured into a 

 Petri dish, dried at room temperature, and heated at 150 for one hour. 

 The film which was produced was resistant to cold water. When the film 

 was formed by casting on a Teflon^ sheet, drying at room temperature 

 and heating at 150 for one hour, it broke without yielding and lost 

 strength when immersed in water. 



Acrylamide 



Experiment 1 . Polyacrylamide (6 g.) was mixed with water (194 ml.) 

 in a blender, after which 0.25 percent dialdehyde starch solution (5 g.) 

 was added and the pH adjusted to two with concentrated hydrochloric acid. 

 A sample was poured into a Petri dish and heated under an infrared lamp. 

 The film which formed was not water resistant. 



Experiment 2 . A solution containing 35 g. of a mixture of acrylam- 

 ide and N,N-methylenebisacrylamide in 80 ml. of water was mixed with 

 15 g. of an aqueous solution containing five percent polyvinylpyrrolidone 

 and 2.5 percent sulfur dioxide (as sulfurous acid). An exothermic 

 reaction occurred, and within a few minutes, a gel had formed. When 

 placed in cold water the gel absorbed water and softened. 



The experiment was repeated except that gelatin was used instead 

 of polyvinylpyrrolidone. Again, an exothermic reaction yielded a gel. 

 When placed in cold water, the gel absorbed water and softened. Similar 

 results were obtained when neither polyvinylpyrrolidone nor gelatin were 

 used. 



