Temperature‐responsive characteristics of N ‐isopropylacrylamide‐grafted polymer films prepared by photografting

Photografting of N ‐isopropylacrylamide (NIPAAm) on ethylene–vinyl alcohol copolymer films (thickness = 15,20, and 25 μm) and low‐and high‐density polyethylene films (thickness = 30 μm) was carried out at 60°C in a water medium. Xanthone was used as a photoinitiator by coating it on the film samples. The resultant NIPAAm‐grafted films exhibited a temperature‐responsive character, which was evaluated by measuring a dimensional change of the grafted films. The grafted films swelled and shrank in water at temperatures lower and higher than around 30°C, respectively. The character was found to be reversible between 0 and 50°C. It was observed that the extent of the character is largely influenced by film thickness, location of NIPAAm‐grafted chains, and crystallinity of film substrate. © 1994 John Wiley & Sons, Inc.