8652
The film - substrate interaction plays an essential role in nanostructuring of Nafion (R) thin films , which may also be the case for Nafion (R) on the catalysts of polymer electrolyte fuel cells .
 Nafion, Nafion
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 Nafion, Nafion