11467
The polyethylenimine ( PEI ) derivatives ( PTn ) are prepared by treating PEI25k with Tris ( hydroxymethyl ) acrylamidomethane via the Michael addition .
 Chemical: polyethylenimine; Chemical: PEI; Chemical: Tris ( hydroxymethyl ) acrylamidomethane
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: polyethylenimine; Chemical: PEI; Chemical: Tris ( hydroxymethyl ) acrylamidomethane