6453
Novel block copolymers comprising poly ( ethylene glycol ) ( PEG ) and an oligo ( tyrosine ) block were synthesized in different compositions by N - carboxyanhydride ( NCA ) polymerization .
 Chemical: poly ( ethylene glycol ); Chemical: PEG; Chemical: oligo ( tyrosine ); Chemical: N - carboxyanhydride; Chemical: NCA
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: poly ( ethylene glycol ); Chemical: PEG; Chemical: oligo ( tyrosine ); Chemical: N - carboxyanhydride; Chemical: NCA