6908
Simulations of multiple copies of the SWNT in water show that all pure SWNTs aggregate , lipid - wrapped SWNTs partially aggregate , but those wrapped with lipids grafted to PEG ( M ( w ) = 550 ) completely disperse , indicating the effect of short PEG chains on interparticle aggregation , in agreement with experiment .
 Chemical: PEG; Chemical: PEG
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: PEG; Chemical: PEG