26141
All copolymers are water - soluble at low temperature , but upon quickly heating to 37 degrees C , laser light scattering ( LLS ) and transmission electron microscopy ( TEM ) characterizations indicate that these copolymers self - assemble into aggregates with different morphologies depending on the chain length of PtNEA and the polymer concentration ; the morphologies gradually evolved from spherical solid nanoparticles to a polymersome as the degree of polymerization ( " n " ) of PtNEA block increased from 22 to 172 , with the formation of clusters with rod - like structure at the intermediate PtNEA length .
 PtNEA, PtNEA, PtNEA
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 PtNEA, PtNEA, PtNEA