18666
These copolymers were freely soluble in phosphate buffer but formed disulfide - cross - linked nanogels with defined sizes ranging from 72 . 5 to 124 . 1 nm in the presence of cystamine via ring - opening reaction with cyclic carbonate groups .
 Chemical: phosphate; Chemical: disulfide; Chemical: cystamine; Chemical: cyclic carbonate
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: phosphate; Chemical: disulfide; Chemical: cystamine; Chemical: cyclic carbonate