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We developed a new synthetic approach to high molecular weight poly ( p - phenylenebutadiynylene ) s ( PPBs ) by increasing backbone flexibility .
 Chemical: poly ( p - phenylenebutadiynylene ) s; Chemical: PPBs
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 ( p - phenylenebutadiynylene ) s; Chemical: PPBs