7542
In contrast to rubber - like biopolymers , the retractive elastic force in these biomacromolecular materials is not dominated by a return to a maximum entropic state , but is mostly the result of variations in internal energy associated with the conformational changes .
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Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
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