Stiffness and Conformational Transition of Poly{3-[(5)-2-methylbutoxy]phenyl isocyanate} in Dilute Solution

摘要

Poly{3-[(S)-2-methylbutoxy]phenyl isocyanate} was shown to be locally helical,but a rather flexible wormlike chain of persistence length 3 nm.Its optical activity changed remarkably on temperature-solvent and molecular weight,vanishing at a specific temperature T_c irrespective of molecular weight,exhibiting a cooperative transition of helical conformations.Such optical activity data were well explained by a theory of Lifson et al.on the helix reversal model,taking the conformations of the terminal residues explicitly.This polymer is locally helical and rodlike because of its conjugating main-chain amide bonds,which are conjugating also with side-chain phenyl rings.However,the latter conjugation weakens the main-chain stiffness,with almost no contribution to the global stiffness from helix reversal points.