Polymer and Materials Science
Wiley InterScience Backfile Collection 1832-2000
Chemistry and Pharmacology
A novel planar ↔ nonplanar visual thermochromic conformational transition of polydiacetylene molecules in poor solvents is reported. The conformational transition is associated with both a color change (blue or red ↔ yellow) and a change in the state; the yellow solution (liquid) transforms to a blue or red gel (solid). The color transition occurs within a narrow range of temperature and has a large associated hysteresis. The enthalpy of the conformational transition is 29 kJ/mole of repeat unit. Fourier-transform infrared studies show that molecules acquire a planar conformation in red or blue gels by formation of intramolecular H bonds between the adjacent substituent groups. Virtually all H bonds break (a nonplanar conformation) when the gels turn into yellow solutions.
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