Controlling Thermochromism in a Photonic Block Copolymer Gel

Joseph J. Walish, Yin Fan, Andrea Centrone, Edwin L. Thomas*  

This report presents a way to modulated the reflective properties of a gel.  In this case, a PS-P2VP block-copolymer in a lamellar microstructure is a gel that can swell in only one direction b/c of the constraint imposed by the glassy PS domain.  The swelling is achieved by reversible temperature-induced pKa change of the pyridinium moiety (decreases with temperature).  Increase in P2VP domain thickness causes specific light frequencies to interfere constructively when reflected from the sample, and these frequencies are dependent on the thickness of the repeating domains.

 

http://onlinelibrary.wiley.com/doi/10.1002/marc.201200355/full