Chemistry Reference
In-Depth Information
Figure 12.13 Polythiophene sensing schematic. Reprinted from McCullough (1998).
Copyright 1998 Wiley-VCH Verlag GmbH and Co. KGaA.
hydroxides resulted in the formation of colored solutions. Larger cations resulted in
the formation of red, orange, or yellow solutions, whereas small cations afforded sol-
utions that were purple, the color of the polymer in the solid state. The smaller cations
are believed to favor formation of organized stacked assemblies of polymers, whereas
larger cations form more disordered aggregates (Fig. 12.13).
Polythiophenes functionalized with monosaccharides have been evaluated for their
ability to detect the influenza virus and E. coli (Baek et al. 2000). Copolymers of thio-
phene acetic acid 10 and carbohydrate-modified thiophenes 11 have been prepared via
iron(III) chloride mediated polymerization. Addition of influenza virus to a sialic acid
containing copolymer resulted in a blue shift of the polymer absorption maximum,
resulting in an orange to red chromatic transition. Mannose-containing polythiophenes
underwent color changes upon the addition of the lectin ConA or E. coli cells that
contain cell surface mannose-binding receptors. A similar biotinylated polythiophene
afforded a streptavidin responsive material (Faid and Leclerc 1996).
A modular and flexible approach to polythiophene sensors based on the poly-
merization of a thiophene-activated ester has been reported (Bernier et al. 2002).
Subsequent reaction of the polymerized NHS ester with a variety of diamines
permits the synthesis of sensors for different analytes from a common platform.
For example, reaction of the NHS polymer with an aminomethyl-modified
15-crown-5 derivative yielded a polymer that underwent color changes in the
presence of alkali cations (Fig. 12.14).
The carboxylic acid functionalized polythiophene 9 has been used to detect and
identify a variety of different diamines (Nelson et al. 2006). Addition of various
diamines to a solution of the carboxy polythiophene induces crosslinking of the
