Poly 3-oligo -4-methylthiophene

Some other 3-thienyl ether derivatives have been prepared. Poly[3-oligo(oxyethylene)-4-methyltiophene] showed an absorption peak at 550 nm (95JCS(CC)2293). On the other hand, poly[3-(N-succinimido(tetra-ethoxy)oxy)-4-methylthiophene] was prepared and it is able to react with amines to give the corresponding carbamate with a 15-crown-5 attached substructure. This polymer showed absorption at 429 nm and fluorescence at 543 nm (04T11169). 

FIGURE 9.2 Variation of the absorbance of the 426 nm band of poly[3-oligo(oxyethylene)-4-methylthiophene] (1.0-10 " M) in methanol as a function of the concentration of various salts at 22 °C. Reproduced with permission from [10]. Copyright 1996 American Chemical Society. 

Thermochromism. Neutral poly(3-alkylthiophene)s and poly(3-alkoxy-4-metiiylthiophene)s exhibit strong chromic effect upon heating both in the solid state and in solution[25-2P]. Two types of thermochromic behavior can be observed and are correlated to the substitution pattern of the polymers. As an example of the first type (the two-phase behavior), the temperature dependence of the absorbance of a thin film of poly[3-oligo(oxyethylene)-4-methylthiophene] [57] is shown in Figure 4. 

More dramatic effects were observed with regioregular polyether-substituted polythiophenes. As reported by Levesque and Leclerc, chemically synthesized head-to-tail poly[3-oligo(oxyethy-lene)-4-methylthiophene] poly(5) led to ionochromic effects, with a clear isosbestic point on the UV-visible absorption spectrum, indicating the coexistence of long sequences of nonplanar and planar thiophene units [244, 245]. With the addition of a cation such as the main chain became twisted. However, in contrast to poly(4), this phenomenon was observed only with the polymer in solution. 

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