Donor-acceptor (DA) type monomers namely 2,5-di(thiophen-2-yl)thiazolo[5,4-d]thiazole (TTzTh) and 2,5-bis(3-methylthiophen-2-yl)thiazolo[5,4-d]thiazole (TTzMTh) were synthesized and their electrochemical and optoelectronic properties were investigated in detail. The spectro-electrochemical analysis showed that the alkyl chain substitution results in a shift in the onset of the pi-pi* transition towards longer wavelengths. Depending on the donor substituents, the polymers exhibited optical band gaps 1.65 and 1.85 eV for PTTzTh and PTTzMTh, respectively. Electrochromic studies revealed that both polymers are p-dopable and multichromic. Moreover, polymer of TTzTh (PTTzTh) has been used for the development of a glucose biosensor. Glucose oxidase (GOx) was anchored on a graphite electrode which was previously modified with a film of the conjugated polymer, PTTzTh by electropolymerization. Such a sensor showed a wide linear range (0.05 - 2.0 mM), good sensitivity (36.32 mu A/(mM.cm(2)) and low limit of detection (LOD) (0.075 mM) under formerly optimized conditions. Moreover, the accuracy of the biosensor was successfully tested using two different beverages to detect glucose. Electrochemical characterizations of the polymers and their biosensor application were investigated for the first time in this work.