We describe the synthesis and structure property relationships of two branched electroactive monomers containing carbazole core, 2,5-di(2-thienyl)-1H-pyrrole, differentiated by the length of side alkyl chains (DSNSC-1 and DSNSC-2). Structural identification of initial compounds and products were carried out by using FT-IR and H-1 and C-13 NMR spectroscopy. The electroactive materials DSNSC-1 and DSNSC-2 were directly coated on to ITO glass surface by using electrochemical polymerization process. The results clearly indicate that the length of side alkyl chain has a major impact on optical and electrochemical properties of these polymers. Poly-DSNC-2 with longer side alkyl chain exhibits a high contrast ratio (Delta T% = 68% at 850 nm), a response time of about 0.8 s, and high coloration efficiency (352 cm(2) C-1) and retained its performance by 97.1% even after 5000 cycles.