Based on first principles density functional theory, structural, electronic, and optical properties of poly (3-thiophene boronic acid) organic polymer have been calculated. It consist of positively charged pending boronic acid and negatively charged polymerized thiophene backbone which have anionic polymerization as in the type of vinyl polymerization. Electro-optical properties of the polymer indicates that it is not only an extrinsic (p-type) semiconductor with the electronic band gap, E-g = 1.35 eV, but also a perfect reflector polymer in the red band from 1.66 eV (similar to 747 nm) to 1.91 eV (similar to 650 nm). However, its refractive index diminishes at around 1.91 eV (similar to 650 nm) interestingly. These results suggest that, it will be a very promising multi-functional polymer for both academia and industries of electronic and optical device technologies. (C) 2016 Society of Plastics Engineers