oligo-/polyselenophenes, compared to other types of conducting polymers, exhibit several special properties and advantages including lower band gaps, more planar backbones, stronger intermolecular interactions (including Se–Se interactions), greater degrees of doping, etc. However, the design and synthesis of novel polyselenophenes-based polymers with improved properties sufficing for applications are significant and still present a considerable challenge. Most recently, in China, Lu et al synthesized a series of novel selenophene–EDOT oligomers and their electropolymerization led to the facile deposition of highly stable conducting copolymers with band gaps ranging from 1.54 to 1.75 eV. Further investigation demonstrated that the obtained copolymers display amazing optoelectronic properties, such as outstanding electroactivity and stability, enhanced main chain planarity, electrochromic nature with colour changing from purplish, reddish and saturated blue in the reduced form to transparent sky blue/green upon oxidation, etc. Electrochromic kinetic studies showed that these copolymers revealed decent contrast ratios, favorable coloration efficiencies, low switching voltages, fast response time, excellent stability and colour persistence, holding promise for display applications. Clearly, these copolymers featured the combined advantages of polyselenophene and PEDOT, such as lower band gap and better planarity of polyselenophene and high conductivity, transparency and excellent stability of PEDOT. Moreover, their method by designing the copolymers of selenophenes with other units presents an effective way to overcome the disadvantages of polyselenophenes while retaining their beneficial qualities. A portfolio of these materials holds promise for rational design of some unique optoelectronic materials, and may find application in electrochemical sensors and organic electronic devices.
Polym. Chem., 2014,5, 4896-4908.
Baoyang Lu,ab Shijie Zhen,b Shimin Zhang,b Jingkun Xu*ab , Guoqun Zhao*a
a-Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials (Ministry of Education), Shandong University, Ji’nan, PR China and
b-School of Pharmacy, Jiangxi Science & Technology Normal University, Nanchang 330013, China.
A family of four novel selenophene–EDOT oligomers were synthesized using Stille coupling and electropolymerized to form highly stable conducting hybrid polymers with excellent electrochromic properties. Structure–property relationships of the oligomers and hybrid polymers, including electrochemical, electronic and optical properties, quantum chemistry calculations and morphology, were systematically explored. The oligomer precursors with planar structures exhibit blue to orange emission characteristics with quantum yields ranging from 1.5 to 9.0%; they may be used as building blocks for the rational design of fluorescent conjugated systems with enhanced main chain planarity. Cyclic voltammetry shows low oxidation potentials ranging from 0.53 to 0.89 V vs. Ag/AgCl, leading to the facile electrodeposition of uniform hybrid polymer films with outstanding electroactivity and stability at low oxidation potentials. The obtained hybrid polymers featured the combined advantages of polyselenophene and PEDOT, such as the lower band gap and better planarity of polyselenophene and the high conductivity, transparency and excellent stability of PEDOT. The hybrid polymers show planar π-conjugated backbones with band gaps ranging from 1.54 to 1.75 eV. They are electrochromic in nature with colour changing from purplish, reddish and saturated blue in the reduced form to transparent sky blue/green upon oxidation. Further kinetic studies demonstrated that the hybrid polymers have decent contrast ratios (22–36%), favourable coloration efficiencies (200 cm2 C−1), low switching voltages, fast response time (0.5 s), excellent stability and colour persistence. These materials provide more plentiful electrochromic colours and hold promise for display applications.