π-Conjugated polymers consisting of heavier group 13 elements

Boron, aluminum, gallium, indium, and thallium are group 13 elements that can induce various electronic properties and unique functions when incorporated into main-chain conjugation through polymers. As vacant p-orbitals in these elements interact with Lewis bases, stimuli responsiveness can be induced. Additionally, the chemical and thermal stability can be enhanced by connecting with extra Lewis bases as supporting ligands. Moreover, superior optoelectronic properties, such as light absorption, emission, and carrier mobility, are often observed from group 13 element-containing π-conjugated systems. The introduction of boron into conjugated systems has been widely applied not only for improving material properties but also for providing new functionalities for conventional polymers. In contrast, there are limited examples of polymers possessing the heavier group 13 elements in their repeating units. According to recent studies, it has been shown that the chemical, physical, and material properties of π-conjugated compounds can be unexpectedly modulated by these heavier group 13 elements. In this review, we mainly explain the synthesis and fundamental photophysical properties of conjugated polymers consisting of the heavier group 13 elements in their main-chains.