Studies on homologous random and alternating segmented conjugated polymers with and without silicon synthesized by ADMET

Abstract

Using acyclic diene metathesis (ADMET), we synthesized homologous luminescent conjugated polymers with two aromatic segments based on thiophene and substituted phenylene, either alternating or randomly distributed, and either directly connected or separated by Si-linkers. In the polymers with M_n ∼ 5000–14 600 g mol⁻¹, random or alternating placement of two segments yielded similar electro-optical properties (absorption λ_max at ∼363 nm, emission, λ_max ∼ 411 nm, HOMO–LUMO gap 3.00–3.07 eV), although alternating segments showed a slightly more defined absorption with slightly higher absorptivity and emission efficiency (57% vs. 51%). The alternating segments directly conjugated (without Si-linkers) showed a longer wavelength absorption and emission (λ_max at ∼490 nm and ∼556 nm respectively), and slightly lower emission efficiencies (40%), as well as a smaller HOMO–LUMO gap of 2.21 eV. DFT calculations support the above results and analyses. Understanding such specific interactions between the aromatic units might provide guidance for future designs of segmented conjugated polymers.