page_title: Tellurophenes
section_title: Polymers
hierarchical_section_title: Tellurophenes / Reactivity / Polymers
caption_attribution_description: English: Synthesis of P3TeV using Stille coupling
context_page_description: Tellurophenes are the tellurium analogue of thiophenes and selenophenes.
context_section_description: In 2016, Seferos et al. reported the synthesis of well-defined, high-molecular-weight poly-3-alkyltellurophenes (P3ATe) through catalyst transfer polymerization (CTP). CTP is an important route to synthesize polymers with a narrow molecular weight distribution and a well defined end-group, but it was found in 2013 that applying CTP-conditions for the synthesis of P3ATe led to polymers with low molecular weights, and broad polydispersities. To obtain P3ATe with a narrow polydispersity, the authors investigated the optimal conditions using kinetic studies and DFT calculations. It was found experimentally that the branched side chain played an important role on the polymerization rate and polymer quality. To mitigate this effect, monomers with various other side chains were synthesized. From this, it was found that moving the ethyl branches away from the heterocycle to the more remote 3- and 4- positions led to an improved polymerization rate and control, such that P3ATe with narrow polydispersities and high molecular weights were obtained. This improvement was attributed to the lack of steric hindrance. Furthermore, it was found that upon moving the branching point away from the heterocycle led to a red-shift in the optical absorption, which was attributed to a decrease in the degree of twisting, resulting in an increase in the conjugation between the tellurophene backbone.
  Heeney et al. reported the synthesis of the first tellurophene-vinylene copolymer through Stille coupling of 2,5-dibromo-3-dodecyltellurophene and (E)-1,2-bis(tributylstannyl)ethylene, resulting in P3TeV in 57% yield with an approximate Mₙ of 10 kDa and a polydispersity of 2.4. By synthesizing thiophene and selenophene analogues, it was found that there was a reduction in the optical band gap as a result of the stabilization of the LUMO, resulting in a small band gap of 1.4 eV for P3TeV. By constructing organic field effect transistors (OFETs), it was found that the selenophene polymer had the highest charge mobility, and that the tellurium analogue did not lead to an increase in mobility despite the larger size of tellurium, and possibility of closer interchain Te-Te interactions, which was attributed to the low solubility of P3TeV which resulted in poor film formation. Therefore, the authors remarked that future work entailed modifying the side-chains to increase solubility.
caption: Synthesis of P3TeV using Stille coupling[29]
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