Structurally Diverse Poly(thienylene vinylene)s (PTVs) with Systematically Tunable Properties through Acyclic Diene Metathesis (ADMET) and Postpolymerization Modification

Abstract

Poly­(thienylene vinylene)­s (PTVs) are a unique class of low bandgap conjugated polymers that have received relatively little attention in organic electronic applications due to the limitations in conventional synthetic methodologies that are not capable to produce PTV structures beyond the rudimentary forms. We report here facile synthetic methods, combining acyclic diene metathesis (ADMET) and postpolymerization modification reactions, toward a series of structurally diverse PTVs. Specifically, halogen substituents including F, Cl, Br, and I, and conjugated thienyl groups bearing different substituents, have been installed onto every thiophene unit along the PTV backbones. While halogen substitution lowers both the HOMO and LUMO energy levels of the polymers, the overall optical properties are similar to the conventional unsubstituted PTVs. On the other hand, with increasing sizes of halogen atoms, the polymer crystallinity decreases caused by steric hindrance induced main-chain nonplanarity as suggested by density functional theory (DFT) calculations and confirmed by X-ray diffraction (XRD) and absorption measurements. With the cross-conjugated thienyl side-chains, the PTV polymers are all amorphous due to the large dihedral angles between the main-chain and side-chain thienyl rings. However, with strongly electron-withdrawing groups attached on the side-chain thiophene rings, new electronic transitions located at lower energies are observed, which have never been observed in PTVs and are assigned to main-chain to side-chain intramolecular charge transfer (ICTs) transitions. Such ICT transitions can potentially alter the PTV excited states ordering and dynamics, as evidenced by the appearance of fluorescence in one of the cross-conjugated PTVs bearing strong electron-withdrawing cyanoester vinylene groups. Applications of these new PTVs in bulk heterojunction (BHJ) organic solar cells (OSCs) have been attempted, and preliminary results showed much improved performances over devices using conventional PTVs, especially for those applying the cross-conjugated PTVs. Our methodologies are highly versatile in preparing PTVs with systematically varied structures that for the first time provide means to study and gain better understandings on the structure–property relationships of this unique class of materials and to potentially generate novel polymers tailor-designed for specific electronic applications.

Preparation of Vinyl Arenes by Nickel‐Catalyzed Reductive Coupling of Aryl Halides with Vinyl Bromides

“…[10][11][12] It was however surprising to note that investigations on the reductive coupling between aryl and vinyl electrophiles are exceptionally rare, [13][14][15][16] although vinyl arenes are as ocalled privileged scaffold found in bioactive natural products, pharmaceuticals,a nd polymers. [17] An example known in the literature emphasizes as trategy involving cobalt catalysis. [13,14] However,t his method is constrained to very limited vinyl substrates.D ropwise addition of vinyl halides to 2equivalents of an aryl bromide was key to avoiding the dimerization of individual halides (Scheme 1).…”

ADMET Polymerization: Greener Method for Synthesis of End-Functionalized Poly(Arylene Vinylene)s

“…This methodology therefore afforded synthesis of defect free, high molecular weight, all trans poly(9,9-di-n-octyl-fluorene-2,7-vinylene) (PFV) [30], poly(2,5-dialkyl-pheny-lene-1,4-vinylene)s (PPVs) [31], and poly(N-alkylcarbazole-2,7-vinylene)s (PCVs) [32], poly(thienylene vinylene)s [34]- [40] by using Schrock type molybdenum-alkylidene, and ruthenium-carbene catalysts (Scheme 6). The resultant polymers [30] [31] [32] possess high stereo-regularity (all trans olefinic double bond) and analytically pure (defect-free), and showed unique photophysical properties compared with polymers prepared by other methods.…”

“…Synthesis of poly(thienylene vinylene) by ADMET polymerization using Ru-carbene catalysts [34]- [40].…”

Modified structure of two-dimensional polythiophene derivatives by incorporating electron-deficient units into terthiophene-vinylene conjugated side chains and the polymer backbone: synthesis, optoelectronic and self-assembly properties, and photovoltaic application

“…5,[17][18][19][20] Poly(thienylenevinylene)s (PTVs), which is one of polythiophene derivatives (PTs) containing alternating thiophene and vinylene units along the main-chains, have been intensively studied for their photoelectrical property and photovoltaic applications, due to their good charge transport property. 2,[21][22][23][24][25] In addition, previous literatures also have shown that polythiophene derivatives (PTs) with thienylene-vinylene conjugated side chains possess broader absorption spectra and relatively low-lying HOMO energy levels compared with their linear analogues, since the thienylene-vinylene conjugated side chains could extend the p-electron delocalization of polymer backbone. 2,[26][27][28][29][30] For example, chemically graing conjugated side chains onto polymer backbone through vinylene-linkage, such as thienylene-vinylene 31 and bi(thienylenevinylene), 11 is effective to extend the absorption range and down-shi the HOMO energy level of polythiophene.…”