A New Solution to an Old Problem: Synthesis of Unsubstituted Poly(para-phenylene)

Abstract

Unsubstituted and structurally well-defined poly(para-phenylene) (PPP) has been long-desired as an organic semiconductor prototype of conjugated polymers. To date, several attempts to synthesize unsubstituted, pristine, high-molecular-weight PPP have failed. Here we solved this synthetic problem by a versatile precursor route. Suzuki polymerization of kinked disubstituted 1,4-dimethoxycyclohexadienylene monomers yielded a well-soluble, nonaromatic precursor polymer. Its solubility allowed processing by spin-coating into nanometer-thick films. Subsequent additive-free thermal treatment induced aromatization and led to exclusively para-connected, highly fluorescent PPP with a length of about 75 phenylene units.

Chiroptical Properties of Twisted Acenes: Experimental and Computational Study

“…[21] Nevertheless,t his effect is an indicationt hat p-orbital overlap is not disturbed significantly in acenes, even for a3 0 8 twist perb enzene ring. [14] This contrasts sharplyw ith the response of oligophenylenes to twisting, [22] and so highlights the advantage conferredb yf used polyaromatic systems during backbonet wist. The ECD spectra for parenta cenes are composed of several main bands in the region > 250 nm, with two bands in the lowest energy region displaying opposite signs ( Figure 3).…”

“…Nevertheless, this effect is an indication that π‐orbital overlap is not disturbed significantly in acenes, even for a 30° twist per benzene ring . This contrasts sharply with the response of oligophenylenes to twisting, and so highlights the advantage conferred by fused polyaromatic systems during backbone twist.…”

Direct synthesis of polyaromatic chains of tribenzopentaphene copolymers through cyclodehydrogenation of their poly‐tetraphenylbenzene precursors

“…The emission spectrum of 5b portrays a ∼23 nm blue shift with respect to that of 4b . This could be explained by the long range conjugation between the different aromatic groups in 4b , namely, the terphenyl derivatives and bithiophene moieties whose smaller size and free rotation allows for a long range planarization, and which can be compared with the structure and optical properties of poly‐( p ‐phenylenes) . This is further supported by the DFT calculations revealing a pseudo‐planar phenylene‐bithiophene chains (Supporting Information Table S1).…”

“…It is noteworthy that opto‐ and electroactive polymers mainly consist of fused heterocyclic building blocks and their derivatives, whereas less attention has been drawn to poly‐PAHs whose lack of effective synthesis and scarce solubility represent the utmost challenges. Recently, more interest has been drawn in making polyphenylenes and triphenylene‐based polymers …”

Spiers Memorial Lecture : Carbon nanostructures by macromolecular design – from branched polyphenylenes to nanographenes and graphene nanoribbons

“…An advantage of precursor protocols for polymer synthesis is often that the precursors are more soluble and can be processed from solution, followed by transformation into the target polymer. 145 In the case of GNR 62, surprisingly, solution liquid-phase processing is still possible. As described for NGs in section 2.1, this is due to the attached alkyl chains.…”