Conducting polyfurans by electropolymerization of oligofurans.

Polyfurans have never been established as useful conjugated polymers, as previously they were considered to be inherently unstable and poorly conductive. Here, we show the preparation of stable and conducting polyfuran films by electropolymerization of a series of oligofurans of different chain lengths substituted with alkyl groups. The polyfuran films show good conductivity in the order of 1 S cm-1, good environmental and electrochemical stabilities, very smooth morphologies (roughness 1-5 nm), long effective conjugation lengths, well-defined spectroelectrochemistry and electro-optical switching (in the Vis-NIR region), and have optical band-gaps in the range of 2.2-2.3 eV. A low oxidation potential needed for polymerization of oligofurans (compared to furan) is a key factor in achievement of improved properties of polyfurans reported in this work. DFT calculations and experiments show that polyfurans are much more rigid than polythiophenes, and alkyl substitution does not disturb backbone planarity and conjugation. The obtained properties of polyfuran films are similar or superior to the properties of electrochemically prepared poly(oligothiophene)s under similar conditions.

Polymeric memory elements and logic circuits that store multiple bit states.

The ever-increasing flow of information requires new approaches for high-density data storage (HDDS). Here, we present a novel solution that incorporates the easily accessible polymer poly(3,4-ethylenedioxythiophene) (PEDOT) with multistate memory. The electrical addressable polymer is able to store up to five different memory states, which are stable up to 20 min. The observed memory states are generated by the optical output signature of the PEDOT deposited on indium tin oxide (ITO) coated glass, upon applying specific electrical inputs. Moreover, the demonstrated platforms can be represented by a general logic circuit, which allows the construction of multistate memory, such as flip-flops and flip-flap-flop logic circuits.

Synthesis, structure, and electropolymerization of 3,4-dimethoxytellurophene: comparison with selenium analogue.

3,4-Dimethoxytellurophene (5) was synthesized via a new ring construction reaction. The crystal structure of 5 is characterized by unusually short Te...Te distances. The electropolymerization of 5 probably produces some amount of poly-5. Since the product was unstable under experimental conditions, a definitive assignment could not be made. However, the UV-vis spectrum recoded during electropolymerization of 5 shows an absorption peak at 679 nm with an onset at 820 nm (1.51 eV), closely matching the calculated band gap of poly-5.

Rubrenes: planar and twisted.

Surprisingly, despite its very high mobility in a single crystal, rubrene shows very low mobility in vacuum-sublimed or solution-processed organic thin-film transistors. We synthesized several rubrene analogues with electron-withdrawing and electron-donating substituents and found that most of the substituted rubrenes are not planar in the solid state. Moreover, we conclude (based on experimental and calculated data) that even parent rubrene is not planar in solution and in thin films. This discovery explains why high mobility is reported in rubrene single crystals, but rubrene shows very low field-effect mobility in thin films. The substituted rubrenes obtained in this work have significantly better solubility than parent rubrene and some even form films and not crystals after evaporation of the solvent. Thus, substituted rubrenes are promising materials for organic light-emitting diode (OLED) applications.

Poly(3,4-ethylenedioxyselenophene).

The first highly conductive polyselenophene, namely, poly(3,4-ethylenedioxyselenophene) (PEDOS), was synthesized by taking advantage of a novel method for efficiently contracting the selenophene ring. PEDOS shows a relatively low band gap (1.4 eV), very high stability in the oxidized state, and a well-defined spectroelectrochemistry.