Real-time observation of conformational switching in single conjugated polymer chains.

Conjugated polymers (CPs) are an important class of organic semiconductors that combine novel optoelectronic properties with simple processing from organic solvents. It is important to study CP conformation in solution to understand the physics of these materials and because it affects the properties of solution-processed films. Single-molecule techniques are unique in their ability to extract information on a chain-to-chain basis; however, in the context of CPs, technical challenges have limited their general application to host matrices or semiliquid environments that constrain the conformational dynamics of the polymer.

Effect of chiral 2-ethylhexyl side chains on chiroptical properties of the narrow bandgap conjugated polymers PCPDTBT and PCDTPT.

Two narrow bandgap conjugated polymers containing chiral 2-ethylhexyl side chains were synthesized: poly[(4,4-bis(2-ethylhexyl)cyclopenta-[2,1-:3,4-']dithiophene)-2,6-diyl--(2,1,3-benzothiadiazole)-4,7-diyl] (PCPDTBT*) and poly[(4,4-bis(2-ethylhexyl)cyclopenta[2,1-:3,4-0]dithiophene)-2,6-diyl--[1,2,5]-thiadiazolo[3,4-]pyridine] (PCDTPT*). The presence of a chiral substituent provides a handle to study the geometry of interchain aggregates and/or the secondary structure of these conjugated polymers in solution and in thin films circular dichroism (CD) spectroscopy, provided that the asymmetry in the side-chain is translated to the optically active conjugated backbone. CD signals are observed for PCPDTBT* and PCDTPT* in poor solvent systems, which indicate the presence of chiral ordering in the aggregates.

Tethered tertiary amines as solid-state n-type dopants for solution-processable organic semiconductors.

A scarcity of stable n-type doping strategies compatible with facile processing has been a major impediment to the advancement of organic electronic devices. Localizing dopants near the cores of conductive molecules can lead to improved efficacy of doping. We and others recently showed the effectiveness of tethering dopants covalently to an electron-deficient aromatic molecule using trimethylammonium functionalization with hydroxide counterions linked to a perylene diimide core by alkyl spacers.

Electrical properties of doped conjugated polyelectrolytes with modulated density of the ionic functionalities.

We report the synthesis of a series of water-soluble anionic narrow band-gap conjugated polyelectrolytes with a varied density of the ionic functional groups. The charge density is modulated by incorporating the structural units with tetraethylene glycol (TEG) monomethyl ether side chains. These polymers are readily p-doped during dialysis in water.

Side-chain effects on the conductivity, morphology, and thermoelectric properties of self-doped narrow-band-gap conjugated polyelectrolytes.

This contribution reports a series of anionic narrow-band-gap self-doped conjugated polyelectrolytes (CPEs) with π-conjugated cyclopenta-[2,1-b;3,4-b']-dithiophene-alt-4,7-(2,1,3-benzothiadiazole) backbones, but with different counterions (Na(+), K(+), vs tetrabutylammonium) and lengths of alkyl chains (C4 vs C3). These materials were doped to provide air-stable, water-soluble conductive materials. Solid-state electrical conductivity, thermopower, and thermal conductivity were measured and compared.