Sterically-Hindered Molecular p-Dopants Promote Integer Charge Transfer in Organic Semiconductors.

Molecular p-dopants designed to undergo electron transfer with organic semiconductors are typically planar molecules with high electron affinity. However, their planarity can promote the formation of ground-state charge transfer complexes with the semiconductor host and results in fractional instead of integer charge transfer, which is highly detrimental to doping efficiency. Here, we show this process can be readily overcome by targeted dopant design exploiting steric hindrance. To this end, we synthesize and characterize the remarkably stable p-dopant 2,2',2''-(cyclopropane-1,2,3-triylidene)tris(2-(perfluorophenyl)acetonitrile) comprising pendant functional groups that sterically shield its central core while retaining high electron affinity. Finally, we demonstrate it outperforms a planar dopant of identical electron affinity and increases the thin film conductivity by up to an order of magnitude. We believe exploiting steric hindrance represents a promising design strategy towards molecular dopants of enhanced doping efficiency.

Macromolecularly Engineered Thermoreversible Heterogeneous Self-Healable Networks Encapsulating Reactive Multidentate Block Copolymer-Stabilized Carbon Nanotubes.

The development of heterogeneous covalent adaptable networks (CANs) embedded with carbon nanotubes (CNTs) that undergo reversible dissociation/recombination through thermoreversibility has been significantly explored. However, the carbon nanotube (CNT)-incorporation methods based on physical mixing and chemical modification could result in either phase separation due to structural incompatibility or degrading conjugation due to a disruption of π-network, thus lowering their intrinsic charge transport properties. To address this issue, the versatility of a macromolecular engineering approach through thermoreversibility by physical modification of CNT surfaces with reactive multidentate block copolymers (rMDBCs) is demonstrated. The formed CNTs stabilized with rMDBCs (termed rMDBC/CNT colloids) bearing reactive furfuryl groups is functioned as a multicrosslinker that reacts with a polymaleimide to fabricate robust heterogeneous polyurethane (PU) networks crosslinked through dynamic Diels-Alder (DA)/retro-DA chemistry. Promisingly, the fabricated PU network gels in which CNTs through rMDBC covalently embedded are flexible and robust to be bendable as well as exhibit self-healing elasticity and enhanced conductivity.