Abstract Ladder‐type pentaphenyl chromophores have a rigid, planar π‐system and show bright fluorescence featuring pronounced vibrational structure. Such moieties are ideal for studying interchromophoric interactions and delocalization of electronic excitations. We report the synthesis of helical polymers with a rigid square structure based on spiro‐linked ladder‐type pentaphenyl units. The variation of circular dichroism with increasing chain length provides direct evidence for delocalization of electronic excitations over at least 10 monomeric units. The change in the degree of circular polarization of the fluorescence across the vibronic side bands shows that vibrational motion can localize the excitation dynamically to almost one single unit through breakdown of the Born‐Oppenheimer approximation. The dynamic conversion between delocalized and localized excited states provides a new paradigm for interpreting circular dichroism in helical polymers such as proteins and polynucleic acids.

Organic electrochemical transistors (ECTs) are an important building block for bioelectronics. To promote the required ion transport through the active layer, state-of-the-art semiconducting polymers feature hydrophilic ethylene glycol side chains that increase the volumetric capacitance and transconductance of the devices. Here, we apply this concept to polymer-wrapped single-walled carbon nanotubes (SWCNTs) as a high-mobility semiconducting material. We replace the polyfluorene copolymer (PFO-BPy), which is used for selectively dispersing semiconducting (6,5) SWCNTs and contains octyl side chains, by an equivalent polymer with tetraethylene glycol side chains. Aerosol-jet printed networks of these SWCNTs are applied as the active layer in water-gated ECTs. These show high hole mobilities (3-15 cm2·V-1·s-1), significantly improved volumetric capacitances and larger transconductances. Thin networks of SWCNTs reach (219 ± 16) F·cm-1·V-1·s-1 as the product of mobility and volumetric capacitance. In situ photoluminescence measurements show more efficient quenching of the near-infrared fluorescence for nanotube networks with hydrophilic glycol side chains compared to those with hydrophobic alkyl side chains, thus corroborating more complete charging under bias. Overall, networks of semiconducting SWCNTs with such tailored wrapping polymers provide excellent device performance. Combined with their inherent mechanical flexibility and durability, they constitute a competitive material for bioelectronics.

Neuromorphic devices are likely to be the next evolution of computing, allowing to implement machine learning within hardware components. In biological neural systems, learning and signal processing are achieved by communication between neurons through time‐dependent ion flux in the synapses. Integrating such ion‐mediated operating principles in neuromorphic devices can deliver an energy efficient and powerful technology. Here a device known as a light‐emitting electrochemical cell is revisited and modified, exploiting its ability to modulate current through ion accumulation/depletion at the electrodes and turn it into an organic synaptic diode. This two‐terminal device is based on an organic mixed ionic‐electronic conducting polymer that serves as active layer for conduction of lithium ions as well as charge carriers. The ionic conduction properties are modified by cryptand molecules, able to reversibly capture ions. The device can be reliably switched between states for at least 100 cycles and displays state retention for multiple minutes. The applicability for neuromorphic applications is further demonstrated by exploring frequency‐dependent plasticity and paired‐pulse facilitation behavior in the millisecond range. The polymeric nature, combined with the simple two‐terminal architecture of the presented neuromorphic device, opens up a range of possibilities regarding the fabrication of artificial neural networks.

The fluorescence behavior of a PNIPAM-grafted polyfluorene copolymer (PF-PNIPAM) together with the corresponding precursor polymer (9,9-bis(.-carboxypentyl)-substituted polyfluorene, PF-COOEt) was investigated by UV-Vis spectroscopy and steady-state and time-resolved fluorescence techniques in DMF and in an acetone:water (1:2) mixture over the temperature range 5 to 70 degrees C. Temperature dependence plots show a clearly different behavior in the acetone:water (1:2) mixture, which, based on the overall data, is attributed to the occurrence of a lower critical solution temperature (LCST) for PF-PNIPAM, which is found at similar to 45 degrees C, different from the value for PNIPAM chains in water of similar to 32 degrees C. In the acetone:water (1:2) mixture, the weak temperature dependence of the fluorescence decay time components between 20 and 70 degrees C documents a dominant intra- and interchain hopping-type deactivation mechanism. However, additionally, the thermoresponsive PNIPAM side chains cause aggregate formation at the LCST temperature coupled to abrupt changes of the fluorescence intensity. Dynamic light scattering (DLS) studies for PF-PNIPAM also in the acetone:water (1:2) mixture in the temperature range of 20-55 degrees C show for T > 40 degrees C a unimodal size distribution peaking for diameters of >200 nm corresponding to aggregates, contrasting to a bimodal distribution with lower hydrodynamic radii at lower temperatures. The study delivers additional information to the puzzling LCST behavior of PNIPAM-based (co)polymers, which in PF-PNIPAM impacts the presence of both polyfluorene PF main chains and PNIPAM side chains.

The design of new arylated poly(phenylene vinylene) with high fluorescence efficiency (from AIE) and intrinsic microporosity (from SBET) is described.

Nanohybrids of purified semiconducting single-walled carbon nanotubes and conjugated polymers with attached spiropyran moieties are created as photoresponsive materials for optical memory devices and ultraviolet (UV) light sensors. The hybrids respond to UV light exposure in air with photoisomerization of the spiropyran groups to merocyanine, resulting in significant and persistent p-doping of the nanotubes, as confirmed by photoluminescence quenching and trion emission. The increased carrier concentration after illumination and the inherently high mobility of carbon nanotubes enable an up to two orders of magnitude increased conductivity of the nanotube/polymer hybrid networks in simple two-terminal devices operated at very low bias. The photodoping decays very slowly in the dark and increases further with every illumination dose. However, it can be completely reversed by heating for a few seconds. Thin film devices based on these photoresponsive polymer/nanotube hybrids show great potential as simple and resettable UV dosimeters and optical memory elements.

Conjugated polymers exhibit strong interactions with single-walled carbon nanotubes (SWNTs). These enable the selective dispersion of specific semiconducting SWNTs in organic solvents and polymer-mediated energy transfer to the nanotubes followed by emission in the near-infrared. Conjugated polyelectrolytes with ionic side-chains can add further functionalities to these nanotube/polymer hybrids such as dispersibility in polar solvents (e.g., methanol) and self-doping. Here, we demonstrate and investigate energy transfer from a range of conjugated polymers to preselected (6,5) SWNTs with varying spectral overlap between the optical transitions of the polymer and nanotube. We find evidence for increased backbone planarization of the polymers wrapped around the nanotubes. Furthermore, ambient p-doping of hybrids of anionic conjugated polyelectrolytes and (6,5) SWNTs blocks energy transfer in contrast to cationic polyelectrolytes. By addition of a mild reducing agent, thus removing the p-doping, the energy transfer can be fully restored pointing toward an electron exchange mechanism. The p-doping of nanotube/polyelectrolyte hybrids in air and their doping-dependent emission and charge transport properties also become apparent in water-gated field-effect transistors based on such networks and might be useful for dual-signal sensing applications.

Incorporation of tetrabenzohepta- or -pentafulvalene connectors into soluble, aromatic polymers results in significantly different optical spectra and intrinsic microporosity.

The aggregation-induced emission（AIE） phenomenon provides a new direction for the development of organic light-emitting devices. Here, we present a new class of emitters based on 4,4-difluoro-4-bora-3 a,4 a-diaza-s-indacene（BODIPY）, functionalized at different positions with tetraphenylethylene（TPE）, which is one of the most famous AIE luminogens. Thanks to this modification, we were able to tune the photoluminescence of the BODIPY moiety from the green to the near-infrared（NIR）spectral range and achieve PL efficiencies of 5 0% in the solid state. Remarkably, we observed an enhancement of the AIE and up to 1 00% photoluminescence efficiencies by blending the TPE-substituted BODIPY fluorophores with a poly[（9,9-di-noctylfluorene-2,7-diyl）-alt-（benzo[2,1,3]thiadiazol-4,7-diyl）]（F8 BT） matrix. By incorporating these blends in organic lightemitting diodes（OLEDs）, we obtained electroluminescence peaked in the range 650–700 nm with up to 1.8% external quantum efficiency and 2 m W/cm2 radiance, a remarkable result for red/NIR emitting and solution-processed OLEDs.