In 1995 we extrapolated the so-called “effective conjugation length” in (para-phenylene) ladder polymers by relating the optical absorption energy to the reciprocal chain length of ladder-type oligo-(para-phenylene)s, but only based on three short-chain oligomers (a trimer, a pentamer, and a heptamer). The resulting value of 11–12 benzene rings was distinctly lower than the numbers reported for corresponding single-stranded, soluble poly(para-phenylene)s. Here, we report a series of elongated (para-phenylene)-type ladder oligomers that were isolated via repeated recycling size exclusion chromatography steps from an oligomer mixture. Now we are able to extrapolate the length of the “effectively conjugated segment” with much more precision to be 19 ± 2 benzene rings.

We study relations among the side-chain asymmetry, structure, and order-disorder transition (ODT) in hairy-rod-type poly(9,9-dihexylfluorene) (PF6) with two identical side chains and atactic poly(9-octyl-9-methyl-fluorene) (PF1-8) with two different side chains per repeat. PF6 and PF1-8 organize into alternating side-chain and backbone layers that transform into an isotropic phase at T^{ODT}(PF6) and T_{bi}^{ODT}(PF1-8). We interpret polymers in terms of monodisperse and bidisperse brushes and predict scenarios T^{ODT}<T_{bi}^{ODT} and T^{ODT}∼T_{bi}^{ODT} for high and low grafting densities (the side-chain length above or below the average grafting distance). Calorimetry and x-ray scattering indicate the condition T^{ODT}(PF6)∼T_{bi}^{ODT}(PF1-8) following the low grafting prediction. PF6 side chains coming from the alternating backbone layers appear as two separate layers with thickness H(PF6), whereas PF1-8 side chains appear as an indistinguishable bilayer with a half thickness H_{bilayer}(PF1-8)/2≈H(PF6). The low grafting density region is structurally possible but not certain for PF6 and confirmed for PF1-8.

The morphology of highly regular, semi-crystalline P3HT (poly 3-hexylthiophene-2.5-diyl) after thermal nanoimprint is studied and compared to that of its amorphous counterpart. Differential scanning calorimetry measurements of both materials provide the glass transition temperature (below room temperature) as well as the melting temperature (T m ≈ 235 °C) and the crystallization temperature (T c ≈ 200 °C) of the semi-crystalline polymer. Imprint experiments are performed at temperatures below and above the melting temperature of the crystallites. The samples imprinted with line structures in the range of 135–500 nm are investigated by scanning electron microscopy and transmission measurements. In agreement with T m, the investigations indicate that the crystallites do not melt when semi-crystalline P3HT is imprinted below T m. After imprint above T m, no more indication of the crystallites is found. Furthermore, physical self-assembly only occurred after imprint beyond T m with semi-crystalline P3HT, indicating a fully amorphous state. The morphology observed—the roughness of the surface within partly filled cavities when crystallites are present—correlates well with the results from optical measurements.

Both hyperbranched polymers and dendrimers as densely branched macromolecules contain a large number of terminal groups (end groups). The condensation of monomers with two or more different functionalities (average functionality > 2; commonly denoted AB2, AB3, A3 + B2, etc.) creates (hyper) branched structures with an exponential growth of both endgroup number and molecular weight. Dendrimers are by definition monodisperse hyperbranched macromolecules, while so-called hyperbranched polymers are polydisperse. Dendrimer synthesis requires a full control over all synthesis steps, often accomplished in repetitive condensation/deprotection cycles. Contrarily, the generation of hyperbranched polymers is generally possible in much simpler, one-step approaches.[1] Reacting rigid, aromatic monomers allows the generation of dimensionally stable, hyperbranched polyarylenes.[2–7] The decoration of their terminal positions (end caps) with functional building blocks (chromophores, conjugated oligomers, or polymers) enables the generation of multifunctional polymers with a large number of terminal groups and a defined spatial arrangement of core and tail components. Such a synthetic route allows the generation of a series of structurally related hyperbranched polymers with similar backbones but different end groups thus tailoring the physical, optical, or electronic properties of the target structures. Truxene-cored, hyperbranched or star-shaped macromolecules for blue light emission have been described in a number of reports.[8–11] Moreover, Pei et al. have reported the synthesis and optical properties of star-shaped truxene-oligothiophene systems.[12] We have now synthesized two AB2-type truxene monomers and coupled them in a Suzuki cross-coupling polycondensation scheme to generate novel rigid, hyperbranched polytruxene scaffolds that are pre-built for a subsequent decoration with functional tails (in an AB2 + A approach). For that, we have used different monofunctional chromophoric moieties (low-molecular-weight chromophores) as well as monofunctional polythiophene blocks as end cappers. Subsequently, we have studied the excitation energy transfer from the blue emitting, hyperbranched polytruxene core to the various terminal chromophores (low-molecular-weight or polymeric chromophores)

Novel dye-terminated, hyperbranched polytruxenes and polytruxene-block-polythiophene multiblock copolymers have been synthesized in a simple “AB2 + A” approach. Photoexcitation into the higher energy polytruxene absorption band results in an efficient excitation energy transfer to the peripheral dye or polythiophene blocks.

Abstract A series of new π-conjugated donor-acceptor copolymers, based on a naphthalene-bisimide moiety as the electron-acceptor and connected to either thiophene or dialkylfluorene as the electron-donor, were synthesized. The polymers are soluble in common organic solvents. The UV-Vis spectra of the copolymers in chloroform showed two absorption maxima at higher energies (ca. 301 - 364 nm), assigned to the π-π * transition, and at a lower energy (ca. 512 - 595 nm), ascribed to the intramolecular charge transfer between donor and acceptor units. Cyclic voltammetry revealed that the polymers were susceptible to both electrochemical oxidation and reduction, and they had a LUMO and HOMO levels ranging from -4.07 to -3.80 eV and -6.13 to -5.64 eV, respectively. The energy band gaps were estimated to be 1.48 - 2.06 eV. These results represent a positive step towards making novel compounds suitable for electronic applications.

Novel, all-conjugated polyelectrolyte block copolymers of the rod-rod type can be generated in a "grafting from'' scheme and exhibit a preferred tendency to self-assemble into layered aggregates both in solution and the solid state. Here, the rigid-rod structure of the individual, complex macromolecules favours the formation of low-curvature vesicular and lamellar aggregates. Our poly(9,9-dialkylfluorene)-b-poly[3-(6-ammoniumhexyl)thiophene](PF2/6-b-P3TMAHT and PFO-b-P3TMAHT, where PF2/6 and PFO denote 2-(ethyl) hexyl and linear octyl alkyl pendant groups, respectively), and poly(9,9-dialkylfluorene)-b-poly[3-(6-pyridylhexyl) thiophene] (PF2/6-b-P3PyHT and PFO-b-P3PyHT) polyelectrolyte diblock copolymers allow for simple and reliable control of the occurring self-organisation process and the resulting nano-scaled architectures. They are, therefore, promising candidates for application as the active layer in electronic devices or as functional membranes (e. g. for sensor applications). Moreover, the electronic properties of the materials (especially the excitation energy transfer between both blocks) strongly depend on the aggregation state present. Aggregation can be further controlled via addition of oppositely charged surfactants resulting in the formation of ordered polyelectrolyte/surfactant complexes.

In this manuscript, non-classical nonvertical triplet acceptors are proposed as a promising class of efficient triplet scavengers for future solid-state electrically pumped organic lasers. Triplet excitation scavenging is investigated in polymer films of polyfluorene, a prospective material for the fabrication of thin-film organic lasers. Two dopant molecules, cyclooctatetraene (COT, a nonvertical triplet acceptor) and anthracene (a vertical triplet acceptor), are studied and the occurrence of anomalous nonvertical triplet energy transfer in solid conjugated polymer films is demonstrated for the first time employing COT.

Phosphorescence and delayed fluorescence of polyfluorene polymer films doped with cyclooctatetraene (COT) and anthracene are studied by means of time-resolved photoluminescence (PL) measurements. The occurrence of an anomalous nonvertical triplet energy transfer in solid conjugated polymer films is demonstrated for the first time employing the "nonvertical" COT triplet acceptor, which appears to behave similarly to conventional vertical triplet acceptors, such as anthracene. Both dopant molecules are found to efficiently quench the host phosphorescence of the polymer without affecting the host fluorescence--this can be attributed to the large singlet-triplet (S(1)-T(1)) splitting of these molecules. This S(1)-T(1) splitting is exceptionally large in COT due to its low-lying relaxed triplet state, which is capable of accepting host triplet excitations. In contrast to anthracene, the triplet lifetime of the COT molecules is reasonably short, thus making a fast deactivation of the triplet excitations possible. This suggests that nonvertical triplet scavengers might be promising candidates for quenching the host triplet excitations in future electrically pumped fluorescence organic lasers, which suffer from excessive triplet-state losses.