Interactions between surfactants and {1,4-phenylene-[9,9-bis(4-phenoxy-butylsulfonate)]fluorene-2,7-diyl}

The interaction between the water-soluble anionic conjugated copolymer poly{1,4-phenylene-[9,9-bis(4-phenoxy-butylsulfonate)]fluorene-2,7-diyl} (PBS-PFP) and various surfactants has been studied in aqueous solution by UV-vis absorption spectra, fluorescence and electrical conductivity. It is suggested from the linear dependence of absorbance, fluorescence and electrical conductivity on concentration that in the absence of surfactant, moderately stable dispersions are formed. These are affected in different ways on adding cationic, anionic or neutral surfactants. With the cationic cetyltrimethylammonium bromide, quenching of fluorescence intensity and lifetime, and formation of a new emission occurs at concentrations well below the critical micelle concentration (cmc). Electrical conductivity measurements indicate a discontinuity at surfactant/polymer ratio corresponding to electroneutrality, due to complexation. With the anionic sodium dodecyl sulfate, fluorescence quenching is also observed, but is attributed to formation of some mixed polymer/surfactant aggregate. The most striking changes are observed with the non-ionic pentaethyleneglycol monododecyl ether (C12E5), where a blue shift in fluorescence emission, dramatic increases in lifetime and quantum yield, and changes in electrical around the cmc are interpreted in terms of incorporation of single polymer chains in elongated cylindrical micelles. This is supported by 1H NMR spectroscopic measurements.http://www.sciencedirect.com/science/article/B6TFR-4GJK86Y-7/1/847da7ebe75424aac8aa097365af1c3

X-ray Raman scattering study of aligned polyfluorene

We present a non-resonant inelastic x-ray scattering study at the carbon K-edge on aligned poly[9,9-bis(2-ethylhexyl)-fluorene-2,7-diyl] and show that the x-ray Raman scattering technique can be used as a practical alternative to x-ray absorption measurements. We demonstrate that this novel method can be applied to studies on aligned $\pi$-conjugated polymers complementing diffraction and optical studies. Combining the experimental data and a very recently proposed theoretical scheme we demonstrate a unique property of x-ray Raman scattering by performing the symmetry decomposition on the density of unoccupied electronic states into $s$- and $p$-type symmetry contributions.Comment: 19 pages, 8 figure

International Consensus Statement on Rhinology and Allergy: Rhinosinusitis

Background: The 5 years since the publication of the first International Consensus Statement on Allergy and Rhinology: Rhinosinusitis (ICAR‐RS) has witnessed foundational progress in our understanding and treatment of rhinologic disease. These advances are reflected within the more than 40 new topics covered within the ICAR‐RS‐2021 as well as updates to the original 140 topics. This executive summary consolidates the evidence‐based findings of the document. Methods: ICAR‐RS presents over 180 topics in the forms of evidence‐based reviews with recommendations (EBRRs), evidence‐based reviews, and literature reviews. The highest grade structured recommendations of the EBRR sections are summarized in this executive summary. Results: ICAR‐RS‐2021 covers 22 topics regarding the medical management of RS, which are grade A/B and are presented in the executive summary. Additionally, 4 topics regarding the surgical management of RS are grade A/B and are presented in the executive summary. Finally, a comprehensive evidence‐based management algorithm is provided. Conclusion: This ICAR‐RS‐2021 executive summary provides a compilation of the evidence‐based recommendations for medical and surgical treatment of the most common forms of RS

Inter/intrachain interactions behind the formation of charge transfer states in polyspirobifluorene: A case study for complex excited-state dynamics in different polarity index solvents

In this work, we demonstrate the complex excited-state nature of the conjugated polymer, polyspirobifluorene (PSBF), using steady-state and time-resolved spectroscopy techniques to understand the origin of excited charge transfer state (CT) formation and their contribution to the total photoluminescence (PL). The measurements were compared in two solvents with different polarity, for example, methyl cyclohexane (MCH) and 2-methyltetrahydrofuran (2-MeTHF), which allow us to reveal solvent quality and temperature dependent CT state formation arising from “inter/intrachain” interaction phenomena. The inter/intrachain interactions are explained by means of spatial conformational changes of the polymer chain configuration, such as coiling and collapse of the backbone with concomitant side chain reorganization. It has been found that the PL emission at room temperature (RT) demonstrates a mixed state configuration containing contributions from 1(π, π*) excited states along with the CT states contribution, with the spectra arising from a mixture of the two emissive species. However, with decreasing temperatures to ca. 145 K (prior to the freezing point) in 2-MeTHF, the two emissive species become separated, with the emission from the CT state showing a red-shift with decreasing temperature. At 145 K, we observe the formation of an unstructured, wholly new emission band, which is strongly red-shifted relatively to the 1(π, π*) excited-state and shows classic Gaussian line shape. This emission is attributed to the formation of “inter/intrachain” CT states. In the case of frozen solutions (∼90 K), the spectra dramatically blue-shifts and loses all contribution from the “inter/intrachain” species, and emission then arises completely from the pure “intrachain” CT excitonic state. The behavior of the polymer is strongly dependent on both solvent quality and temperature effects on the excited state geometry relaxation by means of the local solvent–solute interactions that stabilize the CT states, due to solvation of the new charge distribution, and also changes on the transition states via manipulating energy barriers

Alternating Binaphthyl−Thiophene Copolymers: Synthesis, Spectroscopy, and Photophysics and Their Relevance to the Question of Energy Migration versus Conformational Relaxation

The synthesis and a comprehensive spectroscopic and photophysical study are presented of four alternating binaphthyl−oligothiophene copolymers (DP: 10−15 repeat units) in solution at room and low temperature and in the solid state (thin films). Detailed results are presented on absorption, emission, and triplet−triplet absorption spectra together with all relevant quantum yields (fluorescence, intersystem crossing, internal conversion, and singlet oxygen formation), excited-state lifetimes, and singlet and triplet energies. From these, several conclusions can be drawn. First, the main deactivation channels for the molecules in solution are the radiationless processes (S1 → S0 internal conversion and S1 → T1 intersystem crossing). Second, in the solid state the fluorescence quantum yields are smaller than those in solution. From time-resolved fluorescence decays in the picosecond time domain, three decay components are seen: a fast decay (40−60 ps) at short wavelengths, which becomes a rising component at longer wavelengths, an intermediate decay component (330−477 ps) associated with an ensemble of isolated segment-like units, which is dominant at the initial part of the emissive spectra and progressively decreases for longer emissions, and a third exponential related to the emission of the fully relaxed polymer. Together with steady-state anisotropy studies, this is discussed in terms of the possibilities of energy migration/transfer along the polymer chain and of the conformational (torsional) relaxation of the systems studied