Side-chain influence on the mass density and refractive index of polyfluorenes and star-shaped oligofluorene truxenes

This work is part of the TIRAMISU project, funded by the European Commission’s Seventh Framework Programme (FP7/2007-2013) under grant agreement n◦284747 and the Engineering and Physical Sciences Research Council (EPSRC) grants EP/J009016/1 and EP/F059922/1. I.D.W.S. and P.J.S. are Royal Society Wolfson Research Merit Award holders.The density of organic semiconductor films is an important quantity because it is related to intermolecular spacing which in turn determines the electronic and photophysical properties. We report thin film density and refractive index measurements of polyfluorenes and star-shaped oligofluorene truxene molecules. An ellipsometer and a procedure using a spectrophotometer were used to determine film thickness and mass of spin-coated films, respectively. We present a study of the effect of alkyl side-chain length on the volumetric mass density and refractive index of the materials studied. The density measured for poly(9,9-di-n-octylfluorene) (PF8) was 0.88 ± 0.04 g/cm3 and decreased with longer alkyl side chains. For the truxene molecule with butyl side chains (T3 butyl), we measured a density of 0.90 ± 0.04 g/cm3, which also decreased with increasing side-chain length.PostprintPeer reviewe

Security theory and practice: Energy security and environmental/climate protection in the second decade of the 21st century: Development trends

ZE WSTĘPU: W niniejszym tomie podjęte zostały aktualne zagadnienia związane z wybranymi aspektami bezpieczeństwa ekologicznego (w ujęciu przedmiotowym i narodowym), jak również implikacjami powiązania kwestii ochrony środowiska i klimatu z rozwojem społeczno-ekonomicznym oraz polityką i bezpieczeństwem energetycznym

Anti-SARS-CoV-2 Vaccination and PIMS-TS—Friends or Foe? Case Reports and Literature Review

Pediatric inflammatory, multisystem syndrome temporally associated with SARS-CoV-2 infection (PIMS-TS), also known as a multisystem inflammatory syndrome in children (MIS-C), is diagnosed in children who develop an inadequate inflammatory response after exposure to the SARS-CoV-2 virus. The pathogenesis of the abnormal response of the immune system to a previous SARS-COV-2 infection has not been explained. Similarly, the safety and effectiveness of COVID-19 vaccinations in this group of patients have become the subject of clinical discussion. Presenting experiences from many centers aims to answer this question. We present 4 cases of patients who suffered from PIMS-TS. Three of them were safely vaccinated against COVID-19 after illness. One patient developed PIMS-TS temporarily associated with COVID-19 vaccination. We also collected and discussed data from other centers

Subpicosecond exciton dynamics in polyfluorene films from experiment and microscopic theory

Electronic energy transfer (EET) in organic materials is a key mechanism that controls the efficiency of many processes, including light harvesting antennas in natural and artificial photosynthesis, organic solar cells, and biological systems. In this paper we have examined EET in solid-state thin-films of polyfluorene, a prototypical conjugated polymer, with ultrafast photoluminescence experiments and theoretical modeling. We observe EET occurring on a 680 ± 300 fs time scale by looking at the depolarisation of photoluminescence. An independent, predictive microscopic theoretical model is built by defining 125 000 chromophores containing both spatial and energetic disorder appropriate for a spin-coated thin film. The model predicts time-dependent exciton dynamics, without any fitting parameters, using the incoherent Förster-type hopping model. Electronic coupling between the chromophores is calculated by an improved version of the usual line-dipole model for resonant energy transfer. Without the need for higher level interactions, we find that the model is in general agreement with the experimentally observed 680 ± 300 fs depolarisation caused by EET. This leads us to conclude that femtosecond EET in polyfluorene can be described well by conventional resonant energy transfer, as long as the relevant microscopic parameters are well captured. The implications of this finding are that dipole-dipole resonant energy transfer can in some circumstances be fully adequate to describe ultrafast EET without needing to invoke strong or intermediate coupling mechanisms

Side-chain influence on the mass density and refractive index of polyfluorenes and star-shaped oligofluorene truxenes

The density of organic semiconductor films is an important quantity because it is related to intermolecular spacing which in turn determines the electronic and photophysical properties. We report thin film density and refractive index measurements of polyfluorenes and star-shaped oligofluorene truxene molecules. An ellipsometer and a procedure using a spectrophotometer were used to determine film thickness and mass of spin-coated films, respectively. We present a study of the effect of alkyl side-chain length on the volumetric mass density and refractive index of the materials studied. The density measured for poly(9,9-di-n-octylfluorene) (PF8) was 0.88 ± 0.04 g/cm3 and decreased with longer alkyl side chains. For the truxene molecule with butyl side chains (T3 butyl), we measured a density of 0.90 ± 0.04 g/cm3, which also decreased with increasing side-chain length