6 research outputs found
Climate Change 2014: Impacts,Adaptation, and Vulnerability. Part A: Global and Sectoral Aspects. Contribution of Working Group II to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change
Effect of Molecular Structure of α,α′-Dialkylquaterthiophenes and Their Organosilicon Multipods on Ordering, Phase Behavior, and Charge Carrier Mobility
We report on bulk structures of a family of quaterthiophene
(<b>4T</b>) derivatives with linear and branched end groups
such as
α,α′-dihexylquaterthiophene (<b>Hex-4T-Hex</b>), α,α′-didecyl-quaterthiophene (<b>Dec-4T-Dec</b>) and α,α′-bisÂ(2-ethylhexyl)Âquaterthiophene (<b>EH-4T-EH</b>), tetramethyldisiloxane-based dimers <b>D2-Und-4T-EH</b> and <b>D2-Und-4T-Hex</b>, and carbosilane-siloxane-based tetramers <b>D4-Und-4T-EH</b> and <b>D4-Und-4T-Hex</b>. The dimers and
tetramers contain undecylenic (<b>Und</b>) spacers between the
disiloxane and <b>4T</b>- units of the molecule. The impact
of the molecular architecture on the bulk structure at different temperatures
is addressed with X-ray diffraction and differential scanning calorimetry.
For all of the studied quaterthiophene-containing organosilicon multipods
the formation of <b>4T</b>-crystal sublattice is observed. The
alkyl periphery plays an important role in the molecular packing and
thermal stability of the ordered phase. They can stabilize or destabilize
the crystal phase, depending on their length and architecture. The
quaterthiophenes with 2-ethylhexyl end groups adopt a zig-zag conformation
in the crystalline state at room temperature. This change of conformation
leads to a significant decrease of the polymorphic transition and
isotropization temperatures. The efficiency of <b>4T</b> packing
in the sublattice is estimated from the molecular cross-section (S)
in the plane normal to the molecular axis. Correlations between S
and field-effect charge carrier mobility are established