Thermal Characterization of Sexithiophenes Regioselectively Functionalized with Electron Donor Methylsulfanyl Groups

Abstract

The Differential Scanning Calorimetry (DSC) profile of a homogeneous series of regioregular β‐methylsulfanyl sexithiophenes, with different substitution patterns and number of substituents, is reported. The DSC data show that the thermal characteristics of these compounds strongly depend on the regiochemistry of substitution.

Order–disorder transitions in poly(3,4-ethylenedioxythiophene)

“…In oxidized conducting polymers it has been less commonly used and the few reports available suggest that the transitions measured are in fact irreversible decomposition of the material [19]. Oligomeric units of thiophenes have been successfully analysed using Differential Scanning Calorimetry (DSC) and have shown melting transitions around 306 C and transition energies of 115 J/g [20]. It would be expected that a highly ordered polymer should also have phase transitions between a crystalline and amorphous state.…”

“…The transition energies for PEDT were calculated for an entity of four repeat units plus a counter-ion (presuming a degree of doping of 0.25 as suggested by Aasmundtveit et al [15]), which gives energies in a range from 0.9 to 1.5 eV (this energy unit is necessary in order to compare with literature values for similar size units). Compared to the calculated and measured binding energies for crystalline quarto-thiophene (0.4 eV for the same entity [20]) e the data here suggest a very high degree of order in VPP PEDT which is lost during the phase transition observed by DSC and XRD. To determine whether these events are truly representing a thermodynamic phase transition or simply a decomposition reaction, as previously reported for polypyrrole [19], the reversibility of the transitions was examined.…”

“…In fact there is some indication of this second peak even in the other PEDT materials (in particular Cl À ). The energies of these transitions are all above 110 J/g, which is large compared to the melting transition in sexithiophene [20]. The transition energies for PEDT were calculated for an entity of four repeat units plus a counter-ion (presuming a degree of doping of 0.25 as suggested by Aasmundtveit et al [15]), which gives energies in a range from 0.9 to 1.5 eV (this energy unit is necessary in order to compare with literature values for similar size units).…”

Multiscale Self-Organization of the Organic Semiconductor α-Quinquethiophene

“…Thiophene oligomers can be regarded as one of the richest and more versatile systems for building organized structures across multiple length scales. They exhibit a variety of intra- and intermolecular interactions − van der Waals interactions, weak hydrogen bondings, π−π stacking, sulfur−sulfur interactions − all related to the “plasticity” of the thiophene ring,6a originating from the high polarizability of sulfur electrons. The “plasticity” of the thiophene ring, that is, the ability to adapt to the environment by ease of deformation of the bond angle and length, gives rise to a variety of conformations and packing motifs in the solid state, which are fascinating but unpredictable at the present state of knowledge.…”

“…The “plasticity” of the thiophene ring, that is, the ability to adapt to the environment by ease of deformation of the bond angle and length, gives rise to a variety of conformations and packing motifs in the solid state, which are fascinating but unpredictable at the present state of knowledge. Conformational polymorphism leads to different packing types for the same molecule and different optical properties for the bulk material. 6b,c Much has been learned about the self-organization properties of thiophene oligomers from single-crystal and powder X-ray diffraction data. ,, Among unsubstituted thiophene oligomers, single-crystal X-ray data have been reported for α-ter-, quater-, sexi-, and octithiophene . Thus, the great majority of the data reported on the solid-state supramolecular organization of unsubstituted oligothiophenes concerns even term compounds.…”