41 research outputs found
Nanomechanical properties of molecular-scale bridges as visualised by intramolecular electronic energy transfer
Relationship between morphology, properties and degradation parameters of novative biobased thermoplastic polyurethanes obtained from dimer fatty acids
Biobased thermoplastic polyurethanes (TPUs) obtained from dimer acid-based polyols, 4,40-diphenyl- methane diisocyanate and 1,4-butanediol were synthesised by using a two-step prepolymer process. The effect of dimer acid-based polyols on the processing parameters was investigated. A full thermal, mechanical and thermo-mechanical characterisation of TPUs synthesised with different hard segment (HS) contents was also carried out. Thermogravimetric analysis showed the presence of three degra- dation steps which varied between the different TPU structures depending on the HS content. Colour tests showed substantial differences between TPU samples which were related to degradation param- eters. Initial degradation temperatures were lower than the polyol's one and decreased with increasing HS contents. Tensile tests showed high deformation at break for these elastomeric TPU samples, except for the sample with 40 wt% of HS. Finally, rheology studies revealed that the melting temperature generally decreased with higher HS content
Triplet State Formation in Homo- and Heterometallic Diketopyrrolopyrrole Chromophores
The
synthesis, structural characterization, and excited-state dynamics
of series of diketopyrrolopyrrole (DPP) bridged homodinuclear IrÂ(III)
and heterodinuclear IrÂ(III)/PtÂ(II) complexes is described. Steady-state
and time-resolved photoluminescence along with transient absorption
measurements were used to probe the nature of the emissive and long-lived
excited states. Upon excitation into the <sup>1</sup>DPP ligand-localized excited state in the presence of coordinated
IrÂ(III) or PtÂ(II) metal centers, the intersystem crossing is enhanced,
leading to a quenching of the <sup>1</sup>DPP fluorescence and the
formation of the long-lived (τ ≈ 30–40 μs) <sup>3</sup>DPP excited state in all instances