Direct evidence of the failure of electric-dipole approximation in second-harmonic generation from a chiral polymer film

Second-harmonic generation from Langmuir-Blodgett films of a polythiophene is strongly influenced by the chirality of the polymer. The polarization dependence of the process cannot be explained in the elec.-dipole approxn. Evidence of contributions beyond elec. dipoles is obtained directly from individual second-harmonic signal

Polymeeroppervlakken : structuur en dynamica van polymeeroppervlakken en -grenslagen

No abstract

On the origin of optical activity in polythiophenes

Optically active substituents attached as sidechain to p-conjugated polymers provide a particularly interesting and revealing tool to study the nanoscopic and mesoscopic supramolecular organization of p-conjugated polymers in general. Chiral substituents allow the properties of these polymers to be studied with circularly polarized light in both absorption and emission. Here we describe a comprehensive investigation on the structure and optical properties of poly{3,4-bis[(S)-2-methylbutoxy]thiophene} (PBMBT) as an example to elucidate the molecular origin of the chiroptical effects in chiral conjugated polymers. The chiral side chains of PBMBT induce very strong bisignate circular dichroism (CD) effects in the p–p* absorption when the polymer is in an aggregated phase. The anisotropy factor in absorption (gabs) is as high as 8×10-2. The photoluminescence of PBMBT aggregates is characterized by a very small Stokes shift

Thermochromism in the triplet excited state of poly(3-octylthiophene)

Aggregation of poly(3-octylthiophene) (P3OT) in 2-methyltetrahydrofuran (2MeTHF) at low temperature results in ordered microcrystallites which exhibit a red-shifted triplet-triplet absorption spectrum in comparison with molecularly dissolved chains