Solution spectroscopic properties of polyDCHD-HS: a novel highly soluble polydiacetylene

Abstract

The solution properties of a novel soluble polydiacetylene, poly[1,6-bis(3,6-dihexadecyl-9H-carbazol-9-yl)hexa-\ud 2,4-diyne] (polyDCHD-HS), have been investigated by using UV–Vis absorption, fluorescence, and FT-Raman\ud spectroscopies. The polymer gives rise to stable, brilliant red solutions in aromatic solvents and in chloroform at\ud room temperature with no evidence of the colour transition to yellow that usually takes place by increasing the\ud temperature with other soluble polydiacetylenes. A particular role appears to be played by benzene–polyDCHD-HS\ud interactions, because in this solvent a very narrow and intense excitonic peak is observed at room temperature in the\ud electronic spectrum. Interestingly, these solutions show also a well-resolved fluorescence spectrum, with a very small\ud Stokes shift and a rather high quantum yield (≅102). Furthermore, a very efficient transfer of the excitation energy\ud from the carbazolyl substituents to the conjugated backbone is found to take place. On account of the observation\ud that by increasing the temperature of the benzene solutions up to 75 C the excitonic feature in both the absorption\ud and the emission spectra undergoes fully reversible broadening and intensity reduction accompanied by the increase\ud of the Stokes shift, without any dramatic colour change, it is likely that the rates of torsional motions in the polymer\ud chains are thermally activated without modifying the average conjugation length of the polymer chains. FT-Raman\ud measurements in benzene solutions in the same temperature range have confirmed this conclusion. The photophysical\ud properties of polyDCHD-HS in benzene around 60 C are quite similar to those observed in other aromatic solvents\ud at room temperature. By heating up the red solutions in toluene or in chlorobenzene, no spectral shift is observed but\ud only a limited increase of the absorption band broadening. All these findings strongly suggest that by the appropriate\ud choice of the substituents it is possible to obtain stable solutions of the red form of polydiacetylenes

Optical Studies of Artificial Opals as 3D Photonic Crystals

“…The spectrum of the solution, discussed in detail in ref. [6], is also reported for comparison. Even though these data are very preliminary some conclusion can be drawn.…”

“…The films are used as grown without any annealing. Poly[1,6-bis(3,6-dihexadecyl-9H-carbazolyl-9-yl)hexa-2,4-diyne] (poly(DCHD-HS)) was prepared according to [6]. Atomic force microscopy (AFM) was performed by a Digital Instrument model NanoScope 3100 microscope in tapping mode.…”

Triplet excitons in acyl- and alkyl-substituted polycarbazolyldiacetylenes: A spectroscopical and photophysical study

“…However, for polyDCHD-HS in benzene solution, i.e., when sharp absorption features and low el-ph coupling are observed, the emission efficiency increases up to about 1%. 27 The different efficiency is probably related to the ordering of the first excited states for the polymers in different environments. An extensive investigation of the excited states of polyDCHD-HS allowed us to show that in the solid state, when the polymer is nonfluorescent, the first excited state of 2A g symmetry 10,11 lies about 0.2 eV below the 1B u state while in benzene solution, where luminescence is detected, 28 the lowest excited state of 1B u symmetry lies about 0.03 eV below the 2A g state, thus explaining its unusual emission properties.…”

Real-time observation of coherent nuclear motion in polydiacetylene isolated chains

“…The emission quantum yield is estimated to be 10 Ϫ2 . 14 Based on previously reported transient transmission difference measurements on polyDCHD-HS ͑Ref. 15͒ in C 6 H 6 solution, the following picture, also sketched in Fig.…”

“…11,12 We study a substituted PDA, namely, poly͓1,6-bis͑3,6-dihexadecyl-N-carbazolyl͒-2,4-hexadiyne͔ ͑polyDCHD-HS͒ ͑Ref. 13͒; PolyDCHD-HS is soluble in common organic solvents and in benzene it displays an astonishingly sharp and intense room temperature excitonic resonance, 14 indicative of a highly ordered material and negligible interchain interactions. In a previous report 15 we discussed population relaxation in PolyDCHD-HS, here we focus on the vibrational dynamics of this system following excitation with sub-10-fs pulses, which allows one to generate and probe vibrational wave packet motion onto ground and excited potential energy surfaces.…”