A chiral poly(para-phenyleneethynylene) (PPE) derivative

Fiesel, Rainer; Scherf, Ullrich

doi:10.1002/marc.1998.030190806

Cited by 15 publications

(29 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In very dilute chloroform solution (<10 -2 mg/L), the emission spectra 17 of 1a,b,d show a sharp feature at 425 nm and a second one of lower intensity at 450 nm, in perfect accord with literature observations. [11][12][13] In the case of 1c the shoulder is observed at 440 nm. The fluorescence quantum yield of all examined polymers 1a-d in solution is unity.…”

Section: Resultsmentioning

confidence: 99%

“…Aggregate formation and concomitant change of structure is not well understood in alkoxy-substituted PPEs. 11b According to a recent study by Fiesel and Scherf, 13 alkoxy-substituted PPEs do not display solvatochromism in chloroform/methanol mixtures, as was evidenced by the unchanged UV-vis spectra. The examination of the absorptive and emissive behavior of 1a-d in chloroform, chloroform/methanol solutions, and in the solid state, however, corroborates the presence of aggregates in the mixed chloroform/methanol solvent and in thin films.…”

Section: Discussionmentioning

confidence: 97%

“…While excimer and aggregate formation in the PPV case is under intense scrutiny,7b the related poly( p- phenyleneethynylenes) have found less interest in the past but are becoming increasingly popular. − From the beginning, the high fluorescence quantum yields of PPEs in solution recommended them as attractive candidates for optical applications in emitting organic devices. It has been noted that thin films of alkoxy-substituted PPEs can display some bathochromic shift in their absorption spectra when compared to those for dilute solutions, but the phenomenon has not been studied systematically and no data for the electronically unperturbed (but thermally more stable) dialkyl-substituted derivatives of 1 are available.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Evidence of Aggregate Formation for 2,5-Dialkylpoly(p-phenyleneethynylenes) in Solution and Thin Films

et al. 1998

View full text Add to dashboard Cite

The absorptive and emissive behavior of four highly fluorescent bisalkyl-substituted poly(p-phenyleneethynylenes) (R = hexyl, dodecyl, 2-(ethyl)hexyl, and 3,5,5-trimethylhexyl) was examined. Aggregate and excimer formation was seen in solution and in the solid state by a combination of absorption and fluorescence spectroscopy in solvent/nonsolvent (chloroform/methanol) mixtures and in thin films. The aggregates were identified by the occurrence of a sharp absorption centered at 440 nm, undetectable in dilute chloroform solution, and a broad emission at 504 nm. The average size of the aggregate formed in chloroform/methanol solvent mixtures must exceed 1.5 μm, as was evidenced in filtering-experiments utilizing a set of membranes with different pore sizes to successively remove smaller aggregates.

show abstract

Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Evidence of Aggregate Formation for 2,5-Dialkylpoly(p-phenyleneethynylenes) in Solution and Thin Films

et al. 1998

View full text Add to dashboard Cite

show abstract

“…Phenylene ethynylene architectures have proven to be a rich platform on which to conduct supramolecular and nanoscale chemistry. 1,2 Representative examples as shown in Chart 1 include hexameric macrocycles, [3][4][5][6][7] para-linked rigid rod segments, [8][9][10][11][12][13][14][15] and the more conformationally diverse ortho-and meta-linked oligomers. [16][17][18][19][20] A summary of their observed supramolecular behavior can be gleaned from Figure 1.…”

Section: Introductionmentioning

confidence: 99%

Supramolecular Organization of Oligo(m-phenylene ethynylene)s in the Solid-State

1999

View full text Add to dashboard Cite

A series of oligo(m-phenylene ethylene)s having triethylene glycol ester-linked side chains (i.e., 2-[2-(2-methoxyethoxy)ethoxy]ethyl esters) were prepared, and their supramolecular organization in the solid-state was studied. These oligomers are amphiphilic, having a nonpolar aromatic hydrocarbon backbone that is appended with flexible polar side chains. Oligomers containing eight or more monomers are viscoelastic waxy solids at room temperature, exhibiting birefringent textures that reversibly melt into isotropic fluids upon warming. As the chain length increases, the materials stiffen and the melting point rises asymptotically, suggesting homologous packing for all members of the series. These observations are in accord with the behavior of conventional short-chain polymers, whereby melting point depression results from the volume fraction of chain ends. Small- and wide-angle X-ray diffraction investigations were carried out to elucidate the details of chain packing. Samples slowly cooled from the isotropic melt develop lamellar organizations with longitudinal spacings that depend linearly on the chain length. The relationship between the calculated repeat unit length and the experimentally observed increment in lamellar spacing per repeat unit suggests that the chains are oriented 30° from the layer normal. Macroscopically aligned samples showed two sets of mutually orthogonal lateral reflections whose d-spacings are nearly independent of chain length. A model for the solid-state organization of these oligomers is proposed. Solution- and solid-state UV spectra are presented and interpreted by considering the relative abundance of cisoid vs transoid conformers under these various conditions.

show abstract

“…However, thin films of chiral PPEs have also been widely characterized by chiroptical spectroscopies. The first chiroptical investigation of PPEs as thin films was reported by Scherf et al; drop-casted samples from CHCl 3 solution of the enantiopure poly(2,5-bis[(S)-2-methylbutoxy]-1,4-phenyleneethynylene) exhibited a maximum g abs value of ∼0.001 at 476 nm,666 while for thin films of the chiral poly(2,5-bis[(S)-3,7-dimethyloctyl]-1,4-phenyleneethynylene), prepared under the same conditions, a g abs value of 1.3 × 10 −2 (at 432 nm) was found 667. In 2002, Neher and Bunz studied the statistical copolymers 77a−c, containing the enantiopure 2,5-bis[(S)-3,7dimethyloctyl]-p-phenyleneethynylene and the racemic 2,5bis[(rac)-2-ethylhexyl]-p-phenyleneethynylene units in different ratios; surprisingly, spin-casted films from CHCl 3 solution of the copolymers 77b and 77c, after thermal annealing for 30 s at 160 °C (just below their liquid crystal/isotropic transition) and for other 2 h at 140 °C, revealed the very large g abs values (at 432 nm) of −0.292 and −0.378, respectively (Figure…”

mentioning

confidence: 99%

Chiroptical Properties in Thin Films of π-Conjugated Systems

2020

View full text Add to dashboard Cite

Chiral π-conjugated molecules provide new materials with outstanding features for current and perspective applications, especially in the field of optoelectronic devices. In thin films, processes such as charge conduction, light absorption, and emission are governed not only by the structure of the individual molecules but also by their supramolecular structures and intermolecular interactions to a large extent. Electronic circular dichroism, ECD, and its emission counterpart, circularly polarized luminescence, CPL, provide tools for studying aggregated states and the key properties to be sought for designing innovative devices. In this review, we shall present a comprehensive coverage of chiroptical properties measured on thin films of organic π-conjugated molecules. In the first part, we shall discuss some general concepts of ECD, CPL, and other chiroptical spectroscopies, with a focus on their applications to thin film samples. In the following, we will overview the existing literature on chiral π-conjugated systems whose thin films have been characterized by ECD and/or CPL, as well other chiroptical spectroscopies. Special emphasis will be put on systems with large dissymmetry factors (g abs and g lum) and on the application of ECD and CPL to derive structural information on aggregated states.

show abstract

A chiral poly(para-phenyleneethynylene) (PPE) derivative

Cited by 15 publications

References 0 publications

Evidence of Aggregate Formation for 2,5-Dialkylpoly(p-phenyleneethynylenes) in Solution and Thin Films

Evidence of Aggregate Formation for 2,5-Dialkylpoly(p-phenyleneethynylenes) in Solution and Thin Films

Supramolecular Organization of Oligo(m-phenylene ethynylene)s in the Solid-State

Chiroptical Properties in Thin Films of π-Conjugated Systems

Contact Info

Product

Resources

About