Poly blue shift

There have been very few examples of PTV derivatives substituted at the vinylene position. One example poly(2,5-thienylene-1,2-dimethoxy-ethenylene) 102 has been documented by Geise and co-workers and its synthesis is outlined in Scheme 1-32 [133]. Thiophene-2,5-dicarboxaldehyde 99 is polymerized using a benzoin condensation the polyacyloin precursor 100 was treated with base to obtain polydianion 101. Subsequent treatment with dimethyl sulfate affords 102, which is soluble in solvents such as chloroform, methanol, and DMF. The molar mass of the polymer obtained is rather low (M = 1010) and its band gap ( ,.=2.13 eV) is substantially blue-shifted relative to PTV itself. Despite the low effective conjugation, the material is reasonably conductive when doped with l2 (cr=0.4 S cm 1). 

Farid and co-workers88 have investigated the effect of a glassy polymer host on the spectral position of the excimer emission peak produced by high concentrations of the compound methyl 4-(l-pyrenyl)-butyrate. The excimer peak position in a glassy polymer host was compared to the peak position in fluid solution for the following polymer hosts (and solvents) PS(toluene), PMMA(methyl isobutyrate), and poly-(vinyl benzoate) (methyl benzoate). The excimer emission peak of the pyrene compound in all three solvents occurred at about 20,800 cm-1, but the emission peak in all three polymer hosts was blue-shifted about 1900 cm-1 relative to the solution value. This is in contrast to the behavior of unsubstituted pyrene in PMMA 82) and PS 83), whose excimer peak does not shift from the solution value. 

The conjugation length of poly(3-alkylthiophene)s can be determined from the absorption maximum in the electronic spectrum. Whereas regioregular (i.e., head-tail) poy(3-octylthiophene) (POT) displays a maximum at 442 nm in CHCl3/Freon-113 solution, the absorbance maximum of 504 is blue shifted by 114 to 328 nm. This blue shift could arise from a particularly low molecular weight. 

The amorphous poly(541), poly(540), and poly(539) pristine films exhibited structureless absorption bands at 416, 423, and 438 nm, respectively, which are significantly blue shifted compared with the lowest vibrational band of P3HT ( 640 nm) (04MM6306 07AM833 08JA3030). On the other hand, the more crystalline poly(543), poly (542), poly(545), and poly(544) pristine films exhibited more structured, red-shifted absorption bands with a shoulder or a vibrational band corresponding to the lowest vibronic transition at 635, 612, 633, and 640 nm, respectively, which is more comparable to that of... 

Detailed information on the conformation and orientation of polysilane thin films has been obtained by anisotropic PL.80 The alignment of poly (methylphenylsilane-co-methacryloxypropyltriethoxysilane) [P(MPS-co-MPTES)] adsorbed on silica substrates has been studied at 14 K using an attenuated He-Cd polarized laser beam (X = 325 nm) as the excitation source. Laser irradiation decreases the PL intensity, blue shifts the PL peak position... 

Polysilane-based nanostructured composites were synthesized by the inclusion of poly(di-w-hexylsilane) (Mw = 53,600) into mesoporous, Si-OH-rich silica with a pore size of 2.8 nm.81 Two PL bands are observed for the composite. A narrow band at 371 nm, assigned to a PDHS film on a quartz substrate is blue shifted by 20 nm, a shift attributed to the polymer being incorporated into the pores.82 The size of the monomeric unit of the PDHS is about 1.6 nm, so only one polymer chain can be incorporated into a mesopore with a diameter of 2.8 nm. The narrow PL band at 350 nm is due to the reduction of the intermolecular interactions between polymer chains. This narrow PL band at 350 nm is assigned to the excited state of the linear polymer chain.81 Also, a new broad band of visible fluorescence at 410 nm appeared, which is assigned to localized states induced by conformational changes of the polymer chains caused by its interaction with the silanol (Si-OH) covered pore surface. Visible luminescence in nanosize PDHS is observed only when the polymer was incorporated in hexagonal pores of 2.8 nm and is not seen for the polymer incorporated into cubic pores of 2.8 nm diameter or hexagonal pores of 5.8 nm diameter. 

Sato and Woody found a preference for binding left-handed conformers of ANS to the beta form of poly(Lys) and suggested that the dyes are bound to the polypeptide in regions of low polarity due to the increase in fluorescence quantum yield and the blue shift in the emission spectrum [261],... 

Figure 3.56. UV spectra of an aliphatic poly silane demonstrating bleaching and blue shifting. Reproduced with permission from reference 192. Copyright 1984 Society of Photo-Optical Instrumentation Engineers.)...

The poly(dialkyl) stannanes, (Hex2Sn) and (Oct2Sn) exhibit a reversible thermochromic behavior upon warming above room temperature. The A. iax values of these polymers undergo a blue-shift from 384 to 369 nm for poly(di-n-octyl)stannane between 30 0 °C in toluene and from 392 to 382 nm in... 

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