Naphthyl polymers

It was also found in the CPF spectra that no circular polarization was detected in the monomer fluorescence of poly(l- and 2-napAla)s. This indicates that the lowest-energy excited state of the naphthyl polymers is virtually localized on a monomeric naphthyl group and not delocalized over neighboring chromophores to form an exciton state. 

Even though the triplet appears localized, at least on a vibrational time scale, the apparent delayed fluorescence does indicate substantial mobility on the time scale of phosphorescence decay. We have examined these decays and found them to be quite nonlinear. With the exoeption pf the g-naphthyl polymer, the first half lives are about 1-2 x 10 seconds. 

The phosphorescence spectra of the two aryl polysilylenes studied are shown in Figure 9 and their fluorescence at room temperature in Figure 10. Although phosphorescence quantum yields for these two polymers were not measured, estimates based on comparison with the alkyl intensities indicate that these polymers emit with substantially greater yield. Todesco and Kamat (21 ) have measured the phosphorescence yield of a copolymer of a-naphthyl methyl and dimethyl silylene units to be 0.39. Our naphthyl polymer gives clearly the most intense phosphorescence and probably has a quantum yield near the 0.39 value for the copolymer. We estimate the phenyl polymer yield to be = 1/10 of the naphthyl polymer. 

We have examined the emission spectra of a variety of polysilylenes as thin films and solutions. The solution fluorescence ther-mochromism provides evidence to support the rotational isomeric state model used to interpret the absorption spectrum. The structured character and low yield of phosphorescence in the alkyl polysilylenes suggest that the triplet is the immediate precursor to photochemical scission. The change in character of both fluorescence and phosphorescence on progressing from phenyl to naphthyl in the aryl series indicates that the transitions in the naphthyl polymers are principally ir—it. ... 

Oxidation of LLDPE starts at temperatures above 150°C. This reaction produces hydroxyl and carboxyl groups in polymer molecules as well as low molecular weight compounds such as water, aldehydes, ketones, and alcohols. Oxidation reactions can occur during LLDPE pelletization and processing to protect molten resins from oxygen attack during these operations, antioxidants (radical inhibitors) must be used. These antioxidants (qv) are added to LLDPE resins in concentrations of 0.1—0.5 wt %, and maybe naphthyl amines or phenylenediamines, substituted phenols, quinones, and alkyl phosphites (4), although inhibitors based on hindered phenols are preferred. 

The beta-conidendrol is incorporated as an antioxidant and is frequently referred to in the patent literature, as is also di-P-naphthyl-p-phenylenediamine for this purpose. It is claimed that in the example given above the degradation rate at 222°C is only 0.09% per minute compared with typical values of 0.6-0.8% for unesterified polymer. 

For example, using hydroxy-terminated polybutadiene as the binder, RDX as the expl, toluenediisocyanate as a co-polymer, sym-di-(2-naphthyl)-p-phenylenediamine as an antioxidant, and poly butene as the plasticizer in a wt % ratio of 12.1/42.7/5/0.2/40, a castable expl is produced. 

As well as phenyl derivatives, other products have been prepared by hydrolysis of alkoxysilanes such as cyclohexenyl or naphthyl derivatives as well as heterocyclic compounds based on thienyl rings (Table 31, entries 28-33). Few practical applications have been reported for this type of compound, except for the styryl compound T81C6H4-A-CFI = CH2]s, and the fluorinated TslCeFsJs which have been used in polymer blending (Table 31, entries 13 and 28). ... 

Stabilisers are usually determined by a time-consuming extraction from the polymer, followed by an IR or UV spectrophotometric measurement on the extract. Most stabilisers are complex aromatic compounds which exhibit intense UV absorption and therefore should show luminescence in many cases. The fluorescence emission spectra of Irgafos 168 and its phosphate degradation product, recorded in hexane at an excitation wavelength of 270 nm, are not spectrally distinct. However, the fluorescence quantum yield of the phosphate greatly exceeds that of the phosphite and this difference may enable quantitation of the phosphate concentration [150]. The application of emission spectroscopy to additive analysis was illustrated for Nonox Cl (/V./V -di-/i-naphthyl-p-phcnylene-diamine) [149] with fluorescence ex/em peaks at 392/490 nm and phosphorescence ex/em at 382/516 nm. Parker and Barnes [151] have reported the use of fluorescence for the determination of V-phenyl-l-naphthylamine and N-phenyl-2-naphthylamine in extracted vulcanised rubber. While pine tar and other additives in the rubber seriously interfered with the absorption spectrophotometric method this was not the case with the fluoromet-ric method. 

In an acetone extract from a neoprene/SBR hose compound, Lattimer et al. [92] distinguished dioctylph-thalate (m/z 390), di(r-octyl)diphenylamine (m/z 393), 1,3,5-tris(3,5-di-f-butyl-4-hydroxybenzyl)-isocyanurate m/z 783), hydrocarbon oil and a paraffin wax (numerous molecular ions in the m/z range of 200-500) by means of FD-MS. Since cross-linked rubbers are insoluble, more complex extraction procedures must be carried out (Chapter 2). The method of Dinsmore and Smith [257], or a modification thereof, is normally used. Mass spectrometry (and other analytical techniques) is then used to characterise the various rubber fractions. The mass-spectral identification of numerous antioxidants (hindered phenols and aromatic amines, e.g. phenyl-/ -naphthyl-amine, 6-dodecyl-2,2,4-trimethyl-l,2-dihydroquinoline, butylated bisphenol-A, HPPD, poly-TMDQ, di-(t-octyl)diphenylamine) in rubber extracts by means of direct probe EI-MS with programmed heating, has been reported [252]. The main problem reported consisted of the numerous ions arising from hydrocarbon oil in the recipe. In older work, mass spectrometry has been used to qualitatively identify volatile AOs in sheet samples of SBR and rubber-type vulcanisates after extraction of the polymer with acetone [51,246]. 

The same group recently reported that the TBB defects can be brought below the nuclear magnetic resonance (NMR) detection limit by employing similar polymerization conditions (i-BuOK in THF at room temperature) in the synthesis of naphthyl-substituted PPVs 51-53 [112]. Although the absorption and PL spectra of all three polymers are similar, the EL can be finely tuned between 486 nm (for 52) and 542 nm (for 53). The external QE (studied for ITO/PEDOT/polymer/Ba/Al device) is also sensitive to the substituents pattern in the naphthyl pendant group 0.08% for 51, 0.02% for 52, and 0.54% for 53. 

N.H.S. Lee, Z.-K. Chen, W. Huang, Y.-S. Xu, and Y. Cao, Synthesis and characterization of naphthyl-substituted polyfp-phenylene vinylene)s with few structural defects for polymer light-emitting diodes, J. Polym. Sci., Part A Polym. Chem., 42 1647-1657, 2004. 

Soluble polymer-supported (i )-BINAP ligands were employed for the preparation of the Ru -bearing catalysts (54) and (55) which are shown in Scheme 4.33 [126]. Both these catalysts exhibited high activity and enantioselectivity in the asymmetric hydrogenation of 2-(6 -methoxy-2 -naphthyl)propenoic add. 

Usually, the PFR serves as a probe reaction for the study of the morphology of the matrix. This has been demonstrated by Weiss and co-workers in a series of recent articles on the photoreactivity of esters included in several polyethylene films. Low-density polyethylene (LDPE) films hosting 2-naphthyl esters bring about different selectivity in the PFR as compared with the reaction in solution. In addition, the selectivity is different if the polymer is stretched [286,287], Table 16 indicates the different product distributions upon irradiation of 2-naphthyl esters, depending on the nature of the solvent or matrix. The most striking fact is that irradiation of 2-naphthyl myristate leads to the coupling at the position 1 in ferr-butanol with 86% yield, whereas this product is absent in the irradiations in polyethylene films. Moreover, the product of coupling at position 3 is absent... 

Time-resolved fluorescence has been used for the study of the PFR on poly(methyl methacrylate). It has been found that the photoproducts of 2-naphthyl acetate in some zones of the material act as long-range quenchers for the unreacted esters in other zones of the polymer. A nonrandom chromophore distribution is generated in this way [293]. 

A similar but smaller intramolecular quenching effect was seen by Phillips and co-workers 44,4S) for 1-vinylnaphthalene copolymers incapable of excimer fluorescence. The monomer fluorescence lifetime of the 1-naphthyl group in the methyl methacrylate copolymer 44) was 20% less than the lifetime of 1-methylnaphthalene in the same solvent, tetrahydrofuran. However, no difference in lifetimes was observed between the 1-vinylnaphthalene/methyl acrylate copolymer 45) and 1-methylnaphthalene. To summarize, the nonradiative decay rate of excited singlet monomer in polymers, koM + k1M, may not be identical to that of a monochromophoric model compound, especially when the polymer contains quenching moieties and the solvent is fluid enough to allow rapid intramolecular quenching to occur. 

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