Polymers spectroscopic probing

It has seemed desirable to try to detect the postulated acylimidazole intermediate by spectroscopic probing. Acetylimidazole has been shown31 to have an absorbance maximum at 245 nm with an extinction coefficient of 3000. This absorbance should provide a basis for detection of the intermediate. However, in practice the strong absorbances due to the aromatic ester substrate (nitrophenyl caproate) and the product (nitro-phenol(ate)), added to the light scattering from the polymer, have made the spectrophotometric observation of the acylimidazole intermediate unfeasible under the reaction conditions previously described.26... 

It became of interest to see if we could obtain any indication of Schiff base formation with the polymer. Since spectroscopic probes would be obscured with the actual substrate, oxalacetate, because of the progress of the decarboxylation reaction (32), we have examined instead the spectra of oxalacetate-4-ethyl ester in solutions of the same modified poly-(ethylenimine) PEIQ—NH2. Such solutions develop a new absorption band at 290 nm. Furthermore, this band is essentially abolished if NaBH4 is added to the solution (Fig. 21). As is well known, NaBH4 reduces Schiff base linkages to amine groups.43-44... 

Luminescent Metal Complexes as Spectroscopic Probes of Monomer/Polymer Environments... 

Lees AJ (2001) Luminescent metal complexes as spectroscopic probes of monomer/polymer environments. In Ramamurthy V, Schanze KS (Eds) Optical Sensors and Switches. Molecular and Supramolecular Photochemistry Series, Vol 7, Chap 5. Marcel Dekker, New York, p 209... 

Constant-time imaging of H in solids has been applied in combination with MAS for line narrowing [Cor3, Cor4]. The images were recorded for a dynamically stressed poly(isoprene) phantom and of poly(butadiene) in two poly(butadiene)/poly(styrene) blends. Spectroscopic MAS imaging has also been tested on deuterated polymers to probe differences in molecular moblity from the lineshape of the rotary-echo envelope... 

Spectroscopic probes have been used to characterize the very weak solvent a/v and dipolarity of CO2, as reviewed elsewhere (1,32). Fourier transform IR spectroscopy (FTIR) has been used to show that CO2 interacts as an electron acceptor toward carbonyl groups in polymers, based upon splitting of the V2 bending mode of CO2 (33). Equilibrium constants have been... 

Caminati. G. Ottaviani, M.F. Gopidas, K. Jockusch. S. Turro. N.J. Tomalia, DA. Photochemical and spectroscopic probes of starburst dendrimers restricted spaces for photoinduced electron transfer and surfaces for the construction of supramolecular aggregates. Polym. Mater. Sci. Eng. 1995. 73. 80 - 81. 

The well-known polymer analyst Jack Koenig, in his widely-read book Spectroscopy of Polymers (1992) said "The majority of the spectroscopic techniques, such as UV and visible or mass spectroscopy, do not meet the specifications of the spectroscopic probe [for polymers].Koenig s rather skeptical opinion of mass spectrometry for polymer analysis was typical of the viewpoint of many scientists prior to the mid-1990s. 

Lees, A. J. Luminescent Metal Complexes as Spectroscopic Probes of Monomer/Polymer Environments. In Optical Sensors and Switches Ramamurthy, V., Schanze, K. S., Eds. Molecular and Supramolecular Photochemistry ries, Vol. 7 Marcel Dekker New York, 2001 Chap. 5, pp 209-255. 

In this chapter we present a description of the excited states of the phenyl-based light emitting polymers. This description is achieved by using the theoretical and computational modelling of these systems to interpret the experimental evidence acquired by a wide variety of spectroscopic probes. 

ESR has been useful in studying the influence of dissolved gases on polymer mobility [801]. Stable nitroxyl radicals, such as 2,2,6,6-tetramethylpipe-ridin-l-oxyl (TEMPO) are widely employed as spectroscopic probes for observing binding sites and molecular motion of macromolecules [802]. ESR spectra of the TEMPO free radical in PC film at various temperature and in solution were reported [795]. The TEMPO spin probe method was also used to study diisooctylphthalate (DIOP) plasticiser diffusion in suspension polymerised PVC particles [803]. Similarly, the compatibility Umit of PVAc and di-nonylphthalate (DNP) was studied by means of 2,2-di-n-nonyl-5,5-dimethyl-3-oxazolidinyloxy spin probe ESR measurements and DSC [804] DNP is an effective plasticiser for PVAc for concentrations not exceeding 17 wt.%. According to ESR evidence BBP in PVC forms radicals more easily than DOP [805]. 

The arsenal of electrochemical techniques that can be applied to the study of conducting polymer films on electrode surfaces is indeed broad and versatile, as the family tree in Fig. 20.4 indicates. The scope of these techniques is further enhanced when a spectroscopic probe is added as in the (thin-layer) spectroelectrochemical approach discussed later. We briefly examine each of these techniques in turn. With the amount of material involved here, it is not feasible to treat each topic in an exhaustive manner. Instead, only the underlying principles, typical experimental arrangements, and the type of information obtained in each instance are reviewed. The reader is referred to the literature cited for more extensive discussions. 

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