Poly vibrational analysis

P. R. Surjdn, M. Kertesz, Electronic structure and optical absorption of poly(biisothianaphthene-methine) and poly(isonaphthothiophene-thiophene) two low-bandgap polymers, J. Am. Chem. Soc., 113, 9865-9867 (1991) (j) J. KUrti, P. R. Suijan, Quinoid vs aromatic structure of polyisothianaphthene, J. Chem. Phys., 92, 3247-3248 (1990) (k) E. Faulques, W. WaUnbfer, H. Kuzmany, Vibrational analysis of heterocyclic polymers a com-... 

The refinement of an empirical force field for a macromolecule usually starts with the vibrational analysis of a smaller model system of known structure followed by a transfer of these force constants to the larger system, with possible subsequent force constant adjustments. In the case of the polypeptides, the preferred model system for the peptide group has been fra 5-N-methylacetamide (NMA), CH3CONHCH3. Synthetic polypeptides of known structure such as )9-sheet polyglycine (PG ), R = H, and a-helical and )8-sheet poly(L-alanine) (PLA), R = CH3, have served as basic examples of the polypeptide systems. 

The excellent agreement obtained for )5-PLA would indicate that this force field should be transferable to other APRS polypeptides, of course taking due accoimt of side-chain differences. This has been done for Ca-poly(L-glutamate), Ca-PLG [92], which X-ray and electron diffraction data had indicated to have an APPS structure but which were not extensive enough to provide a definitive conclusion. A proposed model [93] was used as the basis for the vibrational analysis, and the good prediction of the observed bands [92] supports both the model as well as the viability of the force field. The subtle differences between the -PLA and fi-Ca-PVG spectra are accounted for by the normal mode calculation, and emphasize the influence of the side chain on the main-chain modes, particularly on amide III. A similar successful vibrational analysis has been done on an alternating copolymer, APPS poly(L-alanylglycine) [19]. 

In a vibrational analysis of trans-l,4-poly(pentadiene), Neto et al. gave the dynamic equation of the vibrations of the single chain in terms of linear... 

The valence force fields for two secondary dichlorides has been developed as a preliminary to tackling the vibrational analysis of poly(vinylidene chloride). Some slight adjustments were made in the application to the polymer itself, where alternate bonds adopt non-ideal gauche angles. Symmetry arguments were required to supplement the frequency calculations for the purpose of conformational analysis. ... 

Lee S-H, Krimm S (1998) Ab initio-based vibrational analysis of a-poly(L-alanine). Biopolymers 46 283... 

S. Garreau, G. Louarn, S. Lefrant, J. R Buisson, and G. Froyer. 1999. Optical study and vibrational analysis of the poly(3,4-ethylenedioxyfhiophene) (PEDT). Synth Met 101(1-3) 312-313. 

MATSUURA H and miyazawa t, Vibrational analysis of molten poly(ethylene glycol) , / Polym Sci, 1969,7(A-2), 1735-1744... 

S.E. Barnes, E.C. Brown, M.G. Sibley, H.G.M. Edwards and P.D. Coates, Vibrational spectroscopic and ultrasound analysis for the in-process monitoring of poly(ethylene vinyl acetate) copolymer composition during melt extrusion, Analyst, 130, 286-292 (2005). 

Infrared and Raman spectra are useful, of course, in determining the symmetry of poly(nitrile) complexes. An example is dichlorobis(benzonitrile)platinum, a versatile starting material in platinum chemistry. There is a dispute in the literature as to whether it has a cis or trans configuration. (There is a general agreement that the corresponding Pd complex is trans.) It has recently been shown by X-ray structure analysis that both cis and trans complexes exist, and their vibrational spectra have been discussed.21... 

The most-used silicone lubricants in the fibre finishing applications are polydimethylsiloxane, polymethylphenylsiloxane, oleophilic silicone/organic copolymer (Fig. 5.7a), and poly(glycol silicone copolymer) (Fig. 5.7b). The analysis of silicones can be conducted by FTIR. A strong and often broad absorption in the 1000-1100 cm region can be attributed to the Si-O vibration. A peak at 1100 cm shows the Si-O-Si vibration. A sharp peak at 1260 cm" indicates the Si-( II. stretching absorption.- ... 

There are few methods suitable for on-line chemical analysis of aerosol particles. Raman spectroscopy offers the possibility of identifying the chemical species in aerosol particles because the spectrum is specific to the molecular. structure of the material, especially to the vibrational and rotational modes of the molecules. Raman spectra have been obtained for individual micron-sized particles placed on surfaces, levitated optically or by an eiectrodynamic balance, or by monodisperse aerosols suspended in a flowing gas. A few measurements have also been made for chemically mixed and poly disperse aerosols. The Raman spectrum of a spherical particle differs from that of the bulk material because of morphology-dependent resonances that re.su It when the Raman scattered photons undergo Mie scattering in the particle. Methods have been developed for calculating the modified spectra (McNulty el al., 1980). 

The guided tour, presented here, for the stepwise analysis of the vibrational data recorded for trans-PA, can be and has been, equally applied for the interpretation of the spectra and the structural analysis of other poly conjugated polymers such as polyparaphenylene [44], polypyrrole [45], poly thiophene [46] and their alkyl derivatives [47]. For these substances, more experimental data are needed. Moreover, additional theoretical problems must be considered, due to the fact that the electron delocalisation depends on the torsional angle between the aromatic rings. Moreover, these systems cannot sustain solitonic excitation, but only polarons or bipolarons can be formed with the generation of "quinoid structures."... 

In the infrared spectra of ethylene-vinyl acetate copolymer films, the ratio of the absorbances of the vinyl acetate C-O stretching vibration at 1020 cm and the ethylene CH2 rocking vibration at 720 cm may be employed as a measure of the composition. Infrared analysis of a number of ethylene-vinyl acetate copolymers of known composition produced the results listed in Table 6.3. The infrared spectrum of a sample of poly(ethylene-co-vinyl acetate) of unknown composition... 

---