Raman Spectral Conformational Order Indicators in Perdeuterated Alkyl Chain Systems

Abstract

Conformational order indicators for perdeuterated alkyl chain systems are identified in the Raman spectra of nonadecane-d40, polyethylene-d4, and stearic acid-d35. Six spectral indicators are identified: I[nu(a)(CD2)2196]/I[nu(a)(CD2)2172], I[nu(C-C)G]/I[nu(C-C)T], I[nu(s)(CD3)]/I[nu(a)(CD2)2172], I[nu(s)(CD2)]/I[nu(a)(CD2)2172], and the full width at half-maximum (fwhm) and frequency of the nu(s)(CD2) mode. Among these indicators, the ratio of I[nu(a)(CD2)2196]/I[nu(a)(CD2)2172] is considered a primary indicator of conformational order, since it responds to alkyl chain conformational changes in a manner similar to the I[nu(a)(CH2)]/I[nu(s)(CH2)] primary indicator for hydrogenated systems. Other indicators are correlated to this primary indicator to derive a better understanding of the effect of structural attributes on conformational order in perdeuterated alkyl chain systems. These Raman spectral order indicators are applicable to any perdeuterated alkyl-containing system including lipids, biological membranes, alkylsilane-based chromatographic stationary phases, and self-assembled monolayers.

High‐Resolution Spectroscopic Mapping of the Chemical Contrast from Nanometer Domains in P3HT:PCBM Organic Blend Films for Solar‐Cell Applications

“…As has been pointed out before, since the thiophene rings in the P3HT molecules are more closely stacked when the polymer is highly crystalline, the increased crystallite size and better internal order within the P3HT domains obtained by annealing leads to the narrowing of the C¼C stretching Raman peak. [29] Our experiments clearly demonstrate that the presence of large PCBM aggregates deteriorates the regioregularity of the P3HT molecules. Similarly, P3HT C¼C Raman peak broadening effects have been reported by Yun et al [30] at 1 mm optical resolution comparing a series of P3HT:PCBM blend films that had been thermally annealed at different temperatures from 413 K to 300 K. We observed a similar effect and were able to clearly resolve the worsening of the P3HT local crystallinity at a spatial resolution of ca.…”

Raman spectroscopic identification of fullerene inclusions in polymer/fullerene blends

“…The peak position matches approximately with the literature value of 1469 cm −1 . [31,32] Two less intense peaks at 1425 and 1575 cm −1 arise from the Raman active modes H g (7) and H g (8) of the C 60 molecule.…”

“…Information about the nanomorphology has often been derived by indirect experimental methods such as absorption or Raman spectroscopy, which have been shown to be sensitive to changes in the local order or conformational properties 7–10. A direct measurement would require sufficient spatial resolution in the range of 20 nm or less, which is the typical domain size in P3HT/PCBM blends.…”

Raman spectra of deuterated hydrocarbons for labeling applications

“…The latter is an analog of the known all‐trans mode for hydrogenated hydrocarbon chains at 1130 cm −1 . [ 37 ] In some previous works, the identification of these two lines was confused, [ 26–29 ] but Snyder [ 23 ] and our numerical simulations of decane indicate this interpretation. Probably, difficulties with the identification of these modes were caused by the fact that the isotopic mass increase makes the vibrational modes being less characteristic (see atomic displacements for these modes in Figure S1).…”