Normal modes and their dispersion in poly(α-isobutyl-β-l-aspartate)

A study of vibrational dynamics of poly (a-n-butyl-b-l-aspartate) (panbla)

“…Although the spectrum is not available below 450 cm -1 , calculations are expected to be correct for more than one reason. First, they occur in the same range, as these modes in other systems do [11][12]. Second, since the force constants which are involved in low frequency region are also involved in the higher frequency region wherein they yield "good" frequencies, the results in this frequency region should also have a reasonably close predictive value.…”

“…The asymmetric, symmetric stretch, and scissoring modes of the methylene group of backbone (C β H 2 ) are calculated at 2899, 2859, and 1426 cm -1 respectively. The above modes lie in the same range in PAIBLA [11] and poly (4-methyl, 1-pentene) {P4MP1} [18]. These modes are highly localized and nondispersive in nature.…”

“…1) contains 25 atoms, which give rise to 75 dispersion curves. Initially the force constants were transferred from PAIBLA [11] (tetragonal form) and systems having similar environment and then refined to give the "best" fit to the FT-IR spectra (see Fig. 2).…”

“…It can be used to determine crystallinity, conformation, intra and intermolecular hydrogen bonding, fold structure of polymers, composition and sequence distribution in copolymers. Normal mode analysis has been performed for both tetragonal and hexagonal forms of PAIBLA to understand the dynamical behaviour [11][12]. However, no such work has been done for PANBLA.…”

“…We have compared the amide modes of PANBLA with other ω helical conformations such as PAIBLA [11], poly(N ε -p-bromobenzyl-L-ornithine) (PBrBO) [16], poly (L-phenylalanine) (PLPA) [17] as shown in Table 5. Some differences in lower range may be due to mixing of amide modes in this region.…”