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Normal modes and their dispersion have been obtained for polyselenophene (PSe) in the reduced zone scheme using Wilson's GF matrix method as modified by Higg's for an infinite polymeric chain. The Urey Bradley potential field is obtained by least square fitting to the observed infrared and Raman bands. The results thus obtained agree well with the experimental IR and Raman values. The characteristic features of dispersion curves such as repulsion and exchange of character, crossing, van Hove type singularities have been discussed and possible explanation has been given. Heat capacity has been calculated via density-of-states using Debye relation in the temperature range 0–450 K. Possible explanation for the inflexion region in the heat capacity variation is given. The spectra of the oligomers are checked with the finite–infinite spectral relationship and are found to be in agreement.

Polyvinylidene fluoride (PVDF) is a polymer of industrial importance, mainly due to its piezoelectric and pyroelectric properties. A comprehensive study of the normal modes and their dispersion in PVDF (β-form) has been reported in the reduced zone scheme using Wilson’s GF matrix method as modified by Higgs. A Urey-Bradley force field has been used. The evaluation of normal modes and their dispersion has been taken to logical conclusion by calculating the heat capacity as a function of temperature. The extent of agreement with the experimental data supports the potential field. Characteristic features of the dispersion curves such as repulsion and exchange of character have also been discussed.

Normal modes and their dispersion are obtained for planar zig-zag form of poly(β-hydroxybutyrate) using Urey–Bradley force field. A comparison is made with the spectra of its helical form. Apart from detailed assignment of modes, various characteristic features of dispersion curves have been explained as arising due to internal symmetry in energy momentum space. The density-of-states have been used to calculate heat capacity in the temperature range 10–450 K using Debye's formalism.

Normal modes and their dispersion have been obtained for polychloroprene in the trans form using Wilson's G F matrix method as modified by Higg's for an infinite polymeric chain. Urey Bradley force field has been used. Several new assignments, which are missing in earlier work, are reported. The assignments of lower frequency modes have been confirmed using inelastic neutron scattering data. The characteristic features of dispersion curves have been explained. Variation of heat capacity as a function of temperature has been predicted. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Normal modes and their dispersion have been obtained for trans polydichlorobutadiene (PDCB) in the reduced zone scheme using Wilson’s G F matrix method as modified by Higg’s for an infinite polymeric chain. The Urey Bradley potential field is obtained by least square fitting of the observed infrared and Raman bands. The obtained results agree well with the experimental values. Because of the presence of centre of symmetry, the PDCB molecule obeys the mutual exclusion principle. Several new assignments which are missing in the earlier work are reported. The characteristic features of dispersion curves such as repulsion and exchange of character have been discussed and possible explanation has been given. Heat capacity has been calculated via density-of-states using Debye relation in the temperature range 10–450 K.

The normal modes and their dispersions for poly(l-asparagine) (PLN) in the α-helical form have been obtained in a reduced zone scheme with Wilson's GF matrix method as modified by Higgs. The results indicate that the modes below 1350 cm−1 show appreciable dispersion. Optically active frequencies corresponding to the zone center and zone boundary are identified and discussed. Some of the characteristic features of the dispersion curves are repulsion accompanied by an exchange of character and von Hove singularities. Amide modes, side chain modes, and mixed modes are reported. The heat capacity calculated from the dispersion curves via density-of-states using Debye's relation is compared with the experimental data in the temperature range of 220–390 K.

Microbial poly(e-L-lysine)(M-e-PL) is a naturally occurring biomaterial, which is water soluble, biodegradable, edible and non-toxic towards humans and environment. Normal mode analysis including phonon dispersion has been performed to understand completely the vibrational spectra of this polymer. Various characteristic features of the dispersion curves have been reported. The heat capacity is calculated as a function of temperature via density-of-states in the range 1-450 K.

Normal modes and their dispersion are reported for polydichlorophosphazene (PDCP). This polymer has several interesting features. Its backbone flexibility allows more than one structural possibility such as distorted cis‐trans planar, cis‐trans planar. PDCP can be used to prepare different polyphosphazenes which have many applications such as fire resistant materials, photonic materials, membranes, etc. Some of the distinguishing features of dispersion curves such as cross‐over, bunching and Von Hove type of singularities are discussed and possible explanations are given in terms of symmetry considerations. Several new assignments, which are missing in earlier work, are reported.

The normal modes and their dispersions for poly(L-tryptophan) (PLTR) in the α-helical form have been obtained in a reduced zone scheme with Wilson's GF matrix method as modified by Higgs. Dynamic studies of the α form are of special significance as it is the predominant secondary structure for protein molecules. X-ray and circular dichroism (CD) studies by Peggion et al. have confirmed the α-helical conformation of PLTR. The side group of PLTR is more complicated than that of other natural polypeptides. It consists of both a pyrrole and a benzene ring along with a CH2 group. Optically active frequencies corresponding to the zone center and zone boundary are identified and discussed. Some of the characteristic features of the dispersion curves are repulsion accompanied by an exchange of character and von Hove singularities. The heat capacity has been calculated via densities of state with Debye's equation in the temperature range of 220–390 K and has been compared with experimental measurements. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 316–332, 2004

The normal modes and their dispersions for poly(l-ornithine) in the unusual cross-β form have been obtained in the reduced zone scheme using Wilson's GF matrix method as modified by Higgs. Optically active frequencies corresponding to the zone center and zone boundary are identified and discussed. Some of the characteristic features of the dispersion curves are repulsion accompanied by an exchange of character and von Hove type singularities. Heat capacity has been calculated via density-of-states using Debye's equation in the temperature range 50–500K.

Poly(β-benzyl- l -aspartate) (PBLA) shows unusual conformational variety and under varying conditions of preparation it is capable of adopting four different conformations, namely left-handed α helix (αl), right-handed α helix (αr), ω helix and β pleated sheet. We present here a complete phonon dispersion and heat capacity study on the β form of PBLA. A comparison of the characteristic features and the conformational dependence of modes for α, β and ω forms of PBLA are made. It is observed that the dispersion of modes in the β form is in general larger than in the α form. Crossing over and repulsion of various dispersion branches are discussed.

The normal modes and their dispersion are obtained for syndiotactic poly(4-methyl-1-pentene) in the reduced zone scheme using Wilson’s GF matrix method as modified by Higgs. Urey–Bradley force field has been used. A comparison is made with the spectra of its isotactic form to identify conformational sensitive modes and other spectral differences. Heat capacity has been calculated via density-of-states using Debye relation in the temperature range 50–330 K and compared with the experimental measurements.

The normal modes and their dispersions for form 1 of syndiotactic poly(1-butene) have been obtained using Wilson’s GF matrix method as modified by Higgs. Optically active frequencies corresponding to the zone center and zone boundary are identified and discussed. The Urey Bradley potential field is obtained by least square fitting of the observed Fourier transform infrared absorption bands. Specific heat has been obtained from dispersion curves via density of states. A comparative study of isotactic and syndiotactic forms of poly(1-butene) is presented.

Phonon dispersion studies have been made on the cis-transoid form of polyacetylene (PA) chain. Unlike the trans-transoid form reported earlier, this conformation shows crossover and repulsion characteristics in the optical modes. Detailed assignments of modes are given, and the predictive value of the heat capacity obtained via the density of states as a function of temperature is reported.

Poly( O -acetyl, l -serine), which is a precursor of poly( l -serine) in synthesic sequence, is found to exist in cross-β conformation. Normal mode analyses including phonon dispersion have been performed, to understand completely the FTIR spectra of this polypeptide, using Wilson's GF matrix method and Urey–Bradley force field. The characteristic features of dispersion curves like repulsion, exchange of character and bunching have been observed and discussed. In addition to the above the heat capacity is calculated as a function of temperature via density-of-states derived from dispersion curves.

Polymers of 2-methyl-1,3-pentadiene are capable of existing in both isotactic, as well as syndiotactic, configuration. The isotactic 1,4-cis polymer also exists in two stable forms that have different melting points. A complete study of normal modes and their dispersion was carried out using Higgs modification of Wilson's dynamical GF matrix method and the Urey Bradley force field. The force constants have been best fitted to the Fourier transform infrared (FTIR) frequencies. Characteristic features of dispersion curves, like bunching, repulsion, and exchange of character between various pairs of modes, were observed and are discussed here. In addition, the frequency distribution function derived from dispersion curves was used to calculate the heat capacity in the temperature range 50–450 K.

Poly(S-benzyl-L-cysteine) (PBLC) is a S-benzyl derivative of the natural amino acid poly(L-cysteine). Its normal modes and their dispersion in antiparallel β-sheet conformation have been obtained within the first Brillouin zone using Wilson's G.F. matrix method, as modified by Higgs for an infinite polymeric chain. The zone center frequencies and the Urey Bradley force field have been obtained by best fitting the observed Fourier transform IR (FTIR) absorption bands. The characteristic features of dispersion curves such as crossing, repulsion, and exchange of character are discussed. Predictive values of heat capacity in the temperature range of 50-500 K are reported.

Calculations of normal modes of isotactic 1,4- trans -poly(1,3-pentadiene) and their dispersion within the first Brillouin zone (reduced zone scheme) are reported here. Calculated vibrational frequencies are compared with the reported IR spectroscopic data and a close agreement is found between the two. Characteristic features of dispersion curves, like bunching and repulsion, are observed and discussed. Frequency distribution function derived from dispersion curves is used to calculate the heat capacity in the temperature range 50–450 K.

The Zimm and Bragg theory for helix-to-coil transitions has been suitably amended and applied to explain the two-step transition in the DNA triplex. The experimental measurements reported elsewhere have been successfully interpre- ted. The order-order and order-disorder transitions associated with the melting of the DNA triple helix, with and without netropsin binding, were characterized by the nucleation parameter, enthalpy change, sharpness of transition, and heat capacity. The destabilization of the triplex and stabilization of the duplex on netropsin binding are reflected in these characteristic parameters.

Normal modes and their dispersion are reported for the α-helical form of poly( l -aspartic acid) which is an important polypeptide used in the sustained release of drugs. Characteristic features of dispersion curves such as bunching and repulsion are discussed. Heat capacity is derived from the dispersion curves via density-of-states and compared with the available experimental data on sodium salt of the polymer.

Phonon dispersion studies for trans-l,4-polybutadiene (TPBD) are reported. The change in profile of the dispersion curves as a function of the ═CH─CH2─ dihedral angle φ has been obtained in order to find the geometry of the polymer that gives the best interpretation of the spectra. It is found for φ = 71°. The regions of high density of states obtained from the dispersion curves for an isolated chain have been used to explain the features of the spectra. Some of these, which were earlier attributed to interchain interactions, in fact arise due to intrachain interactions. Prominent features of the dispersion curves are discussed and heat capacity, derived therefrom, is reported. Calculations have also been performed for unsaturated C-deuterated and fully deuterated TPBD samples to check the validity of the force field and assignments.

Normal modes and their full dispersions are obtained for the right-handed α-helical poly(l-tyrosine). Optically active modes corresponding to the zone center and at the helical angle are assigned. Both the assignments and the force field are supported by the spectra of N-D species. In addition, modes corresponding to the regions of high density of states and other characteristic features of dispersion curves such as repulsion and exchange of character are discussed. Conformation sensitive modes of other α-helices are compared. Heat capacity is obtained from the dispersion curves via density of states and it is found in agreement with the measured data.

In continuation to our work on the oligomapping of the dispersion curves of poly(L-valine) in β form, the present work is a study of normal modes and their dispersion in the α form. The Urey Bradley force field used in Wilson's GF matrix method has been transferred from the β form and refitted to explain the FTIR spectra. The characteristic features of the dispersion curves involve repulsion with character exchange and tendency of certain pair of modes involving the motion of C α atom to come closer near the helix angle. Predictive value of heat capacity is obtained from the density-of-states. It is observed that the mixed modes make the maximum contribution.

SYNOPSIS Poly(P-benzyl-L-aspartate) (PBLA) is an unusual polypeptide, which is capable of going into four different conformations, namely, left-handed a helix, right-handed a helix, o helix, and fi pleated sheet. The present work is a complete study of normal modes and their dispersion in the unusual left-handed a form. A special feature of some of the dispersion curves is their tendency to bunch in the neighborhood of helix angle. This is attributed to the presence of strong intramolecular interactions. Crossing and repulsion between the dispersion curves is also observed. The N-deuterated analogue of PBLA has been studied to check the validity of assignments and force field (Urey Bradley). Specific heat has been obtained from dispersion curves via density of states. A comparative study of left-handed and right-handed forms is presented. 0 1996 John Wiley & Sons, Inc.

The normal modes and their dispersions for isotactic poly(4-methyl-1-pentene) have been obtained in the reduced zone scheme using Wilson's GF matrix method as modified by Higgs. The zone centre frequencies and Urey—Bradley potential field have been obtained by fitting the observed Fourier transform infra-red absorption bands. Some of the characteristic features of the dispersion curves are repulsion, exchange of character and Von Hove type singularities. The heat capacity obtained from the density-of-states agrees with the experimental data up to 305 K, at which glass transition sets in and the experimental curve exhibits a marked change in slope.