Thermal degradation and theoretical interpretation of vibrational spectra of poly (beta,L-malic acid)

Abstract

Poly (β,l-malic acid) (PMLA) was obtained by Physarum polycephalum. The FT-IR and FT-Raman spectra were recorded experimentally and used for normal mode analysis using Wilson GF matrix method and phonon dispersion of PMLA. The non redundant set of internal coordinate are simplified. Urey-Bradley force field approximation was employed in normal mode analysis and to calculate the potential energy distribution (PED) of each fundamental vibration. Apart from detailed assignment, various characteristic features of dispersion curve have also been explained, arising due to internal symmetry in energy momentum space. Predictive values of the intramolecular contribution to the heat capacity of this polymer calculated by the density of states, are also been reported. The thermal degradation of PMLA was investigated in nitrogen atmosphere by thermogravimetric analysis in combination with DTA and FT-IR. The spectra of gases found in the thermal degradation of PMLA are very much similar to the spectra of gases released during decomposition of fumaric acid.