Quantum-chemical calculations of the IR absorption spectra of modified polytetrafluoroethylene forms

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DFT(B3LYP) (basis set 6–31 + G(d)) and HF (basis set 6–31G) calculations were performed to determine the geometric structure and vibrational spectra of the CnF2n and CnF2nO molecules (n = 3–13). The IR spectra of chain CnF2nO molecules with the terminal carbonyl group (-COF) were found to contain a band at 1885 cm−1. The C=C and C=O stretching vibrations of the-CF=CF2 and COF terminal groups were independent, and there was no mutual influence of their frequencies starting with the seven-fragment molecule. In the presence of chain branching, the sensitivity of the ν(C=C) and ν(C=O) frequencies in the olefin and carbonyl groups depended on where branching occurred. The chain configuration was found to be energetically favorable compared with branched structures.