Dependence of CC stretching wavenumber on polyene length in degraded polyvinyl chloride: a comparative empirical, classical mechanics, and DFT study

•Analytical model describing the polyene length dependence of CC stretch wavenumber.•Analytical polyene length determination tool for polyene monitoring in degraded PVC.•Polyene length determination tool with potential for elasticity constant correction.•Comparison of DFT and earlier empirical methods for polyene length determination.•Independent validity-test of empirical tools on the basis of a new analytical tool.