Characterization of the structure and crystalline polymorphism present in aliphatic polyketones by Raman spectroscopy

Raman spectroscopy has been used for the first time for the characterizatio n of perfectly 1:1 alternating a-olefin:carbon monoxide aliphatic polyketon es produced by the polymerization of ethene with carbon monoxide (ECO polym ers) and mixtures of ethene and propene with carbon monoxide (EPCO polymers ). A procedure to determine the methyl branch content arising from propene incorporation in EPCO polymers was established. This is based on the good c orrelation found between the intensity of a Raman band assigned to -CH3 ben ding and the propene incorporation determined by H-1 NMR spectroscopy. A me asure of the relative degree of crystallinity was made from the CO stretchi ng band, and this was correlated with the heat of fusion determined by diff erential scanning calorimetry. Band shapes in the range assigned to -CH2- b ending were attributed to factor group splitting effects (correlation split ting) and were interpreted to infer the presence of the two crystal forms ( alpha and beta) which have previously been identified by X-ray diffraction for aliphatic polyketones.