Study of the direct detection of crosslinking in hydrocarbons by 13C‐NMR. II. Identification of crosslink in model compound and application to irradiated paraffins

A 13C‐NMR investigation was carried out in aid of direct detection of crosslinks in hydrocarbons with the future objective of studying radiation‐induced crosslinking in polyethylene by a direct method. The resonance signal due to a tertiary carbon atom appropriate to a crosslink far remote from molecular ends has been identified in a definitive manner with the aid of the H‐shaped model compound 1,1,2,2‐tetra(tridecyl)ethane synthetized in Part I of this study. This identification was then put to use in the examination of the irradiated linear paraffins n‐hexadecane and n‐eicosane, where it enabled the detection of radiation‐induced crosslinks. This crosslinking could then be associated with corresponding changes in molecular weight (dimer, trimer formation) as revealed by discrete peaks in the gel‐permeation chromatograms of the same samples and randomness of the crosslinking process in the liquid state of these compounds being inferred.