Detailed characterisation of isomers present in polyalphaolefin dimer and the effect of isomeric distribution on bulk properties

This study has been conducted with the aim to gain detailed insight into the chemical nature of polyalphaolefin dimer (PAO dimer, C20H42). By using gas chromatography/mass spectrometry, a large number of isomers the complex mixture consists of has been identified; the variety of structural motifs ranges from a homologous series of almost linear vicinal dimethyloctadecanes to highly branched isomers such as 6,7‐dibutyldodecane. However, the mixture is characterised by the presence of isomers, which exhibit an intermediate degree of branching. Furthermore, a generally applicable protocol has been established to determine the relative content of these isomers. This protocol has then been applied to analyse samples from different PAO dimer batches, and a correlation between isomeric distribution and bulk properties, namely the viscosity–temperature behaviour, has been found. It turns out that the viscosity of PAO dimer depends less on temperature if the amount of weakly branched and almost linear isomers increases.