Rationalizing chain microstructure in the polyα-olefins synthesized by cationic AlCl3/H2O catalytic system

In this study, three middle range alpha-olefin monomers including 1-hexene, 1-octene, and 1-decene were oligomerized using conventional AlCl3/H2O catalytic system. Molecular weight and microstructure of the oligomers were analyzed by GPC and (HNMR)-H-1, respectively. By (HNMR)-H-1 spectra, both internal (CHR=CHR ' and CHR=CR ' R '') and external (CH2=CR ' R '') olefins containing di and tri-substituted C=C bonds were detected. After successful oligomerization, synthesized poly alpha-olefins underwent hydrogenation process using Pd(0)-Hal catalyst to yield synthetic oils of PHex, POct, and PDec, respectively and then completion of the hydrogenation was confirmed by (HNMR)-H-1 spectroscopy. The microstructure of the synthesized oligomers was rationalized using the ratio under the peak of CH+CH2/CH3 hydrogens (S1/S2) in (HNMR)-H-1 spectra and the degree of oligomerization obtained from M-n. According to the results, the best match between theoretical and real S1/S2 is obtained when considering double bond isomerization in the synthesized PAOs. By knowing PAO molecular weight, a relationship between monomer type and S1/S2 in the PAO homopolymers was detected. Our suggested methodology can be generalized to the unknown PAO homopolymers to unravel their monomer type by simple (HNMR)-H-1 and GPC analyses.