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

• Published in: International journal of polymer analysis & characterization Vol. 24; no. 6; pp. 556 - 570
• Main Authors: Sadjadi, Samaheh, Bahri-Laleh, Naeimeh, Nekoomanesh-Haghighi, Mehdi, Ziaee, Farshid, Dehghani, Sedva, Shirbakht, Sedigheh, Rahbar, Ameneh, Barough, Mehdi Salehi, Mirmohammadi, Seyed Amin
• Format: Journal Article
• Language: English
• Published: Taylor & Francis 18.08.2019
• Subjects: AlCl; Cationic; microstructure; oligomerization; PAO; α-olefin
• ISSN: 1023-666X; 1563-5341
• DOI: 10.1080/1023666X.2019.1627027

In this study, three middle range α-olefin monomers including 1-hexene, 1-octene, and 1-decene were oligomerized using conventional AlCl 3 /H 2 O catalytic system. Molecular weight and microstructure of the oligomers were analyzed by GPC and 1 HNMR, respectively. By 1 HNMR spectra, both internal (CHR=CHR′ and CHR=CR′R′′) and external (CH 2 =CR′R′′) olefins containing di and tri-substituted C=C bonds were detected. After successful oligomerization, synthesized polyα-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 1 HNMR spectroscopy. The microstructure of the synthesized oligomers was rationalized using the ratio under the peak of CH + CH 2 /CH 3 hydrogens (S1/S2) in 1 HNMR 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 1 HNMR and GPC analyses.