Rahbar Amene, Falcone Bruno, Pareras Gerard, Nekoomanesh-Haghighi Mehdi, Bahri-Laleh Naeimeh, Poater Albert
Polymerization Engineering Department, Iran Polymer and Petrochemical Institute (IPPI), P.O. Box 14965/115, Tehran, Iran.
School of Chemistry, University College Cork, College Road, T12 K8AF, Cork, Ireland.
Chempluschem. 2023 Jan;88(1):e202200432. doi: 10.1002/cplu.202200432.
Continuing efforts aimed at performing the 1-decene polymerization to low viscosity polyalphaolefins (PAO)s using a less hazardous AlCl catalyst than boron-based analogs, the basic mechanisms of this system were revealed in this research. In this aspect, neat AlCl and AlCl /toluene were carried out to perform 1-decene polymerizations. Microstructure analyses of the as-synthesized oils revealed low molecular weight (708 vs. 1529 g/mol), kinematic viscosity (KV =6.4 vs. 22.2 cSt), and long chain branching (82.1 vs. 84.7) of PAO from the system containing toluene solvent. Furthermore, NMR analysis confirmed various types of short chain branch (SCB) with the inclusion of toluene ring in the structure of final PAO chains. Then, to shed light on the basic mechanisms of cationic polymerization of 1-decene including: i) chain initiation, ii) chain transfer to the monomer, iii) isomerization of the carbocation via a chain walking mechanism (causes different SCB length), and iv) binding of toluene ring to the propagating PAO chain (to yield aromatic containing oligomers), molecular modeling at the DFT level was employed. The energies obtained confirmed the ease of carbocation isomerization and chain transfer mechanisms in toluene medium, which well confirms the highly branched structure experimentally obtained for related PAO.
为了使用比硼基类似物危害更小的AlCl催化剂将1-癸烯聚合成低粘度聚α-烯烃（PAO），人们持续努力，本研究揭示了该体系的基本机理。在这方面，采用纯AlCl和AlCl/甲苯进行1-癸烯聚合反应。对合成油的微观结构分析表明，含甲苯溶剂体系中PAO的分子量较低（708对1529 g/mol）、运动粘度较低（KV = 6.4对22.2 cSt）且长链支化度较低（82.1对84.7）。此外，核磁共振分析证实了最终PAO链结构中包含甲苯环的各种短链支化（SCB）类型。然后，为了阐明1-癸烯阳离子聚合的基本机理，包括：i）链引发，ii）向单体的链转移，iii）通过链行走机理使碳正离子异构化（导致不同的SCB长度），以及iv）甲苯环与增长的PAO链结合（生成含芳族低聚物），采用了密度泛函理论（DFT）水平的分子建模。获得的能量证实了在甲苯介质中碳正离子异构化和链转移机理的容易程度，这很好地证实了相关PAO实验得到的高度支化结构。
