An investigation of the production of low molecular weight polyisobutylene for the improvement of oil dispersants
The primary objective of this research was to develop a synthetic procedure for producing monodisperse, low molecular weight (LMW) telechelic polyisobutylene (PIB) in situ at elevated temperatures and in the absence of chlorinated hydrocarbons. Lubricant oils are comprised of several components including ashless dispersants, which consist primarily of PIBs carrying polar end groups such as imides and amines. Commercial production of PIB-based dispersants requires three separate steps: conventional polymerization of IB to form PIB-olefin, reaction of PIB-olefin with maleic anhydride to form PIB-succinic anhydride (PIBSA), and finally conversion of PIBSA to PIB-succinimides through reaction with polyamines. Synthesis of functionalized PIB through a single-step process could offer a considerable economic advantage over current production methods. A tremendous advantage of quasiliving polymerization is the opportunity for in situ functionalization of PIB by reaction of active chain ends with a desired reagent, such as a heteroatomic nucleophile. The current study specifically investigated the carbocationic polymerization of isobutylene (IB) at -10°C and evaluated the in situ quenching of various quasiliving systems with heteroatomic nucleophiles. In situ functionalization of quasiliving IB polymerizations with mildly nucleophilic reagents was investigated to develop a method for producing LMW, telechelic PIB in a single-step process. Polymerizations were conducted using the TMPCl/TiCl4 initiating system in Hex/MeCl at -70°C and the TMPCl/BCl3 initiating system in MeCl at -40°C, EtCl2 at -10°C, and Hex/2-NP at -10°C. 1 H NMR characterization was performed on quenched PIB aliquots to determine percent yield of quenched product. It was found that 1-methylpyrrole, 2-methylfuran, and 2-methylthiophene quantitatively yielded monoaddition products in TiCl4 catalyzed systems, and the trio quenched a moderate amount of PIB chain ends in BCl3 -catalyzed polymerizations conducted at -10°C. The study revealed that protic quenching agents and certain reagents containing a lone pair of electrons quantitatively produced tert -Cl chain ends in every system investigated. Quenching reactions conducted in Hex/2-NP solutions are the first reported and provide a method by which monodisperse, LMW telechelic PIB can be produced in the absence of chlorinated hydrocarbons.