Real-Time Mid-IR Monitoring of the Initiation and Propagation in Epoxi-Initiated Living Isobutylene Polymerizations

Abstract

The initiation and propagation of isobutylene (IB) polymerization initiated by 1,2-epoxi-2,4,4-trimethylpentane (TMPO-1)/TiCl 4 was monitored by a new fiber-optic transmission mid-IR probe. The real-time IR data provided insight into the initiation mechanism. Polyether formation, isomerization of the TMPO-1 into 2,4,4-trimethylpentanal, and its complexation by TiCl4 were observed, which occurred simultaneously with initiation of IB polymerization. The proposed initiating mechanism involves the formation of tertiary carbocations, which has been claimed to occur in the cationic polymerization of epoxides by the SN1 mechanism. On the basis of our results, the competitive occurrence of both SN1 and SN2 pathways is proposed. Interestingly, ketone/TiCl4 systems were found to initiate IB polymerization, albeit with very low efficiency. IR monitoring of these systems gave additional insight into the initiating mechanism. IB polymerization was monitored by following the disappearance of the second overtone of the C-H wag in the dCH2 group in IB at 1780 cm -1 and the CdC stretch at 1655 cm -1 . The linearity of first-order monomer consumption plots and the production of nearly uniform polyisobutylenes (PIBs) (Mw/Mn ) 1.06-1.13) indicated living conditions.

Macromolecular Engineering via Carbocationic Polymerization: Branched Structures, Block Copolymers and Nanostructures

“…For instance, MSE showed 40% I eff , while TMPO-1 had less than 1% I eff . In-situ FTIR monitoring gave further insight into the initiation step, [61] supporting the proposed initiating mechanism. Controlled initiation with external epoxides such as MSE would yield a primary hydroxyl head group and a tertchloride end group.…”

Primary Hydroxy-Terminated Polyisobutylene via End-Quenching with a Protected N-(ω-Hydroxyalkyl)pyrrole

“…For example, maximum initiation efficiencies of 40% where reported for R-methylstyrene epoxide, and apparently lower efficiencies were obtained for molecular weight targets under 4000 g/mol. 16 The low initiation efficiencies were caused by epoxide rearrangement (e.g., formation of aldehydes) and formation of polyethers, 17 the extent of such side reactions being determined by the initiator structure. 18 Knoll et al 19 demonstrated the in situ synthesis of allyl chloride-terminated PIB by charging 1,3-butadiene to BCl 3 -catalyzed isobutylene polymerizations.…”

Synthesis, characterization and biological activity of C60 derivative

“…The kinetic investigation on cationic polymerization of IB has been conducted by in situ FTIR 33–36. The strength of peak at 887 cm −1 reflects directly the concentration of IB in polymerization system 33–36.…”