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Direct Chain End Functionalization of Living Polyisobutylene Using Phenoxyalkyl (Meth)acrylates
Conor P Roche1, Mark R Brei1, Bin Yang1
1The University of Southern Mississippi School of Polymers and High Performance Materials, 118 College Dr. # 5050, Hattiesburg, Mississippi 39406, United States.
ACS Macro Letters
|May 25, 2022
Summary
Phenoxyalkyl (meth)acrylates efficiently cap living polyisobutylene chains, with longer tethers (4-8 carbons) ensuring quantitative functionalization. Shorter tethers (2-3 carbons) show incomplete quenching due to carbocation rearrangement.
Area of Science:
- Polymer Chemistry
- Organic Synthesis
- Materials Science
Background:
- Living carbocationic polymerization offers precise control over polymer architecture.
- Effective chain-end functionalization is crucial for tailoring polymer properties.
- Developing efficient quenching agents for polyisobutylene (PIB) remains an active research area.
Purpose of the Study:
- To investigate phenoxyalkyl acrylates and methacrylates as quenching agents for living carbocationic polymerization of isobutylene (IB).
- To determine the effect of tether length on quenching efficiency and polymer end-group fidelity.
- To optimize quenching conditions for quantitative functionalization of PIB.
Main Methods:
- Synthesis of phenoxyalkyl (meth)acrylates via reaction of (meth)acryloyl chloride with phenoxyalkanols.
- Quenching of living IB polymerization using TiCl4 catalyst at -70 °C in hexane/methyl chloride.
- Characterization of quenched polymers using 1H and 13C NMR, MALDI-TOF mass spectrometry, and size exclusion chromatography (SEC).
Main Results:
- Alkylation occurred exclusively at the para position of the phenoxy moiety.
- Polymers quenched with longer tethers (4, 6, or 8 carbons) exhibited quantitative (meth)acrylate chain-end functionality (≥1.98).
- Shorter tethers (2-3 carbons) resulted in incomplete quenching due to carbocation rearrangement.
Conclusions:
- Phenoxyalkyl (meth)acrylates are effective quenching agents for living carbocationic polymerization of IB.
- Optimal quenching efficiency and quantitative functionalization are achieved with tether lengths of four or more carbons.
- Careful control of quencher to Lewis acid ratio is necessary to maximize quenching rate and prevent side reactions.
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