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Efficient Synthesis of Polyfunctionalized Benzenes in Water via Persulfate-promoted Benzannulation of α,β-Unsaturated Compounds and Alkynes
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α-Substituent Effect on o-Vinylbenzaldehyde Cyclopolymerization
Bora Inci1, Pin-Nan Cheng1, Kyle Beljanski1
1Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, United States.
ACS Macro Letters
|May 24, 2022
Summary
Cationic cyclopolymerization of o-vinylbenzaldehydes using boron trifluoride shows temperature-dependent conversion. Low temperatures (-78 °C) enable complete polymerization of specific monomers, yielding thermally stable polymers.
Area of Science:
- Polymer Chemistry
- Organic Synthesis
- Materials Science
Background:
- Cationic polymerization is a key method for synthesizing polymers.
- o-Vinylbenzaldehydes are monomers with potential for unique polymer structures.
- Controlling polymerization conditions is crucial for achieving desired polymer properties.
Purpose of the Study:
- To investigate the cationic cyclopolymerization of o-vinylbenzaldehydes.
- To explore the effect of monomer structure and reaction temperature on polymerization outcomes.
- To characterize the properties of the resulting polymers.
Main Methods:
- Cationic cyclopolymerization using boron trifluoride as initiator.
- Varying reaction temperatures (-78 °C and 0 °C).
- Characterization of monomer conversion and polymer properties (thermal stability, glass transition temperature, mechanical properties).
Main Results:
- Incomplete conversion of o-vinylbenzaldehyde at 0 °C.
- Complete cyclopolymerization of alpha-methyl-substituted monomers at -78 °C.
- Formation of indenyl alcohol from alpha-phenyl-substituted monomer under polymerization conditions.
- Poly(o-(alpha-methyl)vinylbenzaldehyde) exhibits high thermal stability (T_onset = 340 °C) and a glass transition temperature (T_g) of 153 °C.
- The polymer is a brittle, glassy plastic with a storage modulus of 3 × 10^8 Pa.
Conclusions:
- Reaction temperature significantly impacts the cationic cyclopolymerization of o-vinylbenzaldehydes.
- Low temperatures are essential for complete polymerization of specific substituted monomers.
- The resulting poly(o-(alpha-methyl)vinylbenzaldehyde) possesses good thermal stability but brittle mechanical properties.
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