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Ethylene Polymerizations Using Parallel Pressure Reactors and a Kinetic Analysis of Chain Transfer Polymerization
Published on: November 27, 2015
Gas-phase complexes of cyclic and linear polyethers with alkali cations
Paola Hurtado1, Ana R Hortal, Francisco Gámez
1Departamento de Sistemas Físicos, Químicos y Naturales, Universidad Pablo de Olavide, 41013 Seville, Spain.
Physical Chemistry Chemical Physics : PCCP
|September 17, 2010
Summary
Polymer backbone flexibility impacts molecular recognition. This study reveals distinct gas-phase structures of cyclic 15-crown-5 ether and linear polyethylene glycol chains complexed with alkali metal cations, highlighting differences in cation coordination.
Area of Science:
- Polymer Chemistry
- Supramolecular Chemistry
- Spectroscopy
Background:
- Polymer backbone flexibility is crucial for molecular recognition.
- Understanding how polymers interact with cations informs material science and drug delivery.
- Cyclic and linear polyethers exhibit unique structural properties.
Purpose of the Study:
- To characterize the gas-phase structures of complexes formed by cyclic and linear polyethers with alkali metal cations.
- To investigate the influence of polymer structure (cyclic vs. linear) on cation binding.
- To elucidate the coordination modes and structural motifs in these complexes.
Main Methods:
- Infrared multiple photon dissociation (IRMPD) spectroscopy to probe vibrational modes (800-1500 cm⁻¹).
- Density Functional Theory (DFT) calculations to complement experimental data.
- Analysis of gas-phase complexes of 15-crown-5 ether (15c5), polyethylene glycol 4 (PEG4), and polyethylene glycol 9 (PEG9) with K⁺, Rb⁺, and Cs⁺.
Main Results:
- 15-crown-5 ether complexes (15c5-M⁺) show distorted, asymmetric structures with cations above the ring and four coordinating oxygens.
- The linear PEG4-K⁺ complex adopts an inclusion-like five-coordinate structure with quasi-planar oxygens.
- The longer linear PEG9-K⁺ complex forms stable cages with eight coordinating oxygens, stabilized by terminal hydrogen bonds.
Conclusions:
- Polymer structure significantly dictates cation binding geometry and coordination number.
- Gas-phase studies provide fundamental insights into polyether-cation interactions.
- Flexibility and chain length influence the formation of distinct structural complexes, impacting molecular recognition.
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