Impact of dimensionality and confinement on reaction dynamics and thermodynamics within 1D and 2D nanostructures

Confinement has been shown to contribute to the dynamics of small molecules within nanoscale hydrophobic or hydrophilic cavities. Enclosure within a confined space can also influence energy transfer pathways, such as the enhancement of fluorescence over thermal relaxation. In this paper, the effect...

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Bibliographic Details
Published in:The Journal of chemical physics 2021-05, Vol.154 (17), p.174903-174903
Main Authors: McTaggart, Matt, Li, Xia, Groves, Michael, Shah, Vishva, Jugroot, Manish, Malardier-Jugroot, Cecile
Format: Article
Language:English
Subjects:
Bulk density
Bulk polymerization
Confined spaces
Confinement
Elastic scattering
Energy transfer
Fluorescence
Holes
Hydrophobicity
Kinetics
Neutron scattering
Packing density
Physics
Polymerization
Reaction kinetics
Solubilization
Thermal relaxation
Thermodynamic properties
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Summary:Confinement has been shown to contribute to the dynamics of small molecules within nanoscale hydrophobic or hydrophilic cavities. Enclosure within a confined space can also influence energy transfer pathways, such as the enhancement of fluorescence over thermal relaxation. In this paper, the effect of confinement on the thermodynamic properties and reaction kinetics of small hydrophobic molecules confined in a soft polymeric template is detailed. A quasi-elastic neutron scattering experiment identified a substantial decrease in translational diffusion of pyrrole after solubilization within a hydrophobic cavity. This decrease in mobility is due to pyrrole’s closer packing and increased density under confinement vs the bulk liquid. The decreased mobility and increased density explain the spontaneous polymerization reaction of pyrrole observed within the cavity. The precise characterization of the polymerization kinetics under confinement found that the reaction is independent of pyrrole concentration, consistent with the close packing density. Kinetic data also show that confinement dimensionality finds a thermodynamic expression in the transition state entropy. The dynamics and kinetics experiments reported here offer rare empirical insight into the important influence that cavity geometry places on the reactions they host.
ISSN:0021-9606
1089-7690
DOI:10.1063/5.0046081