Assessing
the Nanoscale Structure and Mechanical Properties
of Polymer Monoliths used for Chromatography
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Abstract
Concerning
polymeric monolithic materials utilized in separation
science, the structural and mechanical characteristics from the nanoscopic
to the macroscopic scale remain of great interest. Suitable analytical
tools are urgently required to understand the polymer monolith’s
constituent structure, particularly in the case of nanoscale polymer
properties that tend to develop gel porosity in contact with a mobile
phase ultimately affecting the chromatographic performance. Herein
described are our first findings from a characterization of commercially
available analytical polymer monoliths based on styrene/divinylbenzene
and methacrylate chemistries utilizing confocal Raman spectroscopy
imaging and atomic force microscopy (AFM). Confocal Raman spectroscopy
can be used to generate a three-dimensional representation of monoliths
in both dry state and in contact with solvent. AFM force–indentation
measurements on individual cross-sectioned globular features permit
detailed assessment of mechanical properties of the stationary phase.
This approach allowed so far unprecedented insight and identification
of a heterogeneous cross-link density distribution of polymer material
within individual globular features on a submicrometer scale