Azulene-Modified Polysiloxanes as Gas Chromatographic Stationary Phases: Comparison of the Separatory Properties of Azulene and Naphthalene

ABSTRACT

Azulene is an aromatic molecule with interesting properties, most notably a permanent dipole moment of 1.08D. This degree of polarity in the absence of heteroatoms is quite rare and offers potential for use in unique gas chromatographic stationary phases. Here, we report the first examples of azulene-derivatized stationary phases for gas chromatographic separations. Poly(dimethyl/azulenylmethyl) siloxane polymers containing 15 and 35% of an azulene derivative were synthesized, coated on capillary columns, and evaluated. To compare the effects of increased polarity vs. the effects of polarizability, isomeric naphthalene analogues were also prepared, coated, and evaluated. The coated phases displayed efficiencies up to 2700 plates/m. For both azulene and naphthalene columns, retention increased as substitution level increased. The more polarizable naphthalene columns tended to retain analytes more strongly. Columns were also evaluated for the separation of several different mixtures of isomers against a commercial HP-5 column. All azulene and naphthalene columns exhibited separations comparable to the commercial column. The solvation thermodynamic parameters phases were measured, showing an excellent linear relationship and no change in the mechanism of interaction over the temperature range measured.

KEYWORDS:

• Azulene
• gas chromatography
• stationary phase

Acknowledgment

The authors would like to thank Lilian Frink of the Armstrong group at UT Arlington for helpful discussions.