Ozge Guney-Altay, Chemical and Life Science Engineering Department, Virginia Commonwealth University, 601 W. Main St., Richmond, VA 23284-3028, Dmitry Pestov, Mechanical Engineering Department, VCU, 601 W. Main St., Richmond, VA 23284-3028, and Gary Tepper, Mechanical Engineering Department, Virginia Commonwealth University, 601 West Main Street, Room 318, Richmond, VA 23284-3015.
We report on submicron particles of a diethyl ester of p-phenylenediacrylic acid (EPA) whose molecular size selectivity can be tuned by an imprinting procedure applied during the solid-state photo-polymerization reaction. EPA monomer particles are produced by Rapid Expansion of Supercritical Solutions (RESS), and deposited directly on Surface Acoustic Wave (SAW) resonators. Dynamic sorption isotherms of C1- through C9-alkanes were studied to characterize the particulate coatings on SAW sensors. The mass changes due to vapor uptake resulting from the selective sorption into the particulate coatings can be measured accurately due to the high stability of the coatings and the nanogram sensitivity of the piezoelectric crystal. The selectivity and molecular porosity of the particulate coatings were studied in situ on the piezoelectric crystals by measuring sorption isotherms. Exclusion of progressively smaller molecules from the molecularly imprinted particulate coatings is observed as a function of the template molecule size. The observed reversible adsorption of alkane analytes with different molecular sizes and shapes suggest that these imprinted polymers may be categorized as organic analogs of zeolites.