Abstract A phenyl-containing room temperature vulcanizeable (RTV) silicone raw material and polystyrene polymers can be separated on a phenyl-bonded phase LC column using both UV and fluorescence detections. The multimode LC behavior was observed for both the RTV silicone raw material and the polystyrene polymers. This means that the same chemically bonded phase can have different elution behaviors under different mobile phase environments. In pure tetrahydrofuran (THF) eluent, size exclusion behavior is observed for both samples. In THF/H2O gradient elution, polymers are retained and elute according to their solubility in the mobile phase.