Inverse gas chromatography of poly( n ‐butyl methacrylate): Effect of flow rate on specific retention volume and detection of glass transition temperature

Flow‐rate effect on specific retention volume ( V   g 0 ) was studied by eluting aliphatic, aromatic, and chlorinated aliphatic probes at infinite dilution on poly( n ‐butyl methacrylate) stationary phase at different temperatures from −10 to 150°C, encompassing both the glass transition ( T g ) and the softening temperatures of the polymer. The effect became pronounced as the temperature was reduced below 100°C. V   g 0decreased with an increase in the flow rate: first linearly at temperatures between 70 and 100°C, and then nonlinearly at all temperatures below 70°C. The retention diagrams of n ‐pentane, isooctane, and cyclohexane alone enabled the detection of glass transition. Dichloromethane gave a linear retention diagram through T g without showing the flow‐rate effect.