Gel permeation chromatography with crosslinked polystyrene gels and poor and theta solvents for polystyrene, 1. Universal calibration for cyclohexane at 35°C

Abstract

Abstract Gel permeation chromatography calibrations for polystyrene (PS) standards, poly(dimethylsiloxane), (PDS) fractions, and polyisoprene, (PI) samples have been obtained with a combination of four columns packed with crosslinked polystyrene gels using chloroform and cyclohexane as eluents at 35°C. Chloroform is a good solvent for all three polymers which separate according to steric exclusion, since they follow the same plot of log hydrodynamic volume vs. retention volume V R . Cyclohexane is a theta solvent for PS, but a good solvent for the other two polymers. PDS and PI in cyclohexane follow the same plot of log hydrodynamic volume vs. V R , but the plot for PS in cyclohexane is displaced to high V R values, the displacement increasing as V R increases. PS in cyclohexane gel permeation chromatograms are broader than the PS in chloroform chromatograms, the additional broadening increasing as the PS molecular weight decreases, i. e. as V R increases. Both the additional retention and broadening are explained by solute‐gel interactions, arising because PS prefers the polystyrene‐like gel environment rather than the mobile phase which is a theta solvent. The dependence of solute‐gel interactions, leading to partition and adsorption effects, on the polarity of the eluent is discussed.