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

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 VR. 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. VR, but the plot for PS in cyclohexane is displaced to high VR values, the displacement increasing as VR 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 VR 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.