Monofunctional polymers in liquid adsorption chromatography: determination of the interaction parameter in the range of weak interaction

The main physical characteristics of monofunctionals in adsorption chromatography - the adsorption interaction parameter of the repeat units c and the interaction parameter of specific end group q - are discussed. Both parameters are independent on column dimensions and pore diameter, and depend on mobile phase composition. In a plot of elution volumes V(n) vs. the difference DeltaV=V(n)-V(n-1) in elution volumes of consecutive non-functional or monofunctional oligomers, straight lines with the same slope are obtained for sufficiently high molar masses. The intercept of these lines yield the accessible volumes of functionalized and non-functionalized oligomers. In the range of weak interaction, the interaction parameter of the repeat unit can be determined using monofunctional chains with strongly adsorbing end group. Scope and limitations of this approach are studied using monoalkyl ethers of polypropylene glycol as model polymers.