Past exam of the chemistry course of the year 4 of the natural sciences course of the University of Cambridge / 2022 / Paper 1 / 5 / c

There is no universal ranking from the information supplied. The depletion force scales with polymer osmotic pressure, hence with $\rho$ in the ideal model. London dispersion forces instead depend on the material-dependent Hamaker constant, the intervening solvent, the closest approach and the contact geometry.

Close face contact can give a strong dispersion contribution; the ideal continuum expression even becomes singular without a molecular-distance cutoff. Nevertheless, refractive-index matching can greatly reduce that contribution, and increasing polymer concentration can strengthen depletion force. A quantitative comparison requires those missing material and concentration scales. The two attractive contributions may act together.