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The elution behavior of different solvent/polymer systems has been studied by means of size‐exclusion chromatography (SEC) in two organic column packings based on polystyrene/divinylbenzene (PS/DVB) copolymer, named μ‐styragel and TSK‐Gel HHR. Both packings offer similar characteristics (pore size, particle size, efficiency) but some differences arise when eluting the same systems. The different elution behavior observed in both polymeric gels has been analyzed in terms of their swelling and crosslinking degrees. To evaluate the magnitude of these parameters, a new equation is proposed which has been derived from the Flory‐Huggins theory of swelling equilibrium, and takes into account binary and ternary thermodynamic interaction functions. The equation appropriately predicts the experimental results, showing that the gel that exhibits more solute‐packing attractive interactions (or adsorption as secondary mechanism) is also the one with the highest crosslinking degree or lowest swelling ratio. In this sense, the μ‐styragel column was the most crosslinked polymer network. In addition, the influence of solvent nature, polymer nature, and solute composition on the observed swelling degree has also been compared in both packings.

Water-dispersible upconversion nanoparticles (β-NaYF4:Yb(3+),Er(3+), UCNP) coated with a thin shell of a biocompatible copolymer comprising 2-hydroxyethylmethacrylate (HEMA) and 2-acrylamido-2-methyl-1-propanesulphonsulphonic acid (AMPS), which we will term COP, have been prepared by multidentate grafting. This capping is remarkably resistant to strong acidic conditions as low as pH 2. The additional functionality of the smart UCNP@COP nanosystem has been proved by its association to a well-known photosensitizer (namely, methylene blue, MB). The green-to-red emission ratio of the UC@COP@MB nanohybrid exhibits excellent linear dependence in the 7 to 2 pH range as a consequence of the release of the dye as the pH decreases.