Solvent structuring in water-acetone poly--caprolactone mixtures and its effect on the polymer structure and processability

Nicodemo Di Pasquale, Daniele Marchisio, Antonello Barresi, Paola Carbone

    Research output: Contribution to journalArticlepeer-review


    One of the most common processes to produce polymer nanoparticles is the solvent-displacement method, in which the polymer is dissolved in a “good” solvent and the solution is then mixed with an “anti-solvent”. The polymer processability is therefore determined by its structural and transport properties in solutions of the pure solvents and at the intermediate compositions. In this work, we focus on poly-ε-caprolactone (PCL) which is a biocompatible polymer that finds widespread application in the pharmaceutical and biomedical fields, performing full atomistic molecular dynamics simulations of one PCL chain of different molecular weight in a solution of pure acetone (good solvent), of pure water (antisolvent), and their mixtures. Our simulations reveal that the nanostructuring of one of the solvents in the mixture leads to an unexpected identical polymer structure irrespectively of the concentration of the two solvents. In particular, although in pure solvents the behavior of the polymer is, as expected, very different, at intermediate compositions, the PCL chain shows properties very similar to those found in pure acetone as a result of the clustering of the acetone molecules in the vicinity of the polymer chain. We derive an analytical expression to predict the polymer structural properties in solution at different solvent compositions and show that the solvent clustering affects in an unpredictable way the polymer diffusion coefficient. These findings have important consequences on the optimization of the nanoparticle production process and in the implementation of continuum modeling techniques to model it.
    Original languageEnglish
    Pages (from-to)13258-13267
    Number of pages9
    JournalThe Journal of Physical Chemistry Part B: Condensed Matter, Materials, Surfaces, Interfaces & Biophysical
    Issue number46
    Publication statusPublished - 2014


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