Carboxylated core–shell particles: II. Experimental and theoretical comparison of salt-induced swelling

In a previous work [1] we showed that the swelling behavior of carboxylated core–shell particles (PS–PC) can be modified using a specific sample preparation route or favoring the hydrophobic attractive interaction by other way, i.e. controlling the temperature. In that paper, we found that the swelling was promoted in those particles which were initially in a highly swollen state (pH ⩾ 10) while it was hindered for those particles which were not previously in this trigger pH. In this work, we present a discussion of the salt-induced swelling of the same carboxylated core–shell system (PS–PC) with two tuned swelling behaviors: the former, called A-2, exhibits promoted swelling while in the latter, called B-1, the swelling is greatly suppressed because of a compact conformation of the polymer shell is induced [1]. Good agreement between experimental, numerical and theoretical results at all pH values is obtained for promoted particles (A-2). On the other hand, the salt-induced swelling behaviors shown by hindered particles (B-1) corroborate that polymer restructuring includes assembly among ionic groups which affect their ionization degree and also the electrosteric interaction between particles. Finally, the salt-induced swelling behavior shown by the B-1 system at pH 8.6 resembles the Pincus regime predicted by scaling theory.

The same core-shell particles can exhibit different salt-induced behavior depending of the preparation history, i.e. depending on whether a compact or stretched conformation of the polymer shell was induced.Figure optionsDownload high-quality image (164 K)Download as PowerPoint slideResearch highlights
► The swelling of carboxylated core–shell particles can be tuned.
► Salt-induced swelling of promoted particles (A-2) follows the SCF theory.
► Promoted particles at pH = 10 behave as a quenched brush.
► Hindered particles (B-1) at pH = 8–10 behave as an annealed brush.
► B-1 swelling (at pH = 8.6) resembles the predicted Pincus regime (as yet unobserved).