Calorimetric study of the adsorption of poly(ethylene oxide) and poly(vinyl pyrrolidone) onto cationic nanoparticles

Naa Larteokor McFarlane, Norman J. Wagner, Eric W. Kaler, Matthew L. Lynch

Research output: Contribution to journalArticlepeer-review

22 Scopus citations

Abstract

The adsorption of two polymers, poly(ethylene oxide) (PEO) and poly(vinyl pyrrolidone) PVP, onto cationic nanoparticles suspended in both water and a buffer solution is studied via isothermal titration calorimetry (ITC). These are model systems studied previously to understand polymer-induced phase separation and bridging flocculation in the protein limit. ITC measurements provide critical information for rationalizing the effects of polymer type and added buffer solution on the loss of stability of nanoparticle-polymer solutions. For PEO, weak segmental adsorption energies of ∼0.2kBT for PEO in water and buffer are consistent with depletion phase separation. For PVP in water, segmental adsorption energies on the order of ∼1.6kBT support the observed bridging flocculation, whereas a weaker adsorption energy of ∼0.7kBT for PVP in buffer is consistent with depletion phase separation. Multilayer adsorption is observed in buffer solutions, which corroborates a measured increase in the hydrodynamic size of the polymer-nanoparticle complexes with added buffer. The entropy of adsorption is calculated from equilibrium constants determined by combining ITC and adsorption isotherms.

Original languageEnglish (US)
Pages (from-to)6262-6267
Number of pages6
JournalLangmuir
Volume26
Issue number9
DOIs
StatePublished - May 4 2010

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