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[摘要]：By combining quartz crystal microbalance (QCM) and reflectivity, it was shown that poly(amidoamine) (PAMAM) dendrimers adsorbed at the silica water interface undergo conformational changes when incubated in various electrolyte solutions. Adsorbed dendrimers swell in solutions of high ionic strengths and low pH, while they shrink in solutions of low ionic strengths and high pH. Dendrimer swelling is further ion specific, whereby the cations influence the swelling to a larger extent than anions. Among the cations studied, magnesium ions induce largest swelling, while the lithium ions the smallest. The responsiveness to stimulus by the electrolyte composition is mainly determined by attractive electrostatic interactions between the positively charged dendrimers and the negatively charged silica substrate. The dendrimer substrate interactions are enhanced with increasing pH due to dissociation of the silanol groups at the silica surface, and they are strongly influenced by cations adsorbing on the water silica interface. The electrostatic dendrimer substrate interactions weaken in the presence of salt due to screening. |
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