Colloid and Polymer Science

, Volume 297, Issue 9, pp 1223–1231 | Cite as

Confinement effect on the aqueous behaviors of free poly(acrylic acid) and poly(acrylic acid) grafted on a nanoparticle surface

  • Kaimin ChenEmail author
  • Siyi WangEmail author
  • Xuhong GuoEmail author
Original Contribution


Poly(acrylic acid) (PAA) has recently attracted great interest in various fields, including in biomedical applications. This work compares the aqueous behaviors of two kinds of PAA in different environments. We compared free PAA (PAAfree) in an aqueous solution with PAA confined to a polystyrene nanoparticle surface (PAAconf.). The dissociation behaviors of PAA in both environments were systematically studied under various conditions, including differing ionic strengths, molecular weights of PAA, and PAA grafting density by using pH titration assays. The two key parameters concerning dissociation behaviors were obtained, namely, the degree of dissociation (α) and the dissociation constant (pKa). The results showed that the pKa was a little higher for PAAconf. than for PAAfree due to the Donnan effect. The pKa decreased with increasing ionic strength for both PAA cases due to the weakening of hydrogen bonding and the acceleration of dissociation by counterions. PAAfree with a lower molecular weight and PAAconf. with a higher grafting density showed smaller pKas, both indicating stronger dissociation abilities. To clarify this, the electromobility and zeta potential of each case were also measured, and the results confirmed the difference. Finally, bovine serum albumin (BSA) was used as a model protein to study protein-PAA interactions based on their aqueous behaviors. This work furthers our understanding of PAA behaviors in various environments and conditions, shed light on both the structural design capabilities of PAA and its further applications as a functional material.


Poly(acrylic acid) Dissociation constant Capillary electrophoresis Turbidimetric titration 



We thank LetPub ( for its linguistic assistance during the preparation of this manuscript.

Funding information

This work was supported in part by the National Natural Science Foundation of China (Grant 21504052).

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.


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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2019

Authors and Affiliations

  1. 1.College of Chemistry and Chemical EngineeringShanghai University of Engineering ScienceShanghaiPeople’s Republic of China
  2. 2.Testing CenterShanghai Research Institute of Chemical Industry Co., LtdShanghaiPeople’s Republic of China
  3. 3.State Key Laboratory of Chemical EngineeringEast China University of Science and TechnologyShanghaiPeople’s Republic of China

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