Charge on a weak polyelectrolyte
Wang, Shengqin1,2; Granick, Steve3,4,5; Zhao, Jiang1
AbstractFluorescence measurements with single-molecule sensitivity are used to measure the hydrodynamic size and local pH of a weak polyelectrolyte, poly-2-vinyl pyridine end labeled with pH-sensitive dye, the polyelectrolyte having concentration so low (nanomolars) that molecular properties are resolvable only from fluorescence experiments and cannot be accessed by light scattering. We find that the local pH near the dye, inferred from its brightness, is consistently three orders of magnitude higher than the bulk pH. Upon varying the bulk pH, we measure the collapse point at which hydrophobic attraction overwhelms electrostatic repulsion between charged elements along the chain, and conclude that adding monovalent salt shifts this coil-to-globule collapse to higher pH than in the absence of salt. The influence of salt appears to shift the ionization equilibrium of this weak polyelectrolyte in the direction of the chain possessing enhanced electric charge at a given pH. Phenomenologically, this is opposite to the case for strong polyelectrolytes, although the mechanism differs.
KeywordBrightness Fluorescence Ionisation Ph Polymer Electrolytes Spectrochemical Analysis
Indexed BySCI
WOS IDWOS:000262226800002
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Document Type期刊论文
Corresponding AuthorZhao, Jiang
Affiliation1.Chinese Acad Sci, Inst Chem, Joint Lab Polymer Sci & Mat, Beijing Natl Lab Mol Sci, Beijing 100190, Peoples R China
2.Chinese Acad Sci, Grad Sch, Beijing 100039, Peoples R China
3.Univ Illinois, Dept Mat Sci, Urbana, IL 61801 USA
4.Univ Illinois, Dept Chem, Urbana, IL 61801 USA
5.Univ Illinois, Dept Phys, Urbana, IL 61801 USA
Recommended Citation
GB/T 7714
Wang, Shengqin,Granick, Steve,Zhao, Jiang. Charge on a weak polyelectrolyte[J]. JOURNAL OF CHEMICAL PHYSICS,2008,129(24).
APA Wang, Shengqin,Granick, Steve,&Zhao, Jiang.(2008).Charge on a weak polyelectrolyte.JOURNAL OF CHEMICAL PHYSICS,129(24).
MLA Wang, Shengqin,et al."Charge on a weak polyelectrolyte".JOURNAL OF CHEMICAL PHYSICS 129.24(2008).
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