Abstract/Details

Rheology and interfacial properties of aqueous solutions of the diblock polyelectrolyte poly(styrene -block -acrylic acid)


2007 2007

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Abstract (summary)

In aqueous solutions diblock polyelectrolytes with amphiphilic character form aggregate structures, which affect physical properties such as viscosity, elasticity, surface tension, and film hydrophilicity. Potential applications for diblock polyelectrolyte solutions include coatings, inks, oil recovery agents, personal care products, and biomaterials. By varying the diblock polyelectrolyte and solution properties, the solutions can be tuned to meet the needs of particular applications.

The research objective was to identify the influences of block length, pH, and ionic strength on the rheological and interfacial properties of poly(styrene- b-acrylic acid) (PS-PAA) solutions. Six polymers with varied PS and PAA block lengths were examined, all at 1.0 wt% in aqueous solutions. The hydrophobicity of the PS block causes the formation of spherical micelles in aqueous solutions. Increasing the solution pH ionizes the PAA block, which leads to an increase in micelle corona thickness due to repulsions between chains.

Major trends observed in the rheological and interfacial properties can be understood in terms of expected changes in the micelle size and interfacial self-assembly with pH, ionic strength, and block length. Addition of NaOH was found to increase the solution pH and initially led to increases in solution viscosity, elasticity, surface tension, and film hydrophilicity. This effect was attributed to creation of larger micelles and greater inter-micellar repulsions as the PAA chain became more fully charged. However, when the concentration of NaOH exceeded a critical value, the solution viscosity, elasticity, and film hydrophilicity decreased. It is believed this was due to charge shielding by excess sodium ions, leading to shrinkage of the micelle corona and smaller micelles. Increasing the PS-PAA solution ionic strength by adding NaCl also provided charge shielding, as observed by decreases in solution viscosity and elasticity. Increasing the length of either block led to an increase in the solution viscosity, presumably due to formation of larger micelles and hence an increased effective micellar volume fraction. The dependence of the interfacial properties on block length was less straightforward. The solution surface tension and film hydrophilicity were both found to correlate well with the ratio of styrene units to acrylic acid units.

Indexing (details)


Subject
Polymers;
Chemical engineering;
Materials science
Classification
0495: Polymers
0542: Chemical engineering
0794: Materials science
Identifier / keyword
Applied sciences; Pure sciences; Diblock; Interfacial; Poly(styrene-block-acrylic acid); Polyelectrolyte; Rheology
Title
Rheology and interfacial properties of aqueous solutions of the diblock polyelectrolyte poly(styrene -block -acrylic acid)
Author
Kimerling, Abigail
Number of pages
220
Publication year
2007
Degree date
2007
School code
0118
Source
DAI-B 68/03, Dissertation Abstracts International
Place of publication
Ann Arbor
Country of publication
United States
Advisor
Bhatia, Surita R.; Rochefort, Willie E. "Skip"
University/institution
University of Massachusetts Amherst
University location
United States -- Massachusetts
Degree
Ph.D.
Source type
Dissertations & Theses
Language
English
Document type
Dissertation/Thesis
Dissertation/thesis number
3254927
ProQuest document ID
304846165
Copyright
Database copyright ProQuest LLC; ProQuest does not claim copyright in the individual underlying works.
Document URL
http://search.proquest.com/docview/304846165
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