Abstract/Details

Phase separation *kinetics of polyelectrolyte solutions


2006 2006

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Abstract (summary)

The kinetics of phase separation of sodium Poly(styrene sulfonate) (NaPSS) in water with barium chloride (BaCl2) was studied by static and dynamic light scattering. This polyelectrolyte system shows an upper critical solution temperature behavior, such that the solutions are homogeneious at temperatures above the phase boundary. Using dynamic light scattering, two diffusive modes were detected, and unaggregated polyelectrolyte chains and aggregates coexist in the homogeneous phase.

The hydrodynamic radius (RH) of the unaggregated chains is of the order of 1 to 10 nm depending on the molecular weight of NaPSS, while RH of aggregates is of the order of 100 nm independent of the molecular weight of NaPSS. Unaggregated chains follow good solution behavior with a fractal dimension of 5/3. On the other hand, the fractal dimension of aggregates is larger than 3.5. The value of the fractal dimension suggests that the structure of aggregate is similar to branched polymers, such as star polymers.

Upon rapidly cooling the NaPSS sample below the phase boundary, phase separation takes place. During the initial stage, unaggregated chains were converted to aggregates. Newly generated aggregates have a similar fractal dimension and size to aggregates found above the phase boundary. The size of aggregates remained constant while the number of aggregates increased. During the initial stage, nucleation time is sensitive to quench depth and salt concentration. Either deepening a quench depth or increasing BaCl 2 concentration shortened the nucleation time. After the nucleation time, the size of aggregates grew linearly with time. This marks the growth period, at which time the growth rate is higher for deeper quench depths and higher BaCl2 concentrations. The mechanism of phase separation of NaPSS in water and BaCl2 is similar to the nucleation and growth mechanism where the aggregate serves as a nucleus. However, it is different from conventional nucleation and growth theory in that the nucleus already exists above the phase boundary.

Indexing (details)


Subject
Polymers;
Condensation
Classification
0495: Polymers
0611: Condensation
Identifier / keyword
Pure sciences, Aggregation, Kinetics, Phase separation, Polyelectrolyte
Title
Phase separation *kinetics of polyelectrolyte solutions
Author
Kanai, Sonoko
Number of pages
129
Publication year
2006
Degree date
2006
School code
0118
Source
DAI-B 67/11, Dissertation Abstracts International
Place of publication
Ann Arbor
Country of publication
United States
ISBN
9780542978081
Advisor
Muthukumar, Murugappan
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
3242362
ProQuest document ID
305303192
Copyright
Database copyright ProQuest LLC; ProQuest does not claim copyright in the individual underlying works.
Document URL
http://search.proquest.com/docview/305303192
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