Abstract/Details

Diblock-copolymer melts at patterned surfaces and dilute polymer solutions under shear


1999 1999

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Abstract (summary)

Diblock-Copolymer Melts at patterned surfaces are investigated. Above the order-disorder transition (ODT) of the bulk, density-functional theory is used to calculate the density profile at the surface. Below the ODT self-consistent field theory (SCFT) is employed to extract numerically possible density variations across a thin film. The orientation of the diblocks and lamellar morphology at the surface depends on the ratio of natural lamellar bulk period to surface period [special characters omitted]. The diblocks can be either perpendicular or parallel to the surface, inducing parallel or perpendicular lamellar morphology.

Individual polyelectrolytes and their counterions are studied with SCFT. Scaling behavior and density distribution are numerically calculated and compared to known results. Although the scaling roughly agrees with expected results, the density distribution and the end-to-end vector distribution do not. Apparently, fluctuations significantly contribute to angular averaged SCFT of an individual polymer.

Dilute polymer solutions under shear are investigated with renormalization group theory of the Gaussian model and with Brownian dynamics simulations of the bead-rod model. The material functions derived from the first model using coupled Langevin equations agree qualitatively with the ones derived from the diffusion equation of the same model. They exhibit shear thickening for high shear rates due to the unrestricted extensibility of the chain. The excluded volume interaction is responsible for shear thinning at intermediate shear rates. The simulations yield shear thinning behavior for all shear rates, independent of the presence or absence of excluded volume or hydrodynamic interactions. A good agreement with experiments is obtained for the relative extension with increasing shear rate. In theta-solutions an unexpected shrinkage of the chain is observed for high shear rates.

Indexing (details)


Subject
Condensation;
Polymers;
Chemistry
Classification
0611: Condensation
0495: Polymers
0494: Chemistry
Identifier / keyword
Pure sciences; Diblock-copolymer; Melts; Patterned surfaces; Polymer; Shear
Title
Diblock-copolymer melts at patterned surfaces and dilute polymer solutions under shear
Author
Petera, Dirk
Number of pages
114
Publication year
1999
Degree date
1999
School code
0118
Source
DAI-B 60/02, Dissertation Abstracts International
Place of publication
Ann Arbor
Country of publication
United States
ISBN
9780599199705, 0599199709
Advisor
Muthukumar, M.
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
9920640
ProQuest document ID
304514920
Copyright
Database copyright ProQuest LLC; ProQuest does not claim copyright in the individual underlying works.
Document URL
http://search.proquest.com/docview/304514920
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