Abstract/Details

An investigation of the importance of screening effects in polymer solutions and blends


2005 2005

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Abstract (summary)

In this work the importance of screening effects in both polymer solutions as well as polymer blends will be investigated. It is essentially a natural extension of earlier work in this group with functionalized polymer blends, where it was proposed that the number of intramolecular contacts far exceeded what one would expect from the classical mean field theory. Models with varying degrees of complexity were investigated, where intramolecular contacts, in each case, were treated explicitly.

First a very simple modification of the classical Flory-Huggins theory is investigated, and it is shown that it is possible to reproduce the concentration dependence of the interaction parameter in polymer solutions with surprising accuracy. It is also shown that the calculated spinodals were in good agreement with experimentally reported data, especially at higher molecular weights.

Free volume effects are then accounted for through a modification of the Flory-Orwoll-Vrij Equation of State model. The model was tested for a number of systems at &thetas;-conditions as well as non &thetas;-conditions, for its ability to reproduce the concentration dependence of the interaction parameter, using solubility parameters as well as internal pressures, with varying degrees of accuracy.

Another simple modification of the Flory-Huggins theory for polymer blends is presented. It is shown that the model is able to reproduce the very peculiar phenomenon observed in the behavior of the interaction parameters determined from Small Angle Neutron Scattering (SANS) in isotopic polymer blends, by varying the screening factor for one of the components by less than 3%.

Finally it is shown that a further modification to accommodate copolymer blends, leads to a model which is equally well equipped to describe the strong concentration dependence of the interaction parameter observed experimentally. In these calculations, it is assumed that the copolymers can treated as homopolymers. Since only isotopic copolymer systems were investigated it is presumably a safe assumption. It was found that a small change of less than 4% in the screening factor of one of the components was enough to obtain extremely good correspondence with the experimentally observed data.

Indexing (details)


Subject
Materials science;
Polymers
Classification
0794: Materials science
0495: Polymers
Identifier / keyword
Applied sciences; Pure sciences; Interaction parameters; Polymer blends; Polymer solutions; Screening; Solubility
Title
An investigation of the importance of screening effects in polymer solutions and blends
Author
Berg, Lennart P.
Number of pages
257
Publication year
2005
Degree date
2005
School code
0176
Source
DAI-B 66/05, Dissertation Abstracts International
Place of publication
Ann Arbor
Country of publication
United States
ISBN
9780542115714, 0542115719
Advisor
Painter, Paul C.
University/institution
The Pennsylvania State University
University location
United States -- Pennsylvania
Degree
Ph.D.
Source type
Dissertations & Theses
Language
English
Document type
Dissertation/Thesis
Dissertation/thesis number
3173777
ProQuest document ID
305445102
Copyright
Database copyright ProQuest LLC; ProQuest does not claim copyright in the individual underlying works.
Document URL
http://search.proquest.com/docview/305445102
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