Memorial University DAI: Molecular orientation and dynamics of flexible polymers in strongly deforming flow fields

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Title	Molecular orientation and dynamics of flexible polymers in strongly deforming flow fields
Author	Kilfoil, Maria, 1970-
Description	Thesis (Ph.D.)--Memorial University of Newfoundland, 2001. Physics and Physical Oceanography
Date	2001
Pagination	vi, 151 leaves : ill.
Subject	Nuclear molecules; Complex fluids; Nuclear magnetic resonance
Degree	Ph.D.
Degree Grantor	Memorial University of Newfoundland. Dept. of Physics and Physical Oceanography
Discipline	Physics and Physical Oceanography
Language	eng
Notes	Bibliography: leaves [143]-150
Abstract	A method of spatially resolved magnetic resonance spectroscopy has been developed to allow studies of order and dynamics in complex fluids having transverse relaxation times on the order of tens of milliseconds, studies which were otherwise not possible using existing techniques. The model of Doi and Edwards is a microscopic description for stress transmission in concentrated polymer solutions and melts under deformation. Central to the Doi-Edwards model is the dependence of the stress on bond orientational order of the chain segments. Different elements of the segmental alignment tensor for a polymer melt under strong shearing flow are measured here using localized deuterium NMR spectroscopy on a 61 OK molecular weight poly (dimethyl siloxane) melt in a concentric cylinder Couette rheometric cell. This approach provides a new means of testing the Doi-Edwards model and its refinements, in the important regime far from equilibrium where the entangled polymers exhibit nonlinear viscoelastic behaviour. -- The same rheo-NMR methodology is also used to test predictions of the model of Leslie and Ericksen which describes director dynamics in semi-flexible rod-like polymers subjected to viscous stresses. Director dynamics are studied in a lyotropic liquid crystal polymer PBLG (300K) in a highly ordered, nematic phase in a planar extensional flow around a stagnation point. In addition, bulk 2H NMR studies are carried out on PBLG under shear, in concentric cylinder Couette and cone and plate rheometric cells. Magnetic alignment (equivalent to the dynamic Freedericksz transition) is investigated in all three cells following deformation. Values are obtained for the Leslie viscosity coefficients a2 and a3, scaled by the diamagnetic susceptibility. Possible development of mesoscale structure under shear is discussed.
Type	Text
Resource Type	Electronic thesis or dissertation
Format	Image/jpeg; Application/pdf
Source	Paper copy kept in the Centre for Newfoundland Studies, Memorial University Libraries
Local Identifier	a1541760
Rights	The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission.
Collection	Electronic Theses and Dissertations
Scanning Status	Completed
PDF File	(17.23 MB) -- http://collections.mun.ca/PDFs/theses/Kilfoil_Maria.pdf
CONTENTdm file name	197338.cpd