Title page for ETD etd-08012012-040558
|Type of Document
||Kim, Regina H.
||Siloxane modified polyurea and polyurethane urea segmented copolymers
||Master of Science
|McGrath, James E.
|Spencer, Chester W.
|Wightman, John P.
|Wilkes, Garth L.
|Date of Defense
High molecular weight polyether urea copolymers were synthesized using perfectly
difunctional aromatic amine terminated poiypropylene oxide (PPO) (2800 ) prepared
via aluminum porphorin initiated coordination polymerization. The resulting segmented
copolymer showed much higher tensile strength and better thermal stability than polyureas
based on commercial PPO which contains some terminal unsaturation. This was attributed
to the achievement of both higher molecular weight and to more extensive microphase separation
between the segments. ln addition, the surface structure of segmented polyether urea
and polyurethane urea copolymers were modified in two ways: siloxane urea segmented
copolymers were synthesized and physically blended into the system, and siloxane oligomers
of controlled molecular weight and composition were incorporated into the copolymer backbone
as a part of the soft segment. X-ray photoelectron spectroscopy (XPS) was used to obtain
surface compositional information, while differential scanning calorimetry (DSC) and
stress-strain analysis were used to characterize the bulk properties. In general, the surface
enrichment of siloxane was observed in both solvent cast blends and siloxane incorporated
systems. The surface siloxane concentration showed a small increase with siloxane segment
length, content, and surface sensitive angle. Surface segregation of these systems was suppressed
to a certain extent due to phase mixing within the copolymer bulk and by the anchoring
of both ends of the siloxane segment with urea components. The bulk properties of
these copolymer systems were not affected greatly when small amounts of siloxane ureas
were added or when small amounts of siloxane blocks were incorporated.
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