The crystallization and melting behavior of copolymers (specially of those which partially exclude the and component) has not been well understood. Poly(ether ketone ketone) PEKK is such a partially excluding copolymer in which the crystalline phase tends to exclude one of two similar monads. Previous studies on PEKK have focused on effects of changing overall composition on the melting and crystallization behavior. These studies have demonstrated that PEKK tends to exclude one of two chemically similar monads from the crystalline phase, and the crystallization and melting behavior is affected as a result of this exclusion. However, the effect of changing linear chain architectures on the thermal behavior of such copolymers has not been investigated.
In this study, the effect of changing architectures of the linear chain (blockiness) on the crystallization and melting behavior has been studied. The overall composition of the copolymer is maintained at 50% 2nd comonomer, and a series of samples prepared with different block lengths and amounts of branching. The crystallization and melting behavior of these samples is then studied using hot stage optical microscopy, scattering (small and wide angle X-ray scattering) and thermal analysis techniques (differential scanning calorimetry).
It has been demonstrated that, upon changing from an alternating to a non-alternating structure, substantial amounts of 224 component are excluded from the crystalline phase and the melting temperature is raised considerably. Further, because of increased amounts of branching which accompanies the change in blockiness, the crystallization kinetics is slowed down. These results have been analyzed in terms of existing theories of copolymer crystallization, and some speculative arguments have been presented on the factors which affect the crystallization mechanism in such partially excluding copolymers. The validity of equilibrium thermodynamics based on the enthalpic approach has been analyzed. / Ph. D.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/40130 |
| Date | 24 October 2005 |
| Creators | Verma, Ravi Kant |
| Contributors | Materials Engineering Science, Kander, Ronald G., Faron, Katherine L., Hsiao, Benjamin S., Marand, Herve, Ward, Thomas C., Wilkes, Garth L. |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | English |
| Detected Language | English |
| Type | Dissertation, Text |
| Format | xi, 110 leaves, BTD, application/pdf, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
| Relation | OCLC# 32771898, LD5655.V856_1994.V477.pdf |
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