The linear growth rates of solution grown low molecular weight polyethylene single crystals have been investigated as a function of crystallization temperature, molecular weight and solution concentration. Sharp fractions were used covering the molecular weight range from 3100 to 11600. The crystals were characterized by studying (1) the equlibrium melting/dissolution temperature as a function of the molecular weight, (2) the lamellar thickness as a function of the crystallization temperature and (3) the fusion/dissolution behavior as a function of crystallization temperature. / The most interesting results are as follows: (a) The lamellar thickness varies continuously with crystallization temperature. This behavior has been interpreted to provide information on the important question of the location of the chain ends in the crystals. (b) For the higher molecular weight fractions the growth rate decreases monotonically with the crystallization temperature. In contrast for fractions in the molecular weight range of 3000 to 4000 the growth rate versus crystallization temperature curves show a notched appearance in which two branches can be distinguished. These branches intersect at a transition temperature where the temperature coefficient of the growth rates changes discontinuously. This behavior is interpreted to mean that the transition temperatures correspond to changes in the conformation of the molecules deposited on the growth faces. The growth rate data have been analyzed using current kinetic theories of polymer crystal growth. Basal surface free energies thus obtained are compared with the estimates from the relations between lamellar thickness and supercooling and melting/dissolution temperature and lamellar thickness. These results are discussed in relation to the molecular structure of the crystals.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.71824 |
| Date | January 1982 |
| Creators | Leung, Wing-Man. |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Chemistry.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 000186784, proquestno: AAINK64497, Theses scanned by UMI/ProQuest. |
Page generated in 0.0026 seconds