Concentrated solutions of hydroxypropylcellulose in aqueous and in polar organic solvents form lyotropic liquid crystalline phases. The critical concentration of hydroxypropylcellulose needed for anisotropic phase separation is dependent upon the solvent and is much greater than that expected for rod-like species in solution. The flexibility of the cellulosic chains in a particular solvent is believed to be the main factor governing the critical hydroxypropylcellulose volume fraction at phase separation. The anisotropic phase exhibits birefringence, iridescence, and very high optical activity, properties characteristic of cholesteric liquid crystals. The helicoidal pitch for most of these cholesteric samples in water and organic solvents varies from 280 to 700 nm, but in certain organic solvents the helicoidal pitch ranges up to 6000 nm. The latter samples exhibit fingerprint-like periodicity lines in the light microscope and distinctive "shimmering" colors. For both types of samples the helicoidal pitch is found to vary inversely with the third power of the hydroxypropylcellulose volume fraction. A model is proposed for the cholesteric structure in which the average separation, d, between the chain molecules varies with (phi)(,2)('- 1/2), where (phi)(,2) is the polymer volume fraction. The experimental x-ray diffraction data are in accord with this relationship. The angular twist between the molecules in adjacent cholesteric layers is calculated to vary from 0.30 to 1.8(DEGREES) over the mesophase concentration range investigated. / Light scattering measurements give twice the weight average molar mass for hydroxypropylcellulose as do sedimentation equilibrium measurements. Viscosity measurements in organic solvents show that the hydroxypropylcellulose conformation in dilute solution is neither that of a random coil nor that of a rigid rod. All aqueous hydroxypropylcellulose solutions show a lower consolute temperature that varies more with the sample molar substitution than with its molar mass. A qualitative "phase" diagram for aqueous hydroxypropylcellulose solutions is also included.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.77155 |
| Date | January 1982 |
| Creators | Werbowyj, Rita Stephania. |
| 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: 000139377, proquestno: AAINK58126, Theses scanned by UMI/ProQuest. |
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